Prevalence of pre-clinical autoimmunity in the normal adult population residing in a metropolitan city of India: A cross-sectional study

OBJECTIVE: A steep rise in the incidence of autoimmune diseases over the decades has been observed, which is simply not explainable with population-level genetic changes, indicating thereby that environmental factors play an important role in their causation. Then again, how air pollution affects the immune system is still not completely elucidated. This study intends to check the presence of autoantibodies and inflammatory markers in normal adults residing for more than 10 years in a highly polluted region. METHODS: In this observational cross-sectional study design, 1,500 subjects residing in Delhi, India, for more than 10 years were screened, of whom 500 were recruited for the study. Distance from the main road to an individual’s house was calculated, which was taken as a proxy for traffic pollution exposure. These subjects were analyzed for autoantibodies and inflammatory markers. RESULTS: The mean age of our cohort was 31.0±8.3 years. Autoantibody positivity was observed in 18% of the subjects, whereas inflammatory markers were elevated in 68% of the subjects. Subjects residing within 200 m of the main road had a higher prevalence of autoantibodies antinuclear antibody (12.5% vs 6.5% p=0.03) and rheumatoid factor (9.6% vs 4.5% p=0.02) than the subjects residing at or more than 250 m away from the main road. CONCLUSION: A total of 18% of normal subjects had autoantibody positivity. The odds of developing antinuclear antibodies were twice higher in subjects who resided within 200 m of the main road where the exposure to pollution was higher.