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Exposure to particulate matter and long-term risk of cardiovascular mortality in Japan: NIPPON DATA80.

AIM
It remains uncertain whether chronic exposure to particulate air pollution is associated with increased mortality in Japan because Japan has a different distribution pattern of cardiovascular disease and its risk factors compared to Western countries. We investigated the association between long-term exposure to particulate matter (PM) and cardiovascular mortality risk using a representative Japanese cohort.


METHODS
A total of 7,250 participants aged 30 years and older from 232 districts throughout Japan were followed from 1980 to 2004. We linked the averaged annual concentrations of PM from 1985 to 2004 to each cohort participant who resided in the district at the time of the baseline survey. Study participants were divided into quintiles of average PM concentration. We applied the Cox proportional hazard model adjusting for sex, age, body mass index, blood pressure, total cholesterol, blood glucose, smoking categories, drinking categories, and the municipality population size.


RESULTS
During follow-up, there were 1,716 deaths from all causes; 571 from cardiovascular disease, 116 from coronary heart disease, and 250 from stroke. Hazard ratios were not different among the quintiles and those for trend per 10 µg/m3 increase in annual PM concentration were 0.98 (95% confidence interval, 0.92-1.04) for all-cause mortality and 0.90 (95% confidence interval, 0.81-1.00) for cardiovascular mortality.


CONCLUSION
Long-term exposure to PM was not associated with increased cardiovascular mortality risk in this population-based cohort in Japan.