Brick Kiln Pollution and Seasonal Blood Pressure Variation in Bangladesh

In Bangladesh, air pollution levels are higher in the dry winter months than in the rainy summer months. Much of this fluctuation can be attributed to brick kilns, which emit pollutants only in the winter “brick season.” This analysis examines whether seasonal variation in air pollution might affect blood pressure and prevalence of hypertension in Bangladesh.
Using longitudinal data from a study of 2,242 adults in Mirzapur, Bangladesh, we analyzed differences in blood pressure between winter 2018 and summer 2019. Decreases in systolic and diastolic blood pressure in the summer compared to the winter were experienced by 73% and 76% of participants. The between-season differences for mean systolic and diastolic blood pressure were 8.49mmHg (p<.0001) and 6.40mmHg (p<.0001), respectively. The prevalence of hypertension was 43% in the brick season and 22% in the non-brick season.
We conducted a literature review of the association between temperature and blood pressure and used a summary effect estimate from this review to estimate the extent to which temperature might explain the seasonal patterns we observed. Using a mean effect estimate derived from 28 studies (systolic=0.29mmHg/-1°C, diastolic=0.13mmHg/-1°C), we calculated that the observed seasonal differences in systolic and diastolic blood pressure exceeded what could be expected due to temperature variation alone by 6.32mmHg and 5.32mmHg, respectively.
We concluded that seasonal spikes in air pollution likely contribute to increases in blood pressure and hypertension prevalence. Given recent increases in the prevalence of cardiovascular disease, we recommend policy and public health measures be taken to reduce exposure to air pollution in Bangladesh.