Low-Level Airborne Particulate Matter and Risk of Hypertension Hospitalization in Older U.S. Adults.

Abstract (English)

BACKGROUND: Although long-term exposure to fine particulate matter (particles ≤ 2.5 μm in diameter [PM_2.5]) has been linked to adverse cardiovascular outcomes, evidence remains limited regarding the effects of PM_2.5 at concentrations below current regulatory standards on hypertension-related hospitalization. OBJECTIVES: In this study, we examined the association between long-term exposure to PM_2.5 concentrations below the U.S. Environmental Protection Agency annual standard of 9 μg/m³ and the risk of hypertension-related hospitalization among Medicare beneficiaries aged ≥65 years across the contiguous United States from 2017 to 2022 using a causal inference approach. METHODS: We constructed a national cohort of more than 26 million older adults from the Medicare database residing in ZIP codes where annual PM_2.5 concentrations consistently remained below 9 μg/m³ throughout the study period. To address unmeasured confounding, we used a double-negative control approach. Secondary analyses compared the main findings with results from conventional quasi-Poisson regression models and examined effect modification by population subgroups. RESULTS: Each 1-μg/m³ increase in the annual PM_2.5 concentration was associated with a 2.8% (95% CI: 2.5-3.2) increase in hypertension-related hospitalization among all beneficiaries, comparable with estimates from conventional quasi-Poisson regression models. Greater vulnerability was observed among women, residents of the Midwest and Northeast, those living in rural or suburban areas, and individuals in more socioeconomically deprived neighborhoods. CONCLUSIONS: These findings suggest that even PM_2.5 exposures below current regulatory thresholds in the United States may contribute to increased hypertension risk, emphasizing the need to reconsider existing air quality standards to better protect public health.