Association of PM_2.5 exposure with hospitalization for cardiovascular disease in elderly individuals in Japan

Although exposure to particulate matter with aerodynamic diameters ≤ 2.5 µm (PM_2.5) 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 PM_2.5 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 PM_2.5 exposure data were excluded. We classified the included patients into five quintiles based on their PM_2.5 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 PM_2.5 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 PM_2.5 concentrations should be reduced and the public should be aware of the risks.