The effect-modification of physical activity on the association of pain with impaired physical function in aging adults.

Objectives: Pain is prevalent among older adults and may result in impairment in physical function. However, little is known about the effect-modification of this relationship by physical activity (PA) participation. This large and representative study sought to estimate the effect of pain on physical function among older adults in Ghana and evaluate whether PA modifies this association.

Methods: Data came from 1201 adults aged ≥50 years participating in the AgeHeaPsyWel-HeaSeeB Study in Ghana. Pain constructs were defined using the Medical Outcomes Study Short Form-36 (MOS SF-36). PA was assessed using the International Physical Activity Questionnaire short form (IPAQ-SF) and physical function impairment was measured by seven-item domains based on the activities of daily living (ADL) and instrumental ADL (IADL). Adjusted hierarchical OLS regressions were fitted to estimate the direct and moderating relationships between pain facets, PA, and impaired physical function.

Results: The relationships of pain severity (β = 0.348, p < .001), and pain interference (β = 0.424, p < .001) with impaired physical function were robust after full adjustment for confounding variables. Persons with pain experiences had significantly increased impaired physical function risks. PA significantly modified the association between pain severity (β = -0.232, p < .001) and pain interference (β = -0.143, p < .001) with impaired physical function.

Conclusions: Our data indicate that the relationships of pain with physical function impairment are modified by PA intensity. Future studies are warranted to understand the indirect effect of pain on functional limitations and how PA promotion could manage pain and improve functional ability in aging adults.