Trajectories of physical capacity among community-dwelling older adults in the United States

Objective: Although the prognostic value of physical capacity is well-established, less is known about longitudinal patterns of physical capacity among community-dwelling older adults. We sought to describe long-term trajectories of physical capacity in a nationally representative sample of Medicare beneficiaries. Design: Cohort study Setting and Participants: Annually collected data on 6,783 community-dwelling participants in the National Health and Aging Trends Study from 2011 to 2016 were analyzed. Methods: Performance-based physical capacity was measured using the Short Physical Performance Battery [(SPPB) range: 0-12, higher is better]. Self-reported physical capacity was measured using six pairs of activities with composite scores from 0 to 12 (higher is better). We then used group-based trajectory modeling to identify longitudinal patterns of each physical capacity measure over 6 years. Associations of baseline characteristics with trajectories were examined using multinomial logistic regression. Results: The cohort was 57% female, 68% white, and 58% were >= 75 years. Six distinct trajectories of SPPB scores were identified. Two "high" groups (n = 2192, 43%) maintained high average SPPB scores. Two "moderate decline" groups (n = 1459, 29%) had a mid-range SPPB score at baseline and demonstrated gradual decline. A "low decline" group (n = 811, 16%) started with a low SPPB score and experienced a greater decline. A "very low" group (n = 590, 12%) had very low SPPB scores in all years. Six trajectories for self-reported physical capacity were also identified. Older age, worse health, lower income and education, and being Black or Hispanic were associated with lower and declining physical capacity.