Long-term exposure to PM2.5 and mortality among Japanese community-dwelling adults

Abstract Background Long-term exposure to PM2.5 (particulate matter with a diameter of 2.5 μm or smaller) is a risk factor for mortality and cardiovascular disease including stroke. However, there was limited evidence for the association between PM2.5 exposure and stroke in Asia where the major cardiovascular disease is stroke. Additionally, the causal association between PM2.5 and respiratory disease is still unresolved. The aim of this study was to investigate the association between long-term exposure to PM2.5 and all-cause, cardiovascular, and respiratory disease mortality in a Japanese community-based prospective cohort. Methods This study included 46,974 participants (19,707 men; 27,267 women) from the second cohort of the Ibaraki Prefectural Health Study. The participants were followed up from baseline survey (in 2009) to 31 December 2019. We confirmed underlying causes by death certificates. Using the PM2.5 concentrations estimated by the inverse distance weighting methods based on ambient air monitoring data, administrative area level concentrations were assigned to each participant. The hazard ratios (HRs) and 95% confidence intervals (CIs) of mortality using a Cox proportional hazard model were presented. Results We identified 2,789 all-cause deaths during the 470,178 person-years of follow-up. PM2.5 exposure had no significant association with all-cause and cause-specific mortality. The multivariable-adjusted HRs per 1 μg/m3 increase in the PM2.5 concentration were 0.94 (95% CI = 0.80-1.12) for coronary heart disease, 0.92 (95% CI = 0.81-1.04) for stroke and 1.09 (95% CI = 0.97-1.23) for non-malignant respiratory disease. Conclusions We observed little evidence of increased risk of all-cause and cause-specific mortality by long-term exposure to PM2.5 whose concentrations ranged from 8.3 to 13.1 μg/m3. A somewhat increased trend for non-malignant respiratory disease mortality may not be negligible. Key messages • We found little evidence of increased risk of all-cause and cause-specific mortality by long-term exposure to PM2.5. • Somewhat increased tendency for non-malignant respiratory disease mortality associated with PM2.5 exposure was observed.