Association between short-term exposure to fine particulate matter and daily emergency room visits at a cardiovascular hospital in Dhaka, Bangladesh.

BACKGROUND: It has been suggested that exposure to fine particulate matter (PM2.5) adversely affects cardiovascular health. However, the effect modifications by individual characteristics and season have been less studied in developing countries where PM2.5 levels are high. OBJECTIVES: To estimate the risks of cardiovascular emergency room visits in relation to daily concentrations of PM2.5 and to assess how these associations can be modified by age, sex, and nutritional status of patients and by season. METHODS: The analytic sample was 6774 adults who visited the emergency room at a cardiovascular disease (CVD) hospital in Dhaka throughout one year (n = 364 days). A time-stratified case-crossover design with conditional Poisson regression analysis was used to estimate the relative risks (RRs) and 95% confidence intervals (CIs) of visits while adjusting for temperature. Stratification was performed by gender, age (<65 and ≥65 years), BMI (underweight, normal weight, overweight), and season (dry summer: February to April; wet summer: May to October; dry winter: November to January). RESULTS: The mean concentration of PM2.5 was 86.1 µg/m3. An IQR increase (103 µg/m3) in PM2.5 at lag 3 was significantly associated with a 12% (RR: 1.12; 95% CI: 1.01-1.23) increase in CVD emergency room visits. No evidence of association was found for the other lags. Underweight and overweight patients showed evidence of increased risk at lag 2 (RR: 1.31; 95% CI: 1.02-1.67) and lag 4 (RR: 1.20; 95% CI: 1.04-1.39), respectively. CONCLUSION: Increases in the daily concentrations of PM2.5 may lead to more cardiovascular emergency room visits in Dhaka, Bangladesh. Response times from ambient exposure to CVD emergency visits may differ by season and the nutritional status of susceptible individuals, necessitating further research.