Traffic-related air pollutant exposure and physical performance in the Adult Changes in Thought cohort

Declining physical function is common among older adults and is associated with reduced quality of life. There is little research on the relationship between air pollution and physical limitations, though exposure to air pollution is associated with many chronic conditions that lead to worsening physical function. This is especially true for several traffic-related air pollutants (TRAPs), as these pollutants can enter the circulatory system and lead to systemic inflammation.

We conducted a longitudinal analysis in the Adult Changes in Thought study, a cohort of 5,305 older adults in the Puget Sound region of Washington state enrolled between 1994-2020. We estimated long-term average air pollution concentrations at residential addresses using spatial prediction models and examined associations between several TRAPs (BC, NO₂, and UFPs of various size ranges) and physical performance assessed using a modified version of the Short Physical Performance Battery (score 0-12). This measure combines three physical functioning assessments: chair-stand time, gait speed, and grip strength. We used linear mixed models to understand whether pollutant exposure was associated with physical performance, both cross-sectionally at baseline and longitudinally after adjustment for other risk factors.

In models adjusted for baseline age, sex, race/ethnicity, education, neighborhood deprivation index and behavioral risk factors, 124 ng/m³ higher 5-year average BC and 2.1 ppb higher 5-year NO₂ exposure were suggestive of faster declines in physical performance (-0.046; 95 % CI: -0.096, 0.004) and (-0.032; 95 %CI: -0.074, 0.01), equivalent to an additional 2.6 months (-0.4, 5.6) and 1.8 months (-0.7, 4.3) of aging over 5 years, respectively. Higher UFP exposure was not associated with changes in physical performance over time.

This work suggests that air pollution from traffic may impact the physical function of older adults, though more research is needed to confirm these findings.