Longitudinal Changes in Physical and Cognitive Functions among Participants with and without Rheumatoid Arthritis in Community-Dwelling Middle-Aged and Older Adults

BACKGROUND: This study evaluated the chronological changes in physical and cognitive functions in middle-aged and older adults with and without rheumatoid arthritis (RA). METHODS: This population-based case-control longitudinal study included individuals aged 40–79 years at baseline who agreed to participate. We identified 42 participants with RA and randomly selected 84 age- and sex-matched controls. Physical function was assessed according to gait speed, grip strength, and skeletal muscle mass. Cognitive function was assessed based on the information, similarities, picture completion, and digit symbol substitution test scores of the Wechsler Adult Intelligence Scale-Revised Short Form. The general linear mixed models comprised the fixed effects of the intercept, case, age, time in years since baseline, and case×time interaction, which were used to examine longitudinal changes in physical and cognitive functions. RESULTS: Regardless of RA status, grip strength decreased and the picture completion score increased in the group aged <65 years, while skeletal muscle mass index and gait speed decreased in the group aged ≥65 years. The interaction of case×follow-up years for grip strength in the group aged ≥65 years was significant (p=0.03). The decline in grip strength in the control group (slope=-0.45) was greater than that in the RA group (slope=-0.19). CONCLUSION: Chronological changes in physical and cognitive functions were comparable between participants with and without RA; however, the decline in grip strength in the control group was greater among older adults with RA.