Association of PM2.5 exposure with hospitalization for cardiovascular disease in elderly individuals in Japan

Although exposure to particulate matter with aerodynamic diameters ≤ 2.5 µm (PM2.5) influences cardiovascular disease (CVD), its association with CVD-related hospitalizations of super-aged patients in Japan remains uncertain. We investigated the relationship between short-term PM2.5 exposure and CVD-related hospitalizations, lengths of hospital stays, and medical expenses. We analyzed the Japanese national database of patients with CVD (835,405) admitted to acute-care hospitals between 2012 and 2014. Patients with planned hospitalizations and those with missing PM2.5 exposure data were excluded. We classified the included patients into five quintiles based on their PM2.5 exposure: PM-5, -4, -3, -2, and -1 groups, in descending order of concentration. Compared with the PM-1 group, the other groups had higher hospitalization rates. The PM-3, -4, and -5 groups exhibited increased hospitalization durations and medical expenses, compared with the PM-1 group. Interestingly, the hospitalization period was longer for the ≥ 90-year-old group than for the ≤ 64-year-old group, yet the medical expenses were lower for the former group. Short-term PM2.5 exposure is associated with increased CVD-related hospitalizations, hospitalization durations, and medical expenses. The effects of incident CVDs were more marked in elderly than in younger patients. National PM2.5 concentrations should be reduced and the public should be aware of the risks.