Associations of Air Pollution and Gait Speed in Older Adults

Background: Air pollution is widely recognized as a threat to public health. The impact of long-term exposure to air pollution on gait speed trajectories over time have not been fully explored among US older adults. The specific aims of this study were to 1) examine the relationship between long-term exposure to air pollution and decline in gait speed among older adults, and 2) explore effect modification by cardiovascular disease status on the association.
Methods: We analyzed data from 3,022 older adults in a prospective cohort study conducted from 2000 to 2008. Long term exposure to fine particulate matter (PM2.5) and nitrogen dioxide (NO2) prior to study enrollment was estimated using state of the art prediction models. Gait speed at usual and rapid pace was assessed annually using a 15-feet timed walk test. Mixed effect models with random intercepts and slopes were fitted, adjusting for demographic and socioeconomic factors.
Results: Greater long-term PM2.5 exposure was related to faster gait speed decline at usual pace: one interquartile range higher 5-year average PM2.5 exposure was related to 0.048 m/s decline in gait speed (95% CI: -0.084, -0.024) over a 6-year study period adjusted for age, gender, race and ethnicity, education, smoking status, alcohol consumption, study site, and year since enrollment. Greater long-term NO2 exposure was associated with faster gait speed decline at both usual and rapid pace: one interquartile range higher 5-year average NO2 was associated with 0.078 m/s decline in usual pace gait (95% CI: -0.120, -0.042) and 0.042 m/s decline in rapid pace gait speed (95% CI: -0.078, -0.006) over 6-year period in adjusted models. The longitudinal association between air pollution and rapid gait speed decline was significant only in individuals with cardiovascular disease.
Conclusions: Long-term exposure to air pollution appears to be associated with faster progression in gait speed decline among older adults in four different locations in the US. Older adults with cardiovascular disease are more susceptible to the adverse effects of long-term exposure of air pollution and the progression in gait speed decline may be even faster among those with cardiovascular disease. Policies to reduce emission of air pollutants and interventions of avoid air pollution exposure or manage cardiovascular disease could contribute to the reduction in the burden of preventable institutionalization and hospitalization.