Abstract
IMPORTANCE: Physical disability reflects the cumulative burden of chronic conditions. Although generally progressive, episodes of disability can be followed by periods of recovery; therefore, there is a need to identify modifiable risk factors that contribute to the dynamic development of disability. OBJECTIVE: To investigate air pollution as a modifiable risk factor of transitions between states of no physical function limitation, physical function limitations, and activities of daily living (ADL) disability. DESIGN, SETTING, AND PARTICIPANTS: This cohort study included respondents older than 50 years from the nationally representative Health and Retirement Study (HRS) who participated in at least 2 interviews between 2000 and 2016. Data analysis was conducted from July 2023 to August 2025. EXPOSURES: Ten-year average ambient concentrations of particulate matter with a diameter of 2.5 µm or less (PM2.5), PM with a diameter between 10 and 2.5 µm (PM10-2.5), nitrogen dioxide (NO2), and ozone (O3) were estimated at respondent residential addresses preceding each survey using spatiotemporal models. MAIN OUTCOMES AND MEASURES: Physical disability states were assessed using self-reported mobility and Activities of Daily Living (ADL). To examine associations of exposure to air pollution with transitioning between states of physical disability, multistate models, adjusted for individual- and area-level covariates, were used. RESULTS: The sample included 29 790 respondents (mean [SD] age, 63 [11] years; 16 878 [57%] women; 3371 [11%] Hispanic, 5240 [18%] non-Hispanic Black, and 20 314 [68%[ non-Hispanic White), who were followed up for a mean (SD) of 8 (6) years. IQR-increments in PM2.5, PM10-2.5, and NO2 concentrations were mostly associated with greater hazards of transitioning from a state of no physical function limitation toward disability; a 1-IQR increment for PM2.5 was associated with lower odds of a reverse transition. For example, in the single-pollutant model, a 1-IQR higher PM2.5 concentration was associated with a hazard ratio (HR) of 1.06 (95% CI, 1.03-1.09) for transitioning from no physical function limitations to physical function limitations and an HR of 0.96 (95% CI, 0.93-0.99) for reverting back to healthy physical function from physical function limitations. By contrast, a 1-IQR higher O3 concentration was associated with lower hazards of transitioning from no physical function limitations to physical function limitations (HR, 0.92; 95% CI, 0.86-0.98) and ADL disability (HR, 0.89; 95% CI, 0.81-0.97). CONCLUSIONS AND RELEVANCE: These findings suggest that air pollution may affect the progression of physical disability and hinder recovery in later life.