So hat die International Diabetes Federation im Jahr einen erhöhten Bauchumfang als eines der Kriterien für die Diagnostizierung des Metabolischen Syndroms festgelegt. Induction of mutations and chromosome aberrations in lung cells following in vivo exposure of rats to nitrogen oxides. Oktober um The protocol adopted for the study was that of the ECRHS but the age range studied was larger 20—70 years. Dem widerspricht nun aber die bislang umfassendste, veröffentlichte Studienauswertung, der zufolge bereits bei einem BMI oberhalb 25 die Risiken für koronare Herzkrankheit, Schlaganfall, Atemwegserkrankungen und Krebs allesamt erhöht sind und mit jedem weiteren Kilo weiter ansteigen.
High nitrogen dioxide concentrations are also associated with the use of candles and mosquito coils. The link between direct source exposure and high nitrogen dioxide levels was noted in a small study of unvented natural gas fireplaces mean Indoor concentrations of nitrogen dioxide are also subject to geographical, seasonal and diurnal variations.
Differences in the indoor concentrations in various countries are mainly attributable to differences in the type of fuel used for cooking and heating and the rate of fuel consumption.
While few studies have included repeated measurements of indoor nitrogen dioxide levels, it is known that within-home variability can be significant owing to the various contributing factors discussed above Seasonal variability can be significant, owing to variations in source use e. This variability results typically in higher indoor concentrations during winter months 31 , 45 , This variability, and its principal determinants, should be considered when extrapolating from exposure estimates determined using daily or weekly measurements to estimates of annual exposures.
Since few if any studies have directly measured annual averages of indoor nitrogen dioxide concentrations, periodic measurements across seasons would be needed to construct representative estimates of long-term exposure.
As nitrogen dioxide is a free radical, it has the potential to deplete tissue antioxidant defences and, as a consequence, cause injury and inflammation as shown in a variety of in vitro test systems. More recently, Olker et al. This was explained by decreased production as a result of an inhibition of NADPH oxidase and complex III of the respiratory chain, and to a lesser extent increased scavenging brought about by enhanced glutathione peroxidase and CuZn-superoxide dismutase mRNA expression and enzyme activities.
Cell culture systems have also been used to describe nitrogen-dioxide-mediated cell injury and inflammation. It should be remembered that confluent airway epithelial cell monolayers in vitro are not fully differentiated and posses a markedly decreased level of resistance to pollutants when compared to the epithelium in the intact human.
The combination of cytokine treatment and nitrogen dioxide exposure consistently enhanced the generation of nitric oxide and IL Cells were found to undergo apoptotic cell death during the early post-nitrogen-dioxide period, independent of any significant increase in caspase-3 activity, while necrotic cell death was more prevalent at later time intervals. Exposed cells also exhibited increased expression of heme oxygenase-1 HO-1 , a redox-sensitive stress protein, at 24 hours and increased adhesion to neutrophils, which in turn resulted in an increased NHBE cell death.
Earlier reports of an involvement of nitric oxide 53 were supported by the significant decrease in cell death and neutrophil adhesion in the presence of nitric oxide synthase inhibitors L-NAME and 3-aminoguanidine Such effects vary widely, however, depending on the species and strain exposed, the concentration and duration applied, and the age and sex of the animals In extrapolating the aforementioned data to humans, it is the anatomical and physiological differences between animals and humans that represent a particular challenge.
For example, we have known for some time from mathematical modelling that the distribution of nitrogen dioxide deposition within the respiratory tract of rats, guinea-pigs, rabbits and humans appears to be similar 56 — More recently however, Tsujino et al. Despite some limitations, owing to many simplifications and assumptions necessary to construct the airway model and carry out calculations, intra-airway nitrogen dioxide concentrations were higher in the upper and lower airways of humans compared with rats and dogs, while those in the alveolar regions were lowest in humans.
A notable exception is the effect on lung lipid metabolism. Effects on both lipid and antioxidant metabolism showed a response pattern that depends on both concentration and duration of exposure Frequently observed features at higher nitrogen dioxide levels include the induction of lung oedema, an increase in antioxidant metabolism, an increase in lung enzymes associated with cell injury, and changes in lung lipids.
In relation to nitrogen-dioxide-induced oxidative stress and perturbations in antioxidant metabolism, a potential protective role that antioxidant status may play in influencing the lung response to pollutant exposure has been explored The effects of a low-selenium diet 1. Although still not fully understood, alterations in pulmonary metabolism may be early signs of cell lesions, which become manifest only at higher concentrations or upon longer exposure 60 — 62 , 68 , We do, however, appreciate that both the exposure regimen used and the time of exposure are important.
In a subchronic study of lung lesions in rats, Rombout et al. Other experiments have addressed the temporal pattern of nitrogen dioxide effects and found them to be complex For example, over a 7-day period, a wave of epithelial hyperplasia occurs, peaking by about day 2 Long-term exposure to nitrogen dioxide leads to emphysema-like structural changes in animals, in addition to thickening of the alveolar capillary membrane, loss of ciliated epithelium and increases in lung collagen.
Such changes have been observed in mice, rats, dogs and monkeys 60 — 62 , In , the USEPA reviewed 23 research reports on nitrogen dioxide exposure and emphysema to determine whether the effects reported met the US National Heart, Lung, and Blood Institute definition for human emphysema This can be important because the animal studies were of interest for the purposes of extrapolation to humans, whether or not the more rigorous definition of human emphysema which includes destruction of alveolar walls is met.
Nevertheless, three studies reported convincing evidence of human-type emphysema following exposure to very high nitrogen dioxide levels relative to ambient concentrations: After this post-exposure period, lung morphometry studies showed changes analogous to human centrilobular emphysema. Increased lung collagen deposition was identified within the respiratory bronchiolar submucosa, although this was only significant in the higher-dose group The main findings were progressive airway inflammation with a marked influx of neutrophils and macrophages, goblet cell hyperplasia indicative of increased mucus hypersecretion in the central airways, progressive airflow obstruction and focal parenchymal inflammation associated with airspace enlargement.
These changes led to accelerated lung growth, characterized by an imbalance in the relative composition of the extracellular matrix, but failed to induce emphysema. Indeed, although airspace enlargement was evident, nitrogen dioxide resulted in an increase in the total surface area and absolute volume of alveolar walls comprising all compartments.
An increase in lung volume and compliance was seen at 3 weeks but not at 6 weeks in neonatal rats exposed to an identical regimen In guinea-pigs exposed to The effects of short-term hour exposure to nitrogen dioxide on airway eosinophilic inflammation and bronchial hyperreactivity have been examined using a standard murine model of antigen-modified broncho-constriction and airway inflammation Nitrogen dioxide was found to enhance epithelial damage, reduce mucin expression and increase baseline smooth muscle tone.
Although a modest increase in airway neutrophilia was detected, exposure was not associated with airway eosinophilia or with an increase in bronchial hyperresponsiveness. In contrast, Poynter et al. Findings included acute damage associated with inflammation and lesions in the alveolar duct region and an influx of macrophages and neutrophils into the lavageable air spaces.
Moreover, 20 days after cessation of the inhalation regimen, eosinophilic and neutrophilic inflammation, pulmonary lesions and airway hyperresponsiveness were still present. Following the final challenge with ovalbumin, mice developed eosinophilic inflammation, mucus cell metaplasia, airway hyperresponsiveness and antigen-specific IgE and IgG1, and Th2-type cytokine responses. The authors likened these changes to the phenotypic alterations in allergic asthma and those elicited following ovalbumin challenge in antigen-sensitized mice.
In contrast, IL, IL-6 and suppressor of cytokine signalling-3 protein were elevated. Analyses of highly purified alveolar macrophages indicated that changes in the activation state of these cells were most likely responsible for the observed effects. To increase our understanding of the contribution of nitrogen dioxide to the development of COPD, Brandsma et al.
Nitrogen dioxide exposure increased goblet cells, eosinophils and the levels of IL-6, while it reduced the levels of IL Four weeks of nitrogen dioxide, cigarette smoke or both was not sufficient to induce significant emphysema, nor did it lead to lower numbers of lymphocytes, neutrophils or macrophages in lung tissue. The authors suggested that these attenuating effects may be due to modulating effects of nitrogen dioxide on cytokine production by macrophages and epithelial cells.
Clearly, cigarette smoke contains a range of radical species, including nitrogen dioxide, and these data may simply reflect the induction of similar pathways by both challenges.
Several types of animal study have indicated that nitrogen dioxide increases susceptibility to respiratory infections 60 , 61 , 88 — An extensive set of data was collected using the infectivity model, which measures the total antibacterial defences of the lungs of mice.
Other studies have shown that peak and patterns of nitrogen dioxide exposure are important in determining response 60 , 79 , For example, Miller et al. The extrapolation of these findings to humans cannot be made directly, because most of the studies used pneumonia-induced mortality as an end-point. However, the infectivity model reflects alterations in the defence mechanisms of mice that are shared by humans. Nevertheless, the quantitative relationship between effective nitrogen dioxide levels in animals and in humans is unknown.
Although numerous studies provide evidence of the effects on the systemic humoral and cell-mediated immune systems, these studies are difficult to interpret 60 , The association between exposure to common air pollutants, including nitrogen dioxide, and altered host immunity to respiratory viral infections has recently been reviewed Two studies by Rose et al. The mice exposed to nitrogen dioxide not only required fold less virus to become infected possibly due to reduced phagocytosis and macrophage destruction of the virus in the pollutant-exposed mice but were more likely to be re-infected with murine cytomegalovirus, suggesting that exposure can adversely affect the development of virus-specific immunity.
There are no reports among the limited number of carcinogenicity studies that nitrogen dioxide causes malignant tumours or teratogenesis 60 , 61 , 96 , Genotoxicity studies in vivo have produced mixed results. Numerous studies of the interaction of nitrogen dioxide with other air pollutants, predominantly ozone, show that the effects are due to ozone alone, are additive or are synergistic, depending on the end-point and exposure regimen The mature rats that were exposed to diesel exhaust from gestational day 7 to delivery showed a decrease in the daily production of sperm due to an insufficient number of Sertoli cells.
All exhaust-exposed groups showed almost the same reactions to the inhalation, indicating that the gaseous phase must have included the responsible toxicants; these were not identified, although nitrogen dioxide would be a major constituent. Experimental animal work on the health effects, and mechanisms thereof, of nitrogen dioxide has not focused on indoor sources or exposure patterns of the pollutant other, of course, than to have conducted all studies in an indoor environment.
As such, in addition to newly published work, the studies reviewed in this section include those described in WHO's latest guidelines for ambient nitrogen dioxide Subchronic and chronic exposures weeks to months to low levels, however, cause a variety of effects, including alterations to lung metabolism, structure and function, inflammation and increased susceptibility to pulmonary infections.
It is apparent from both in vitro and animal toxicology studies which toxic effects of nitrogen dioxide might occur in humans. Nevertheless, owing to a the frequent use of extremely high exposure concentrations in experimental studies, b the inherent differences between mammalian species and c the dearth of information available on tissue response of different species to a given dose of nitrogen dioxide, it is difficult to extrapolate quantitatively, with any degree of confidence, the effects that are actually caused by a specific inhaled dose or concentration.
An important point, worthy of consideration, is the possible interaction between nitrogen dioxide and other indoor pollutants. It is increasingly acknowledged by indoor environmental scientists that it is the reactions between primary pollutants, creating secondary pollutants indoors, that are probably responsible for adverse health effects.
A plethora of outdoor studies have examined the health effects of exposure to outdoor nitrogen dioxide. While there are concerns that some of the associations reported for health effects and outdoor nitrogen dioxide may be explained by co-pollutants, extensive reviews have concluded that respiratory health is associated with nitrogen dioxide exposure, independently of these other exposures 15 , Outdoor nitrogen dioxide is increasingly being implicated in a wide range of disorders.
There is also an increasing interest in the role of outdoor pollution with reproductive outcomes A full review of these is beyond the scope of this report. Studies in which exposure to nitrogen dioxide has been carefully controlled in small numbers of selected participants have been reviewed in several previous publications 15 , 62 , These studies have examined symptoms, changes in pulmonary function and changes in airway reactivity in healthy volunteers and in those with pre-existing lung disease.
Some studies have included bronchoalveolar lavage following exposure and have provided information on the inflammatory changes that may occur. There are some inconsistencies in the results of these studies but studies on healthy volunteers can be summarized as follows.
Results from controlled exposure to nitrogen dioxide in those with pre-existing lung disease can be summarized as follows. Another approach is to directly examine health effects following exposure to cooking with gas.
In a chamber study, nine adults and eleven children with asthma were exposed to nitrogen dioxide alone and then nitrogen dioxide with combustion products from a gas heater for a one-hour period Symptoms, lung function and airway reactivity were monitored. The authors concluded these exposures were not associated with clinically relevant health effects. Overall, these controlled human clinical studies, many of which were conducted more than 20 years ago, have examined the health effects of acute and often very high levels of exposure to nitrogen dioxide rather than the chronic, low-dose exposures experienced by most human populations.
Notwithstanding this, however, they suggest that those who are sensitized or who have asthma may be at particular risk of health effects from exposure to nitrogen dioxide at levels that may be experienced for short periods when individuals are near an unvented combustion appliance.
Epidemiological studies on health effects of indoor nitrogen dioxide exposure were identified from several electronic searches and by hand searching references in former reviews by WHO 15 and EPA We excluded studies that referred to solid fuel use, as this source is often also associated with high levels of particulate matter.
We also excluded studies with purely descriptive results or in which no attempt had been made to adjust for potential confounders.
In December , a similar search strategy was adopted in order to identify reports published during the period of the review. We found 72 studies with indoor measurements and evaluation of health effects up to January Three of these were related to the same study, and here we used the newer results or the publication with the analysis of the most complete sample.
An update of the search found two more publications up to December Among the remaining 71 studies, we focused on 35 studies on respiratory symptoms and disease, because this outcome was most often significantly related to nitrogen dioxide exposure and permitted the evaluation of concentrations for setting guidelines. Of these 35 studies, 20 were in children, 5 in adults and 10 in asthmatics children and adults.
In addition, studies that examined the health effects of indoor gas appliances were identified through hand searches of earlier reviews of the topic, citations within the papers identified on health effects of nitrogen dioxide, and papers known to the expert group.
As there has been some concern that susceptibility may vary with age, the epidemiological studies are presented in two sections — studies in children and studies in adults. Estimates of health effects from studies in which direct measurements of indoor nitrogen dioxide have been made are included in Table 5. Studies that have examined associations between respiratory symptoms and indoor measurements of or personal exposure to nitrogen dioxide.
Health effects in infants: There have been concerns that infants may be at particular risk of symptoms with high indoor nitrogen dioxide levels because of their high minute volume in relation to body size and because they are likely to spend a large proportion of their time indoors. A large cross-sectional study of infants aged 3—12 months taking part in a birth cohort study showed no association of two-week average bedroom nitrogen dioxide median Of the 20 infant symptoms examined, only diarrhoea was associated with indoor nitrogen dioxide levels adjusted odds per doubling of 1.
More recently, a nested case control study of infants taking part in a birth cohort study was conducted in Oslo, where gas appliances are not used indoors for heating or cooking and levels of indoor nitrogen dioxide are low However, data from a birth cohort study in Sweden where, again, indoor gas appliances are rare , using a similar nested case control design, suggested an association of recurrent wheezing up to the age of two years with mean four-week living room nitrogen dioxide There was an increased risk OR 1.
However, the reported associations are below conventional levels of statistical significance. Another study in Scandinavia, but this time based in Copenhagen, showed no association of bedroom nitrogen dioxide levels mean level 8. Populations of infants with higher exposure to indoor nitrogen dioxide were examined in a three-centre birth cohort study.
Two-week average median and 75th centile living room nitrogen dioxide in each of the three centres Ashford, Kent, United Kingdom Researchers in the Menorca centre went on to examine associations of neurocognitive status in four-year-old children with level of exposure to nitrogen dioxide as measured at three months A negative association of poor cognition with nitrogen dioxide was observed a decrease of 0.
This was particularly seen in children with the GSTP1—Val allele, a genetic polymorphism that may lead to reduced antioxidant defences within the developing brain. The authors stated that confounding by other pollutants such as particulates could not be ruled out, particularly as many of the homes were using bottled gas.
Unfortunately, the other centres taking part in the study do not have the necessary outcome information to try to replicate this observation. Two publications based on a longitudinal study of infants in Connecticut examined lung health and its association with indoor gas appliances and indoor nitrogen dioxide levels 40 , Participants were selected if, at birth, their mother reported she had another child under the age of 11 years who had asthma. In the infants included in the first report, living in a home with a gas stove was associated with an increased risk of persistent cough OR 1.
These children had asthmatic siblings and might be considered to be a genetically susceptible group, but the associations were only seen in children whose mother did not have asthma. Forty-five per cent of the infants were living in homes with a two-week average living room nitrogen dioxide level greater than In the second report, mothers of about newborn infants recorded each day their infants' respiratory symptoms during the first year of life.
Two-week mean living area nitrogen dioxide was measured concurrently with nitrous acid interquartile range 9. In single-pollutant models, a dose-dependent association of the number of days with wheeze, cough and shortness of breath was observed in these infants. Observed associations were most marked for shortness of breath.
No independent association of symptoms with nitrous acid was seen. Health effects in children: One of the earliest studies to measure indoor nitrogen dioxide was conducted in the United Kingdom In the children who lived in gas-cooking homes, the prevalence of respiratory illness increased with increasing bedroom nitrogen dioxide level: No association of FEV0. Cross-sectional studies were conducted in the Netherlands, where there was concern over the combustion products produced by gas water heaters or geysers.
This supported earlier work in the Netherlands showing no association of indoor nitrogen dioxide level with respiratory symptoms Indoor nitrogen dioxide was measured on five occasions in three locations in the home and the frequency recorded of eight respiratory symptoms during the year of observation.
Respiratory symptoms were associated with the presence of a gas stove but not with any of the other sources of indoor nitrogen dioxide gas heaters or smoking in the home. The association of respiratory symptoms with a gas stove persisted even after adjustment for bedroom nitrogen dioxide, raising the possibility that the association with gas appliances was not explained by exposure to this pollutant.
Interestingly, both the presence of a gas stove and bedroom nitrogen dioxide level were non-significantly more strongly associated with respiratory symptoms in atopic children than in non-atopic children. In some parts of the world, children's exposure to gas combustion products may be determined or at least strongly influenced by their exposure to gas heaters at school.
This has been investigated in Australia. School levels of nitrogen dioxide were monitored during the winter, as were the personal levels of nitrogen dioxide in children who lived in homes with gas sources The winter average six-hourly mean nitrogen dioxide levels in classrooms with an unflued gas heating source ranged from There was some evidence of a dose—response relationship.
One of the most comprehensive assessments was conducted as part of the Six City study. The association of respiratory symptoms with indoor nitrogen dioxide level was examined in more than children , who were followed up for one year.
About half of the children lived in homes with a major source gas stove or kerosene heater. Household annual average levels were determined based on summer and winter measurements made in three household locations, and were At the end of follow-up, the annual cumulative incidence of any lower respiratory symptom shortness of breath, chronic wheeze, chronic cough, chronic phlegm or bronchitis was higher in those children living in homes with a source Household particulate matter PM 2.
The observed association of incidence of symptoms with both the presence of a gas stove and with increasing indoor nitrogen dioxide level persisted after adjustment for the indoor particle level. In this study, no consistent association of lung function with source or measured nitrogen dioxide was observed.
Further analyses were conducted later using regression calibration to include information from children who were not directly measured for nitrogen dioxide but who did have information on surrogate factors such as the presence of a gas appliance A detailed longitudinal study of the health effects of indoor and outdoor nitrogen dioxide was conducted in schoolchildren in Japan, a country in which the use of gas for cooking is almost universal and where some homes use unvented gas appliances for heating Indoor measurements of nitrogen dioxide were made in summer and winter mean of the two measurements in homes with vented and unvented appliances were There was no association of respiratory symptoms with exposure to gas heaters.
At baseline in girls but not boys , significant associations of indoor nitrogen dioxide with wheeze OR 1. However, over a three-year period there was no evidence that indoor nitrogen dioxide was associated with incidence of disease, although associations were seen with outdoor nitrogen dioxide level. Some studies have measured personal nitrogen dioxide rather than indoor levels. The extent with which personal nitrogen dioxide reflects exposure to indoor, compared to outdoor, nitrogen dioxide will vary depending on the time-activity patterns of the child and the frequency and duration of use of indoor sources.
Personal exposure to nitrogen dioxide was measured in children in Hong Kong SAR , where indoor sources are common. No association of exposure with symptoms was observed. However, personal exposure was strongly influenced by outdoor levels, with significant differences in personal exposure seen in children who wore samplers during a week of high ambient nitrogen dioxide Personal nitrogen dioxide exposure was measured in 3—4-year-old children in Quebec City, Canada during the winter months and a dose-dependent association of exposure with asthma was reported.
Only 6 of the children lived in a home with a gas stove mean personal exposure with gas stove The adjusted OR for case status with the highest level of exposure appears unrealistically high, with very wide confidence levels hour mean of The unmatched analysis OR was Personal nitrogen dioxide samplers were worn by Australian primary school children living in Canberra, a low pollution area They were worn from the end of the school day till the following morning, and if the child was taught in a classroom with a gas heater, classroom levels were also measured.
Average total personal exposure was low There was some evidence that this association was more apparent in children who were not mite-sensitized. One-week average personal exposure was measured in preschool children in Finland who attended one of eight day care centres.
A small proportion 9. Data from the same study were re-analysed using several methods of defining nitrogen dioxide exposure Overall, statistically significant associations of cough were seen only with personal exposure and in winter, although the direction of association with levels of nitrogen dioxide measured inside the day care centre, outside the day care centre and at a local fixed site was consistent with this observation.
Health effects in children with asthma: Several studies have examined nitrogen dioxide exposure in relation to symptoms of asthma in those with established disease.
All have observed increases in some symptoms, but some of the observed associations have not been consistent across the whole population under study.
In Adelaide, Australia, asthmatics wore lapel nitrogen dioxide monitors each day for six weeks while they were at home and kept a symptom diary In participants under the age of 14 years, there was an association of personal exposure level with symptoms of chest tightness OR 1. In adults, only one isolated association of one of the seven symptoms investigated was associated with nitrogen dioxide, and this was seen only after accounting for a one-day lag.
Personal exposure to nitrogen dioxide was measured in 45 asthmatic children over a day period by Delfino et al. The children, aged 9—18 years, were also subject to daily measurements of airway inflammation exhaled nitric oxide with a personal active sampling device. Positive associations were seen only in those who were taking anti-inflammatory medication, which may reflect the severity of the underlying disease.
In this population, there was a wide range of personal exposure 5. Daily lung function measurements were also made Personal nitrogen dioxide was associated with decrements in lung function, the change in FEV 1 as a percentage of predicted FEV 1 being 2.
Lung function associations were more clearly seen in those children who did not use a bronchodilator. These associations were robust to adjustment for personal PM 2. Three respiratory outcomes were considered: Associations of these outcomes with nitrogen dioxide were modified by atopic status and by season. Nitrogen dioxide levels in the highest quartile cut-off not given were associated with more than four days with symptoms compared to those exposed to lower levels, but this was only in children who had negative skin tests.
No association was seen in those who were skin-test-positive to at least one of 16 common indoor and outdoor aero-allergens. The overall difference in indoor nitrogen dioxide level in warm and cold months was relatively small 6.
The authors postulate that this may reflect increased susceptibility to infections during the colder months. However, as children spend more time indoors when it is cold, the association may have arisen because of the closer correlation of indoor measurements with personal measurements in the winter period. A total of inner-city children with asthma, predominantly African Americans, were studied over a six-month period in Baltimore, United States Although at baseline the average indoor nitrogen dioxide level was similar in the homes of asthmatic children and a control group of non-asthmatic children , there was evidence that indoor nitrogen dioxide was associated with symptoms in the asthmatic children.
Assessment of bedroom indoor nitrogen dioxide and indoor PM 2. There was a significantly increased risk of reporting symptoms with increasing nitrogen dioxide levels e. No association was observed for other outcomes such as medication use or use of health services. About two thirds of the children were atopic as assessed by skin tests, but in general the presence of atopy did not modify the associations observed. However, nocturnal symptoms were more strongly related to nitrogen dioxide levels in atopic children incidence rate ratio 1.
The association of symptoms in children with asthma with the use of gas appliances and indoor nitrogen dioxide level may be different in different housing conditions. In Connecticut and south-west Massachusetts in the United States, the reporting of wheeze and chest tightness in the month prior to indoor nitrogen dioxide sampling mean day average living room nitrogen dioxide Among these children in multi-family homes, exposure to gas stoves increased the likelihood of wheeze OR 2.
These multi-family homes were smaller, the implication being that main living room levels of nitrogen dioxide may better reflect the child's bedroom level. Children included in this study were the siblings of the infants recruited into the study reported by Belanger et al. One possible mechanism to explain the association of indoor nitrogen with asthma may be an increased susceptibility to severe or prolonged infection.
In England, children with asthma were followed up for almost a year, during which period they kept an asthma diary and measured their personal exposure over each seven-day period using Palmes tubes , When asthma exacerbations occurred, nasal aspirates were taken to confirm the presence of a viral infection. The geometric mean exposure to nitrogen dioxide at the time of infection was The risk of experiencing an episode of lowered peak expiratory flow after having experienced symptoms highly suggestive of infection increased in a dose-dependent fashion with increasing nitrogen dioxide levels at the time of the infection.
The increase in symptom score and the decrements in peak flow experienced during the laboratory-confirmed viral infection were larger in children who had higher exposures measured in the week prior to the start of the exacerbation. These observations that children with asthma have worse symptoms if exposed to higher levels of indoor nitrogen dioxide suggest that their removal from exposure should lead to amelioration of their symptoms.
However, few interventional studies have been reported. In recognition that classroom levels of nitrogen dioxide largely determined by the use of unflued gas heaters are an important source of exposure, an intervention study was conducted in Australia. Researchers assessed the effect of changing from unflued gas heaters in school classrooms to flued gas heaters or electric heaters Almost asthmatic children in 10 control schools, 4 schools that had changed to flued gas heaters and 4 schools that had changed to electric heaters were followed for a period of 12 weeks.
Following the intervention, the mean rate of symptoms of difficulty breathing during the day and at night, chest tightness and asthma attacks during the day was lower in children attending intervention schools. No change in lung function parameters was observed.
Six-hourly average classroom levels of nitrogen dioxide ranged from In further studies, of these children with asthma kept a symptom diary over a week period Home kitchen and classroom nitrogen dioxide levels were measured indoor daily range: Difficulty in breathing at night was associated with school adjusted relative rate 1. At the time of the study, mattress house dust mite levels were assessed; there was no evidence that the association of nitrogen dioxide with symptoms was modified by mattress allergen levels.
Another intervention study was conducted in New Zealand Parents of children with asthma, living in homes heated by an unflued gas heater or a plug-in electrical heater, were invited to alter their current heating system to either a heat pump, a wood pellet burner or a flued gas heater.
All eventually received their heater of choice, but they were randomized to receive them immediately treatment group or after one year control group. Improvements in subjective markers of health as reported by parents sleep disturbed by wheeze, dry cough at night, overall health symptoms reporting in diaries cough at night, wheeze at night and health service utilization visits to the doctor, visits to the pharmacist were seen in the treatment group but no change in objective markers such as peak flow variability or lung function tests were seen.
During the period of the study, the levels of nitrogen dioxide in the bedrooms and living rooms of the intervention group were 8. However, the intervention houses were also warmer 0. In the early s, Hasselblad et al.
This report was one of the earliest examples of the use of meta-analysis for synthesizing evidence from studies of environmental hazards.
It included published studies that had measured either indoor nitrogen dioxide or the use of a gas appliance as the exposure metric and combined the results from 11 studies, presented in 15 different publications from the Netherlands , , the United Kingdom , — and the United States , — Respiratory symptoms were any respiratory symptom, with some variation between studies but including wheeze, cough, coughs going to the chest, shortness of breath and bronchitis.
Exclusion of studies in which gas stoves were the proxy markers for exposure led to an increase in effect size OR 1. This analysis is of considerable importance, as it provided the basis for outdoor air quality guideline setting by WHO in and its conclusions have, to date, not been seriously challenged by any new evidence.
This value will avoid the most severe exposures. In comparison to the number of studies in children, there are relatively few studies that have reported associations of adult respiratory health with indoor nitrogen dioxide levels. Health effects in adults: Indoor nitrogen dioxide measurements were made in a subsample of households taking part in a longitudinal study in the United States mean hour average No association of respiratory illness in any member of the household including adult members with measured nitrogen dioxide level was observed A cohort of non-smoking women living in Vlagtwedde and Vlaardingen in the Netherlands was studied in Most 97 of the women had also had their FEV 1 measured and, in general, decrements in FEV 1 were associated with increases in indoor nitrogen dioxide levels, the largest estimates being seen for measurements in the bedroom mean deficit in FEV 1 2.
Although there was some evidence that increasing nitrogen dioxide level was associated with the decline in FEV 1 that had been recorded in these women over the previous 13 years, this association failed to reach conventional levels of significance.
Effect modification by atopy or asthma was not considered. In Hong Kong SAR, mothers of children taking part in a large study of respiratory health wore personal nitrogen dioxide badges for a hour period Personal nitrogen dioxide was higher in women if they cooked more frequently, but only among those who did not ventilate their kitchen by the use of an extractor fan.
In users of LPG or kerosene, the mean personal hour average exposure was There was no consistent association of personal nitrogen dioxide with frequency of cooking or presence of ventilation fans in the children living in these homes, probably reflecting their different time-activity patterns. Personal nitrogen dioxide was higher in women who cooked with LPG compared to those using piped gas. There was some evidence that personal exposure levels may be associated with chronic cough and allergic rhinitis.
The mean personal hour average exposure was Women who had recently given birth were recruited into a study in which health information was collected at baseline and the presence of respiratory symptoms regularly collected every two weeks for a year Indoor nitrogen dioxide measurements were made with passive samplers over a two-week period in the winter and this was repeated depending on whether gas or kerosene appliances were present.
Even though this was a large study involving non-smoking women, no association of nitrogen dioxide level with symptoms of wheeze, chest tightness, hoarseness or phlegm was seen when nitrogen dioxide was considered as a continuous variable. An association of symptoms with the use of kerosene heaters was reported and this may have been due to the sulfate emissions from these heaters. Indoor nitrogen dioxide levels were measured for one week in the homes of people with severe COPD living in north-eastern Scotland Half of the homes had at least one active smoker, and nitrogen dioxide levels were higher in homes with smokers median Kitchen, living room and bedroom nitrogen dioxide levels were measured for one week in the summer and one week in the winter in urban Pisa and rural Po Delta areas of Italy Mean kitchen levels of nitrogen dioxide were statistically different in the two regions An average personal exposure in adults was generated from time-activity patterns.
Exposure above the study median nitrogen dioxide index was associated with an increased risk of acute respiratory symptoms OR 1. Those who cook in the home and professional cooks are exposed to high levels of nitrogen dioxide as well as to other cooking-related pollutants. There is no evidence from large-scale epidemiological studies that have measured indoor nitrogen dioxide levels that respiratory health is worse in those who regularly use unvented gas appliances for cooking.
Confounding by other cooking-related pollutants cannot be ruled out. In setting guidelines for indoor air quality, there is clearly a need for direct measurements of nitrogen dioxide levels, and for these levels to be associated with some health impairment. In the indoor setting, however, where the source of indoor nitrogen dioxide may, in the main, be from indoor gas appliances, the presence of the appliance itself may act as a proxy marker of exposure.
Of particular concern is that the use of some appliances, particularly gas cookers which are unvented is associated with short-lived peaks of exposure that are not captured or measured by most of the monitoring techniques used in epidemiological studies. Under these circumstances, association of a health effect with the presence and use of the gas appliance may provide stronger evidence of health effects of indoor nitrogen dioxide than measurements of the gas itself.
However, there are three major pitfalls with this approach. This may explain the heterogeneity in the results of studies. Third, and related to the previous point, the group selected for comparison should ideally comprise a group that uses electricity. This may be difficult in countries where gas is used almost universally — for example, until more recently in Hong Kong SAR and Italy.
There are many more studies on the association of health with the presence of gas appliances than with measured nitrogen dioxide and they are of varying quality. While cross-sectional studies are of interest in making a causal inference, greater weight would naturally be placed on those that are longitudinal in design. Further, in older children and adults, objective markers of disease such as lung function may be used and these measurements, in well-designed studies, could be argued to provide better evidence for associations than those that are based on self-reported symptoms.
However, respiratory disease may occur in the absence of measurable change in lung function parameters. The acute effects of direct exposure to gas combustion have been studied in people's homes. An early pilot study that used this approach reported change in FVC in asthmatic and non-asthmatic women in whom continuous measurements of nitrogen dioxide were made during cooking at home over a five-day period Spirometric measurements were made before, during and after each cooking period.
This was not seen in the non-asthmatic women, but it should be noted that the peak nitrogen dioxide levels for the non-asthmatic group were not as high no reason was given for this. In another study, 16 adult non-smoking women with asthma had their peak flow measured before and after cooking with gas in their own homes.
Cross-sectional studies conducted more than 25 years ago suggested that the use of gas cooking was associated with increased hospital admissions for respiratory disease in preschool children in the United States and more respiratory symptoms in schoolchildren in England and the United States — Participants in the United Kingdom study were followed for about five years and there was some evidence that the association became less apparent as the children became older Other cross-sectional studies conducted at a similar time did not observe these associations , , and a longitudinal study in which children were studied for one year to identify episodes of respiratory illness also found no association Many, but not all, of these early studies made attempts to adjust for potential confounding by social class, parental smoking and other household factors, recognizing that the use of gas appliances, in some communities at least, was strongly related to lower socioeconomic status and increased rates of parental smoking Greater bronchodilator responses were observed in children exposed to tobacco smoke than in those who were not exposed, but no such difference was seen in children exposed to gas cooking appliances, even though an association of symptoms with the use of gas had been observed.
In the past, unvented gas water heaters were relatively common indoor gas appliances in the Netherlands, and researchers have examined their effect on children's health. Lung function was measured by spirometry and a forced oscillation technique in primary school children There was no clear, consistent association of spirometric indices or of measurements of impedance with the use of these appliances, although the small observed differences were in the expected direction and were greater for measurements of resistance and impedance in girls.
Large-scale cross-sectional studies have been conducted more recently. The lifetime prevalence of other symptoms was not increased. White blood cell counts were increased in children in homes with gas cookers, particularly in those likely to be exposed to high levels of gas-cooking-derived pollutants those in homes with no extraction fans or smaller homes, and children who spent more time indoors.
There was a suggestion that this latter association may be stronger for bottled gas than for the town gas that was in use at the time. In 4—5-year-old Australian children, the use of a natural gas stove was associated with an increased risk of wheeze, asthma and colds In the Third National Health and Nutrition Examination Survey, use of a gas stove for cooking or for heating was associated with an increased risk OR 1.
Effect modification by allergic predisposition, as shown by total IgE levels, on the association of lung function with exposure to gas has been observed in a cross-sectional study of adolescents. This association was observed mainly in girls with total IgE above Effect modification by total IgE level persisted even if children with positive skin tests were excluded.
This study suggests a dose-dependent association of exposure to gas cooking with airway function that is modified by both atopy and gender in this age group. However, confounding by exposure to cooking fumes or other pollutants from gas combustion cannot be ruled out.
However, this association was only seen in girls who did not take asthma medication and was not seen in boys. The association of respiratory symptoms with gas for cooking may be modified by levels of outdoor nitrogen dioxide.
Children living in two contrasting areas were examined Using a case-control design, the association of severe asthma children whose parents reported that they suffered either 12 or more wheezing attacks in the past 12 months or an attack of wheeze over the same period that limited speech to only one or two words at a time between breaths with use of gas for cooking was examined Controls were children with no history of asthma or wheezing at any age.
There was no evidence that the use of gas for cooking differed between cases and controls adjusted OR 0. A longitudinal study design has been adopted in some studies to examine the health effects of exposure to gas appliances in infancy. Although the proportion of children with a respiratory illness and with an admission to hospital for respiratory illness was higher in homes with gas cooking, the difference was not significant.
The association of exposure to gas appliances in infancy to later respiratory health was examined in Australia, where gas heaters are the main source of indoor combustion products. As part of the Tasmanian Infant Health Survey, the type of heating appliance in use in infancy was recorded and, at the age of seven years, information on respiratory symptoms was collected Only a small proportion of the children lived in homes with a gas heater most likely to have been fuelled by LPG but this small group had a substantially increased risk of asthma in later life 1.
In the same publication, the authors presented results from an extended analysis involving more than children, in which they noted a cross-sectional association of recent wheeze OR 1. Another publication using data from the same children looked at the association of gas use in infancy with lung function Those who had lived in a home with either a gas heater or a gas cooker in infancy were more likely to be sensitized to house dust mites and had a lower FEV 1.
In the children included in this analysis, the association of asthma with the use of gas was below conventional levels of significance. However, airway obstruction was more strongly associated with current gas cooking in children sensitized to house dust mites than in those not sensitized. The long-term health effects of exposure to gas appliances was also examined in a United Kingdom study that measured prevalence of wheeze in teenagers in relation to exposure to gas cookers as a child Almost children provided information on symptoms at ages 7—8 and 15—17 years and, in addition, at the age of 16—18 years reported their use of gas appliances for cooking or heating in their current home and in their home when they were a child.
Childhood wheezing was associated with childhood exposure to any gas appliance and with childhood exposure to a gas hob OR 1. However, childhood exposure to gas appliances was not associated with wheeze that persisted into the teenage years. Wheeze in adolescence was not associated with current teenage exposure and, surprisingly, persistent wheeze was less frequent in those exposed to gas in the teenage years. The authors argued that this latter observation might be explained by selective avoidance.
A similar age group was studied as part of a longitudinal study in southern California Participants aged 9—16 years were recruited and followed for five years or until graduation.
Over the five-year period, there was no evidence that the presence of these appliances was associated with the incidence of physician-diagnosed asthma in children with or without wheeze at baseline. Longitudinal studies have been used to examine whether exposure to gas appliances has a deleterious effect on lung growth in children.
In Arizona, United States, a four-year study was conducted to determine whether living in a home where gas was used for cooking was associated with poor lung growth in children aged eight years at baseline. Despite strong cross-sectional associations of the use of gas for cooking with symptoms of wheeze, cough and sputum production at baseline, there was no evidence that exposed children had lower rates of lung growth than unexposed children First reports from the study suggested that exposure to gas stoves was associated with reduced lung function in children Later work suggested that a reduction of 0.
After further examination, analyses based on children aged between six and ten years who had between two and five annual measurements of lung function showed no effect of the use of a gas stove on pulmonary function level at the end of the study As part of the meta-analysis conducted by Hasselblad et al. If we hypothesize that the health effects of combustion products such as nitrogen dioxide from unvented gas appliances depend on repeated high exposures, those that actually use the appliances and are therefore exposed to these peaks would be expected to be at greatest risk.
In most communities, cooking remains a task largely performed by women and particularly by young and middle-aged women with large families. This being so, we might expect women to be at particular risk. However, one of the first studies examining the association of the use of gas with respiratory health suggested the opposite.
In a community-based representative sample of almost adults in Maryland, United States, men living in homes with a gas cooker had more chronic cough and wheeze with breathlessness than those living in homes with electric cookers.
No association was seen in women. The authors hypothesized that women have, over thousands of years, been exposed to pollutants generated by cooking and heating and have an evolutionary advantage over men in being resistant to the health effects of exposure to fumes from cooking and cooking appliances , A small case-control study was conducted shortly afterwards.
The type of cooker that was used by non-smokers with FEV 1 in the highest quartile of the distribution was compared with that used by non-smoking women with FEV 1 in the lowest quartile Exposure to gas appliances was non-significantly higher in those with low lung function Effect modification by atopy or frequency of use was not examined. Large-scale cross-sectional studies conducted more recently in the United States suggest little association of symptoms with use of gas in either men or women.
There was no association of current gas stove use with symptoms of phlegm, wheeze or dyspnoea, although an association with chronic cough was seen OR 1. In fact, those who had a gas stove appeared to have better lung function than those who did not.
These analyses were extensively adjusted for other household and sociodemographic factors. Effect modification by gender and by atopy as measured by skin tests was tested and was not observed. Nevertheless, an analysis of data collected as part of the ECRHS multicentre study presented evidence that respiratory symptoms suggestive of asthma, and lung function changes suggestive of airway obstruction, may be associated with the use of gas cooking in some communities , A strong cross-sectional association of respiratory symptoms with the use of gas for cooking was seen in women, but not men, living in three towns in England.
However, when the same statistical approach was extended to include these centres, considerable heterogeneity was observed between centres with the strongest effects being seen in the United Kingdom centres. In this early study no information on frequency of use, use of natural ventilation, type of gas used and maintenance of appliances was collected.
Researchers in the Netherlands looked for effect modification by atopy on the association of gas cooking with bronchial reactivity. The protocol adopted for the study was that of the ECRHS but the age range studied was larger 20—70 years. Atopy was defined by the presence of specific IgE to common aero-allergens and measured bronchial reactivity to methacholine.
There was no evidence that atopics had greater bronchial reactivity if they used gas for cooking, but the associations were much stronger in both men and women who had high total IgE compared to those with low total IgE. None of these authors considered whether total IgE was higher in those who cooked with gas and was a surrogate marker for greater exposure to gas. Older adults may not use their gas cooking appliances as frequently as those living with small children. In a questionnaire survey of men and women aged 65 years or older in Bristol, United Kingdom, the presence of a gas hob or gas oven was associated with a small, non-significant risk of respiratory symptoms suggestive of COPD Many people in this age group will no longer be preparing meals for their families and no information was collected on the frequency of use of gas hobs and ovens.
Associations may have been weak owing to infrequent cooking in this age group. Many of the remaining cross-sectional studies in adults have been restricted to women. In Polish women over 65 years of age, chronic cough, chronic phlegm and shortness of breath on exertion were more common in those who cooked with gas for more than three hours a day compared to those who cooked with gas less frequently In a study of women in Singapore , there was a non-significant increased risk of respiratory symptoms among non-smoking women who cooked frequently and a significantly reduced adjusted FEV 1 noted in those who described themselves as housewives and who cooked frequently 0—2 times a week 1.
Stir frying with spices and chillies is a common method of cooking, and regular cooking is most likely to be associated with greater exposure to oil mists and frying fumes that may themselves cause respiratory symptoms. This could reflect poor ventilation and greater exposure to the products of gas combustion, but could also reflect greater exposure to pollutants created by cooking. Nearly half of the asthmatics studied cooked with gas but they had only a non-significant increased prevalence of symptoms of wheeze and dyspnoea and had the same lung function FEV 1 , FVC or FEF 25—75 as those who cooked with electricity.
In another report, the same research group followed asthmatics living in California over an month period. Those who cooked with gas had similar health service utilization rates hospital admissions and emergency department visits as those who cooked with electricity. There was no evidence that the reporting of use of a gas stove at baseline or changing the use of that gas stove over the period of the follow-up was associated with asthma severity or with SF or asthma-specific quality of life scores, even though associations with exposure to ETS were observed Longitudinal studies over several years of follow-up to examine the chronic respiratory health effects of gas cooking in adults are less common than cross-sectional studies, but some have been published.
About half of the families used electricity to cook and the rest used gas, but overall the rates of respiratory illness in mothers and children were lower in families with gas cookers than in families with electric cookers. The longest follow-up has been of residents of households in Chesterfield, England, that were included in a housing survey in The presence of a gas cooker in the home at the time of the survey was not associated with overall mortality in children or adults and was negatively associated with death ascribed to COPD RR 0.
This result is unsurprising, as positive results would have implied a very strong association of gas cooking at one point early in life with development of severe respiratory disease many years later, without adjustment for smoking. The largest longitudinal study with the most comprehensive analysis to examine respiratory outcomes in adults, based on exposures in earlier life, was from the birth cohort in the United Kingdom In a sample of adults enriched with people who had a history of wheezing in earlier assessments, information on the fuel currently used for cooking and the fuel used for cooking when the participant was 11 years old was collected at age 35 years.
Of those who first reported symptoms indicative of asthma at the age of 7 years, those who reported using gas for cooking at age 35 years were more likely to report current wheeze than those who currently used electricity for cooking OR 1.
This increased risk was greater in women OR 1. Cross-sectional analyses of the people with asthma or wheeze in the previous year showed little evidence that the current use of gas for cooking was associated with current asthma severity as measured by number of attacks of asthma or the reporting of sleep disturbed by wheezing in the previous 12 months.
This latter association was not examined in men and women separately. A longitudinal design was used to assess acute health effects of exposure to gas appliances in a panel study of asthmatics living in Denver, United States Participants recorded symptoms, medication use and their use of indoor gas appliances.
In developing countries, many people cook with either biomass or with gas usually LPG. Use of biomass is associated with a range of health effects, which were reviewed in Solid fuel use was shown to be associated with acute lower respiratory tract infection, COPD, asthma, cataracts, tuberculosis and lung cancer. Association of nitrogen dioxide with disease in these settings is likely to be confounded by the high particulate counts.
Those who used kerosene had a significantly increased risk of IgE sensitization to aero-allergens, eczema and rhinitis compared to those who did not. Those who used gas had some increased risk and those who used electricity had an increased risk for eczema only. The authors argued that the increased risk of allergic outcomes in those using modern fuels producing nitrogen dioxide was unlikely to be explained by factors associated with socioeconomic status, as they had adjusted for this family occupation, household crowding.
Some of the variation in the associations of gas cooking with symptoms may be explained by the type of gas used. In areas where there is no piped gas, LPG is often used. In a study of more than 25 children in the United Kingdom, there was no association of gas used for cooking or heating with wheeze symptoms Children who lived in homes that used bottled gas which in this study also included paraffin were at an increased risk of wheeze compared to those using electricity for heating OR for speech-limiting wheeze 1.
One of the few studies in developed countries to examine the association of bottled gas compared to mains gas on respiratory health in adults was conducted in Italy, where cooking with gas is almost universal. The type of gas used for cooking was closely associated with the type of heating in the home, and exposure status was defined by both heating and cooking appliances. The lowest prevalence of symptoms was in those with natural gas central heating and gas cooking.
Dyspnoea was more common in men and women who used bottled gas for cooking compared to those who used natural gas. No effect modification by atopy was examined or reported. Bottled gas appliances were not subject to the mandatory regulation and official inspection imposed on natural gas appliances. High concentrations of nitrogen dioxide are observed in indoor ice arenas that use resurfacing machines powered by combustion engines, and studies have been conducted to assess the effect of exposure to nitrogen dioxide in this setting.
A review of studies in which measurements were made of both nitrogen dioxide and carbon monoxide in indoor ice arenas was published in Exposure to nitrogen dioxide in this setting is accompanied by exposure not only to carbon monoxide and particles but also to cold air, and cross-sectional studies suggesting a high prevalence of respiratory symptoms in ice hockey players and figure skaters may reflect a response to cold air. This interpretation is supported by evidence that the prevalence of asthma is higher in those who participate in outdoor winter sports such as cross-country skiing To overcome this problem, one study in Sweden compared respiratory symptoms in children who played ice hockey in ice arenas with propane-fuelled and electric resurfacing machines Some children aged between 10 and 16 years who had played ice hockey in the previous three years and had trained in one of 15 indoor ice arenas were identified.
Symptom prevalence wheezing in the last 12 months, exercise-induced wheeze, physician-diagnosed asthma or current rhinitis was non-significantly higher in children who trained in arenas with an electric resurfacing unit rather than a propane unit. The authors then looked at children attending the propane arenas only.
All symptoms were more common in those attending high nitrogen dioxide propane arenas and this reached statistical significance for those who had ever had symptoms of rhinitis OR 1.
Chronic health effects of exposure were also examined in Finland Im engeren Sinne ist damit nur die sogenannte Präadipositas gemeint, im Gegensatz zum schweren Übergewicht , der Fettleibigkeit oder Adipositas. Das medizinische Fachgebiet, das sich mit dem Übergewicht beschäftigt, ist die Bariatrie.
Übergewicht kann auf verschiedene Arten definiert werden, siehe dazu Berechnungsformeln. Übergewicht tritt gehäuft in industrialisierten Ländern auf, wo nur noch wenige Menschen harte körperliche Arbeit verrichten und Nahrung im Überfluss vorhanden ist.
In den Industriestaaten ist Übergewicht weit verbreitet und wird dabei aufgrund des modernen Schlankheitsideals als unästhetisch empfunden. Die höchsten Zuwachsraten Übergewichtiger an der Gesamtbevölkerung, insbesondere jugendlicher Übergewichtiger in der Altersgruppe, werden jedoch nicht in den gewachsenen Industrienationen erreicht, sondern in den Schwellenländern. Demzufolge ist zu vermuten, dass die globale Übergewichtsexplosion erst noch der nächsten Generation vorbehalten ist.
Der Anteil der Übergewichtigen nimmt stetig mit dem Alter zu. Bei den Männern ist Übergewicht in der Altersgruppe der bis Jährigen am meisten verbreitet, bei den Frauen in der Altersgruppe der bis Jährigen.
Mit steigender Bildung sinkt der Anteil der Übergewichtigen. Das trifft besonders auf Frauen zu. Perzentils und Adipositas als das Überschreiten des Perzentils einer Referenzpopulation von — definiert. Legt man die Referenzdaten von — zugrunde, dann ist insbesondere eine markante Zunahme ab Schuleintritt im Alter von 6—7 Jahren festzustellen. Es gibt weiterhin keine geschlechtsspezifischen Unterschiede; eine höhere Wahrscheinlichkeit übergewichtig zu sein, besteht bei einem niedrigen sozialen Status Arbeitslosigkeit, Arbeiter und Migranten und bei übergewichtigen Müttern.
April veröffentlicht wurden. Es gibt keine einheitlichen Erhebungsmethoden, die Daten sind nach eigenen Angaben der Zusammenstellung nicht altersstandardisiert und die Quelle der Daten ist nicht angegeben. So werden hier unter anderem Umfragedaten mit Messdaten vermischt sowie die Gruppe der bis Jährigen weggelassen, die einen wesentlich geringeren Anteil an Übergewichtigen aufweist. In einer veröffentlichten Längsschnittstudie über 5 Jahre mit Menschen inklusive Paaren im Alter zwischen 12 und 28 Jahren zeigte sich, dass neu verheiratete Frauen und Männer deutlich mehr Gewicht zulegten als Paare, die zusammenlebten, aber nicht heirateten.
Am geringsten waren die Gewichtszunahmen bei Singles. Verstärkt werden diese Ursachen durch Werbung für energiereiche Nahrungs- und Genussmittel: Es wirken immer genetische und andere Faktoren lebenslang gleichzeitig, sie stellen keinesfalls alternative Wirkweisen dar.
Die untersuchten Zwillinge ähnelten in ihren Gewichtsmerkmalen eher ihren leiblichen Eltern als ihren Adoptiveltern. Andere Forschungsergebnisse deuten darauf hin, dass genetische Defekte zu einer verminderten Ausschüttung des Hormons Leptin führen können, welches eine wichtige Rolle bei der Regulation des Hungergefühls spielt.
Entscheidend und einzige beeinflussbare Faktoren sind die Lebensverhältnisse, das persönliche Essverhalten und die Bewegungsgewohnheiten. Ein Einfluss der Lebensverhältnisse auf das Auftreten von Adipositas kann in jedem Fall gefunden werden. Nach einer Studie  des Deutschen Instituts für Ernährungsforschung , die an Mäusen durchgeführt wurde, besteht ein Zusammenhang zwischen dem Konsum von Fruchtzucker Fructose und Übergewicht, der nicht auf einer vermehrten Kalorienaufnahme beruht, sondern auf einer Beeinflussung des Fett- und Kohlenhydratstoffwechsels.
In der Tat konnte auch in einer Untersuchung an Menschen gezeigt werden, dass Fructose vom Körper sehr viel schneller in Körperfett umgewandelt wird als Traubenzucker Glucose. Dass Nachtarbeit und Schlafmangel zu Übergewicht führen kann, wird zumindest teilweise auf eine Störung des Insulinhaushalts zurückgeführt: Inzwischen gibt es deutliche Belege, dass bereits Präadipositas ein Gesundheitsrisiko darstellt.
Übergewichtige eine höhere Lebenserwartung als sog. Eine häufig zitierte Metaanalyse kam zu dem Schluss, dass erst ab einem BMI von 35 eine erhöhte Sterblichkeit gegenüber dem Normalgewicht bestehe. Dem widerspricht nun aber die bislang umfassendste, veröffentlichte Studienauswertung, der zufolge bereits bei einem BMI oberhalb 25 die Risiken für koronare Herzkrankheit, Schlaganfall, Atemwegserkrankungen und Krebs allesamt erhöht sind und mit jedem weiteren Kilo weiter ansteigen.
Das "Adipositas-Paradoxon" existiere nicht; die populäre These vom "gesunden Übergewicht" wird damit als widerlegt angesehen; sie beruhe auf verzerrten Daten, bei denen z. So hat die International Diabetes Federation im Jahr einen erhöhten Bauchumfang als eines der Kriterien für die Diagnostizierung des Metabolischen Syndroms festgelegt. Folgen von Übergewicht können sein: Übergewicht kann nicht nur psychologisch verursacht sein, sondern kann auch psychosoziale Folgeerkrankungen nach sich ziehen: Es ist ein Teufelskreis: