Are associations of leisure-time physical activity with mortality attenuated by high levels of chronic ambient fine particulate matter (PM 2.5 ) in older adults? A prospective cohort study.

Background and Purpose: Although leisure-time physical activity (PA) has established health benefits in older adults, it is equivocal if exercising in environments with high levels of PM _2.5 concentrations is equally beneficial for them. To explore the independent and joint associations of ambient PM _2.5 and PA with all-cause mortality among adults aged 60 or older and to assess the modifying effect of age (60-74 years vs. 75+ years) on the joint associations.
Methods: A prospective cohort study based on the MJ Cohort repeat examinations (2005-2016) and the Taiwan Air Quality Monitoring Network and death registry linkages (2005-2022). We included MJ Cohort participants aged 60 or more at baseline who attended the health check-ups at least twice (n = 21,760). Metabolic equivalent hours per week (MET-h/week) of leisure-time PA were computed. Multivariable adjusted associations were examined using time-varying Cox proportional hazard models.
Results: There were 3539 all-cause deaths over a mean follow-up of 12.81 (SD = 3.67) years. Ambient PM _2.5 and physical inactivity are both independently associated with all-cause mortality. The joint associations of PA and PM _2.5 concentrations with all-cause mortality differed in the young-old (60-74 years) and the older-old (75+ years) (P for interaction = 0.01); Higher levels of long-term PM _2.5 exposures (≥25 μg/m ³ ) had little influence on the associations between PA and mortality in the young-old (HR = 0.68 (0.56-0.83) and HR = 0.72 (0.59-0.88) for participants with 7.5-<15 and 15+ MET-h/week respectively) but eliminated associations between exposure and outcome in the older-old (HR = 0.91 (0.69-01.21) and HR = 1.02 (0.76-1.38) for participants with 7.5-<15 and 15+ MET-h/week).
Conclusion: Long-term exposures to higher PM _2.5 concentrations may eliminate the beneficial associations of PA with all-cause mortality among adults aged 75 and over.
Competing Interests: Declaration of competing interest The authors do not have any conflict of interest to report.
(Copyright © 2023. Published by Elsevier Inc.)