Associations of Pain Characteristics with Physical Capacity Trajectories Among Older Adults in the United States.

Objective: We investigated the associations of pain characteristics with trajectories of physical capacity in older adults and determined if bothersome and activity-limiting pain modified the association between the number of chronic conditions and trajectories of physical capacity.

Methods: We performed a cohort study with 6,783 community-dwelling adults ≥65 years old who participated in the National Health and Aging Trends Study from 2011-2016. We assessed baseline pain characteristics and the number of self-reported chronic conditions (0-12) at baseline. Longitudinal physical capacity outcomes were categorized using previously identified performance-based and self-reported trajectory groups from this cohort. Multinomial logistic regression examined associations of pain characteristics with trajectories of physical capacity, adjusting for demographic and health characteristics. We then tested for effect modification using an interaction term in regression models.

Results: Participants who reported bothersome pain, activity-limiting pain, greater number of pain sites, and more frequent pain medication use at baseline were significantly more likely to demonstrate either "consistently very low" or declining physical capacity trajectories compared to a "consistently high" trajectory. The negative impact of chronic disease burden on risk of a declining trajectory for both performance-based and self-reported physical capacity was greater in those with bothersome pain versus those not reporting pain.

Discussion: Overall, we found bothersome pain and other pain characteristics were significantly associated with poor and worsening trajectories of physical capacity in older adults. This suggests pain is an important prognostic factor for targeting population-level interventions addressing physical capacity.