Exposure to traffic-related air pollutants is associated with a rapid increase in systemic inflammation in patients with diabetes, report Indian researchers.
The team found that among patients attending a diabetes clinic in the city of Pune in India, high concentrations of serum C-reactive protein (CRP) were associated with increased ambient levels of sulfur dioxide (SO2) and nitrogen oxide (NO).
The study was based on data on CRP levels that the researchers had previously collected for diabetic patients as part of the Wellcome Trust Genetic Study, and the patients' exposure to different ambient air pollutants were assessed using data from the National Air Quality Monitoring Program that has been in place since 2004.
As reported in Diabetes Care, 57% percent of 1392 patients had CRP concentrations in the high coronary risk zone (>3 mg/L) and 19% had abnormally raised CRP levels (>10 mg/L).
Each standard deviation increment in city-wide SO2 on the day of blood sample collection was associated with a significant 9.34% increase in CRP concentration and in the 7 days before a clinic visit, with 8.67% to 12.42% increases.
For NO, CRP increased by 7.8% to 11.6% up to 7 days before the visit and by an average of 12.8% 7 days before attending, report Chittaranjan Yajnik, from the King Edward Memorial Hospital Research Center in Pune, and colleagues.
The most significant associations between SO2 and CRP levels were observed among patients with a diabetes duration of less than 7 years and in patients who were not treated with statin or thiazolidinedione therapy.
"Higher inflammatory response in newly diagnosed diabetic patients could be attributed to their younger age and therefore possibly more exposure to outdoor air pollution, and because many were not yet started on medication that lowers inflammation," says the team.
Given existing evidence that CRP levels are associated with the development and complications of the metabolic syndrome, the findings may have implications for the risk for cardiovascular disease in city-dwelling Indian diabetic patients.
In addition, the results "should promote studies on the effect of air pollution on the risk of noncommunicable disease in India," writes the team.
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