Exposure–Response to High PM 2.5 Levels for Cardiovascular Events in High‐Risk Older Adults in Taiwan

Background Limited studies using individual‐level health outcome data exist from countries with a wider range of particulate matter with a diameter of <2.5 μm (PM 2.5 ) levels to illustrate the shape of the exposure–response curve across a wide PM 2.5 range, including >15 μg/m 3 PM 2.5 concentrations. Taiwan reduced PM 2.5 over time with its policies, which provide opportunities to illustrate the dose–response curves and how reductions of PM 2.5 over time correlated with cardiovascular events incidence in a nationwide sample. Methods Using data from the 2009 to 2019 Taiwan National Health Insurance Database linked to nationwide PM 2.5 data, we examined the magnitude of the exposure–response curve between seasonal average PM 2.5 level and cardiovascular events‐related hospitalizations among older adults at high risk for cardiovascular events. We used history‐adjusted marginal structural models including potential confounding by individual demographic factors, baseline comorbidities, and health service measures. Results We included 373 402 older adults with high‐risk conditions in Taiwan. Using the PM 2.5 concentration <15 μg/m 3 (Taiwan regulatory standard) as a reference, the seasonal average PM 2.5 concentrations (15–23.5 and >23.5 μg/m 3 ) were associated with hazard ratio of 1.13 (95% CI, 1.09–1.18) and 1.19 (95% CI, 1.14–1.24), 1.07 (95% CI, 1.03–1.11) and 1.14 (95% CI, 1.10–1.18), 1.22 (95% CI, 1.08–1.38) and 1.31 (95% CI, 1.16–1.48), 1.04 (95% CI, 0.98–1.10) and 1.10 (95% CI, 1.04–1.16), respectively, for heart failure, ischemic stroke/transient ischemic attack, deep vein thrombosis, and myocardial infarction/acute coronary syndrome. Conclusions Further lowering PM 2.5 levels beyond current regulatory standards (15 μg/m 3 ) may effectively reduce the incidence of heart failure, deep vein thrombosis, and ischemic stroke/transient ischemic attack, and can lead to tangible health benefits in the high‐risk older population.