Long-term air pollution exposure and incident physical disability in older US adults: a cohort study

Background: Disability is a key marker of overall physical health in older adults and is often preceded by chronic disease. Although air pollution is a well recognised risk factor for multiple chronic diseases, its association with physical disability has not been well characterised. We investigated the associations of air pollutants with physical disability in a large cohort representative of older adults in the USA. Methods: We used biennial data on incident activities of daily living (ADL) disability collected from respondents of the Health and Retirement Survey between 2000 and 2016. As part of the Environmental Predictors of Cognitive Health and Aging study, we estimated 10-year average PM2·5, PM10–2·5, nitrogen dioxide (NO2), and ozone (O3) concentrations at participant residences before each survey using spatiotemporal prediction models. We used a time-varying, weighted Cox model to estimate hazard ratios (HRs) for incident physical disability per interquartile increase of air pollution with detailed adjustments for confounders. Findings: Among 15 411 respondents aged 65 years and older (mean age 70·2 [SD 6·5] years; 55% female, 45% male), 48% of respondents reported newly having ADL disability during a mean follow-up of 7·9 years (SD 4·7). In fully adjusted models, we found greater risks of ADL disability associated with higher concentrations of PM2·5 (HR 1·03 per 3·7 μg/m³ [95% CI 0·99–1·08], p=0·16), PM10–2·5 (1·05 per 4·9 μg/m³ [1·00–1·11], p=0·022), and NO2 (1·03 per 7·5 ppb [0·99–1·08]. p=0·064), although not all these associations were statistically significant. In contrast, O3 was associated with a lower risk of ADL disability (0·95 per 3·7 ppb [0·91–1·00], p=0·030). In a multi-pollutant model, associations were similar to the single-pollutant models for PM10–2·5 (1·05 per 4·9 μg/m³ [1·00–1·11], p=0·041) and O3 (0·94 per 3·7 ppb [0·88–1·01], p=0·083). Interpretation: Our findings suggest that air pollution might be an underappreciated risk factor for physical disability in later life, although additional research is needed. Funding: National Institutes of Environmental Health Sciences and National Institute on Aging.