Aim: Associations between long-term exposure to particulate matter (PM) and increased cardiovascular mortality have been reported, but few studies have investigated the associated incidence of cardiovascular disease, and none involved men.
Methods: We used data on 78,057 participants (37,121 men, 40,936 women) to examine the associations of long-term exposure to PM with mortality and the incidence of cardiovascular diseases. Average PM levels in the relevant area during the study period were used as an index of individual exposure to each subject. Cox models adjusted for age, sex, smoking, environmental smoking, body mass index, and alcohol consumption were used, with further adjustments for nitrogen dioxide and sulfur dioxide exposure, systolic blood pressure, total cholesterol, and diabetes mellitus.
Results: Increased PM levels were associated with an increased risk of incident coronary heart disease (CHD) and myocardial infarction (MI), particularly among smokers (adjusted hazard ratio (HR) per 10 µg/m(3) increase in PM for CHD: 1.39, 95% confidence interval (CI) 1.01-1.93; for MI: 1.52, 1.08-2.13) and among women (for CHD: 1.63, 0.91-2.92; for MI: 1.99, 1.07-3.70); however, the observed positive association of PM exposure with the incidence of CHD and MI was not robust, and the association disappeared when one of the areas (Akita) was excluded. The association with CHD mortality was not statistically significant (adjusted HR per 10 µg/m(3) increase in PM: 1.11, 0.92-1.33). There was an inverse association of long-term PM exposure with stroke mortality and incidence. There was no clear association between PM levels and lung cancer mortality and incidence.
Conclusions: Long-term exposure to PM might increase the risk of incident CHD in middle-aged Japanese men and women. Our findings also suggest that women and smokers are especially vulnerable to PM exposure.