Joint effects of physical functioning limitations and impaired lung function on all-cause mortality in middle-aged...

Impairments in physical and pulmonary function are common in later life and are individually associated with increased mortality risk. However, their joint effects and variation across physical functioning domains remain underexplored.

Impaired physical functioning was defined as difficulty in any domain: overall mobility (OM), upper body mobility (UBM), lower body mobility (LBM), and activities of daily living (ADL). Lung function impairment was determined using reduced peak expiratory flow (PEF). Weighted Cox regression was employed to assess averaged hazard ratio (AHR) for mortality among 12,621 Chinese adults from a nationally representative cohort.

1685 deaths were recorded during a mean follow-up of 8.61 years. After adjusting for confounders, each 1-SD decrease in PEF increased the mortality risk by 32%. All physical functioning domains significantly associated with mortality, with adjusted AHR ranging from 1.33 for impaired LBM to 1.66 for impaired UBM. Impaired UBM and ADL were linked to elevated AHRs regardless of lung function status. Conversely, impaired OM or LBM was associated with increased mortality risk only among those with impaired PEF, with their coexistence resulting in a ∼50% increase in relative excess mortality risk due to interaction. Causal mediation analysis showed that lung function more strongly mediated the association between physical functioning and mortality than the reverse.

Lung function and physical functioning interact to jointly influence all-cause mortality risk in middle-aged and older Chinese adults, with effects varying across different domains of physical functioning, highlighting the importance of integrated assessments and targeted interventions to maximize lifespan-prolonging benefits.