Association Between the Combined Effects of Physical Activity Intensity and Particulate Matter and All-Cause Mortality in Older Adults

Objective: To investigate the association between the combined effects of physical activity (PA) intensity and particulate matter ≤10 μm in diameter (PM₁₀) and mortality in older adults. Methods: This nationwide cohort study included older adults without chronic heart or lung disease who engaged in regular PA. Physical activity was assessed by a standardized, self-reported questionnaire that asked the usual frequency of PA sessions with low (LPA), moderate (MPA), or vigorous intensity (VPA). Each participant's annual average cumulative PM₁₀ was categorized as low to moderate and high PM₁₀ on the basis of a cutoff value of 90th percentile. Results: A total of 81,326 participants (median follow-up, 45 months) were included. For participants engaged in MPA or VPA sessions, every 10% increase in the proportion of VPA to total PA sessions resulted in a 4.9% (95% CI, 1.0% to 9.0%; P=.014) increased and 2.8% (95% CI, −5.0% to −0.5%; P=.018) decreased risk of mortality for those exposed to high and low to moderate PM₁₀, respectively (P_interaction, <.001). For participants engaged only in LPA or MPA sessions, every 10% increase in the proportion of MPA to total PA sessions resulted in a 4.8% (95% CI, −8.9% to −0.4%; P=.031) and 2.3% (95% CI, −4.2% to −0.3%; P=.023) decreased risk of mortality for those exposed to high and low to moderate PM₁₀, respectively (P_interaction, .096). Conclusion: We found that for the same level of total PA, MPA was associated with delayed mortality whereas VPA was associated with hastened mortality of older adults in high levels of PM₁₀.