Long-term exposure to fine particle matter and all-cause mortality and cause-specific mortality in Japan: the JPHC Study
Norie Sawada, Tomoki Nakaya, Saori Kashima, Takashi Yorifuji, Tomoya Hanibuchi, Hadrien Charvat, Taiki Yamaji, Motoki Iwasaki, Manami Inoue, Hiroyasu Iso, Shoichiro Tsugane
Abstract
Abstract Background Many epidemiological studies have reported the association between exposure to particulate matter and mortality, but long-term prospective studies from Asian populations are sparse. Furthermore, associations at low levels of air pollution are not well clarified. Here, we evaluated associations between long-term exposure to particulate matter <2.5 µg/m 3 (PM 2.5 ) and mortality in a Japanese cohort with a relatively low exposure level. Methods The Japan Public Health Center-based Prospective Study (JPHC Study) is a prospective cohort study of men and women aged 40-69 years in 1990 who were followed up through 2013 for mortality. In this cohort of 87,385 subjects who did not move residence during follow-up, average PM 2.5 levels from 1998 to 2013 by linkage with 1-km 2 grids of PM 2.5 concentration were assigned to the residential addresses of all participants. To avoid exposure misclassification, we additionally evaluated the association between 5-year (1998-2002) cumulative exposure level and mortality during the follow-up period from 2003 to 2013 in 79,078 subjects. Cox proportional hazards models were used to calculate the association of long-term exposure to PM 2.5 on mortality, with adjustment for several individual confounding factors. Results Average PM 2.5 was 11.6 µg/m 3 . Average PM 2.5 exposure was not associated with all-cause mortality or cancer and respiratory disease mortality. However, average PM 2.5 was positively associated with mortality from cardiovascular disease (hazard ratio (HR) of 1.23 (95%CI=1.08-1.40) per 1-µg/m 3 increase; in particular, HR in mortality from cerebrovascular disease was 1.34 (95%CI=1.11-1.61) per 1-µg/m 3 increase. Additionally, these results using cumulative 5-year PM 2.5 data were similar to those using average PM 2.5 over 15 years. Conclusions We found evidence for a positive association between PM 2.5 exposure and mortality from cardiovascular disease in a Japanese population, even in an area with relatively low-level air pollution.