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 (PM) 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 PM was categorized as low to moderate and high PM 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 PM, respectively (P, <.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 PM, respectively (P, .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 PM.