Objectively measured the impact of ambient air pollution on physical activity for older adults

Abstract Background Air pollution poses a significant health risk to the human population, especially for vulnerable groups such as the elderly, potentially discouraging their engagement in physical activity. However, there is a lack of sufficient objective and longitudinal data in current research on how air pollution affects physical activity among older adults. With these gaps, we aimed to explore the relationship between air pollution and objective measurement-based physical activity among older adults by engaging in a longitudinal study design. Methods A total of 184 older adults were recruited from three cities with varying levels of air quality. Mean daily minutes of physical activity were measured with 7 consecutive days of accelerometer monitoring (ActiGraph GT3X-BT). Corresponding air pollution data including daily PM 2.5 (µg/m 3 ), PM 10 (µg/m 3 ) and air quality index (AQI) were sourced from the China National Environmental Monitoring Centre at monitor locations close to older adults’ addresses. Associations between air quality and physical activity were estimated using a fixed effect model, adjusting for average daytime temperature, rain, age and weight. Results AQI and PM 2.5 were observed to exhibit significant, inverse, and linear associations with mean daily walk steps, minutes of light physical activity (LPA), moderate physical activity (MPA) and moderate-to-vigorous physical activity (MVPA) in the single variable models. A one-level increase in AQI corresponded to a decline in 550.04 steps (95% CI = -858.97, -241.10; p < 0.001), 10.43 min (95% CI = -17.07, -3.79; p < 0.001), 4.03 min (95% CI = -7.48, -0.59; p < 0.001) and 4.16 min (95% CI = -7.77, -0.56; p < 0.001) in daily walking steps, LPA, MPA, and MVPA, respectively. A one-level increase in PM 2.5 correlated with a decline in daily walk steps, LPA, MPA and MVPA by 361.85 steps (95% CI = -516.53, -207.16; p < 0.001), 8.97 min (95% CI = -12.28, -5.66; p < 0.001), 3.73 min (95% CI = -5.46, -2.01; p < 0.001,) and 3.79 min (95% CI = -5.59, -1.98; p < 0.001), respectively. However, PM 10 displayed a significant negative association exclusively with LPA, with one-level increase in PM 10 resulting in a 3.7-minute reduction in LPA (95% CI = -6.81, -0.59, p < 0.05). Conclusion Air pollution demonstrates an inverse association with physical activity levels among older adults, potentially discouraging their engagement in physical activity. Different air quality indicators may exert varying impacts on physical activity. Future studies are warranted to enhance policy interventions aimed at reducing air pollution and promoting physical activity.