It is not just what you eat, what you breathe might also cause obesity. Long-term exposure to high levels of air pollution is strongly co-related to obesity, found a study of over 3,000 schoolchildren from Delhi, Kottayam, and Mysuru. This was a surprise finding by the researchers trying to understand the impact of air pollution on the lung health of children in Delhi.
The study found 39.8% of the children in Delhi were obese or overweight as compared to 16.4% in Kottayam and Mysuru (which have better air quality). The researchers found the children, who are obese, or overweight, are at a 79% higher risk of developing asthma across all three cities as compared to their healthy weight counterparts. Obese children in Delhi were at a 38% higher risk of developing asthma than their counterparts in Kottayam and Mysuru.
"The burden of asthma is also much higher than anticipated. Usually, we say that the prevalence is between 8 to 12%. Some studies have shown a prevalence of up to 20%. But our study shows a prevalence of nearly 40% among boys," said Arvind Kumar, founder of Lung Care Foundation, which conducted the study in association with Pulmocare Research and Education.
"What this essentially means is that pollution not only leads to a higher burden of asthma, but it also correlated to increased obesity which then leads to asthma. The correlation between air pollution and obesity was a surprise finding for us. The question on BMI (body mass index) was included along with all other demographic parameters, but when we looked at the data, we were shocked. That is when we went back to the medical literature and found that a few recent studies have called pollution an obesogen."
The study did not specifically look at the mechanism by which pollution leads to obesity.
Kumar said the toxins in the air either act on the fatty cells making them resistant to insulin or they affect endocrine axis leading to binge eating. "Larger studies are needed to conclusively prove the link."
The study also found a very high incidence of asthma in children in Delhi.
The prevalence of asthma confirmed through on-the-spot spirometry tests, which determine the amount of air a person breathes out, was found to be 29.3% in Delhi children as compared to 22.6% in those from Kottayam and Mysuru.
This was despite a higher prevalence of predisposing factors such as a history of smoking and asthma in the family. Only 29.8% of the children in Delhi had a history of asthma as compared to 33.7% in Kottayam and Mysuru. In Delhi, 13.9% of the children reported smokers in their families as compared to 18.8% in Kottayam and Mysuru, according to the study.
"What this shows is pollution has a higher impact on asthma than known risk factors such as the history of the illness in the family or a smoker in the family. We found that boys were twice as likely to have asthma as girls across the cities. What was worse was most of the children were not aware of their asthma and hardly any of them were on proper treatment. One of the reasons for higher diagnosis in the control cities could be that there were more cases of asthma in the family leading to discussions about the disease and health-seeking behaviour. Conversely, with many allergic symptoms already reported in a high proportion of children in Delhi most people think it is part of life," said Kumar.
Only 12% of the Delhi children, who were found to be asthmatics, had been diagnosed and 3% were under treatment. In comparison, 27% in Kottayam and Mysuru had been diagnosed and 8% were under treatment.
"This study has shown that around 85% of adolescent children who were found to have asthma in Delhi, did not know that they had asthma, and less than 3% of them were receiving appropriate treatment. Clearly, we need to create more awareness about asthma among parents and teachers, so that under diagnosis and under treatment of asthma can be significantly overcome," said Anurag Agarwal, one of the authors of the study paper and director of the Institute of Genomics and Integrative Biology, in a statement.
The researchers reported higher allergic symptoms in Delhi children. This included sneezing in 52.8% of children in Delhi over the last 12 months as compared to 39.3% in the control cities.