Exposure-Response to High PM_2.5 Levels for Cardiovascular Events in High-Risk Older Adults in Taiwan

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/m³ 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.

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.

We included 373 402 older adults with high-risk conditions in Taiwan. Using the PM_2.5 concentration <15 μg/m³ (Taiwan regulatory standard) as a reference, the seasonal average PM_2.5 concentrations (15-23.5 and >23.5 μg/m³) 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.

Further lowering PM_2.5 levels beyond current regulatory standards (15 μg/m³) 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.