Journal Club - Long term exposure to air pollution linked to diabetes in Indian population

Air pollution is a critical and manageable risk factor for diabetes and hence there is a need for awareness about air pollution in the society and at the government level, says a recent study in the Journal of the Association of Physicians of India. The study found that long- term air pollution is associated with impaired glucose tolerance (IGT), impaired fasting glucose (IFG), and diabetes prevalence.

Exposure to air pollution has been shown to adversely impact health through a number of biological pathways and is also tied to glucose metabolism. Only a few studies have investigated the associations between air pollution and fasting blood sugar and HbA1C levels but no such study was conducted in the Indian population. 

To address the knowledge gap described above, Monika Gupta FROM Sardar Patel Medical College, Bikaner, and colleagues aimed to evaluate the associations between air- borne fine particulate matter (PM10, PM2.5), nitrogen dioxide, and glucose metabolism in a tertiary care center in northwestern Rajasthan.

For this purpose, the researchers performed a cross-sectional analysis of 3457 participants between 30 to 70 years of age group from five different urban and rural areas of the Bikaner district. The ambient air quality standard method by respiratory dust sampler was used to estimate air pollution concentration of multiple air pollutants (PM10, PM2.5, and Nitrogen dioxide). 

Diabetes was defined based on medication prescription, self-reported diagnosis, HbA1C, and oral glucose tolerance test. Potential confounders including smoking habits, socioeconomic status, Body Mass Index (BMI), physical activity, and alcohol consumption were adjusted using a logistic regression method. 

Based on the study, the researchers revealed the following findings:

 After adjustment for potential confounders, air pollutants PM10, Nitrogen Dioxide (NO 2 ), except PM2.5 was associated with diabetes prevalence.

The prevalence of diabetes was 8.93% and the mean HbA1C was 8.67±1.16, whereas the concentration of PM10 was 156.12 mcg/m3, NO2 was 5.43 mcg/m3 and PM2.5 was 25.36 mcg/m3.

 The prevalence of impaired fasting glucose, impaired glucose tolerance, and diabetes increases with an increased concentration of air pollutants.

 By applying Pearson's co-relation coefficient for air pollutants i.e the 'r' value of PM10 was 0.163, p value < 0.001, for PM2.5 'r' value was 0.001 and p value 0.965,

for NO2 'r' value was 0.149 and p value was 0.001 respectively. By applying step-wise logistic regression analysis, air pollutants PM10 (Odd Ratio 0.002) and by adding the duration of exposure to air pollutants (Odd ratio 0.003) by adding PM2.5 air pollutant (odds ratio 0.028) and by adding NO2 (odds ratio 0.140).

The authors wrote that "We found that long-term air pollution exposure was associated with impaired fasting glucose, impaired glucose tolerance, and prevalence of diabetes mellitus (DM)," wrote the authors.

THE RESEARCHERS CONCLUDED THAT "This study can be used as good evidence that air pollution is an important and manageable risk factor for diabetes hence there is a much need for awareness about air pollution in the society and at the government level," they concluded.