Correlation Between Body Composition and Physical Function in Middle-Aged and Older Adults: The Moderating Role of Multimorbidity

Background and Purpose: Body composition is correlated to physical function, however there is limited evidence about the contribution of multimorbidity in the relationship. This study aimed to examine the moderating effect of multimorbidity on the relationship between body composition and physical function in middle-aged and older adults. Methods: This was a cross-sectional study where baseline data of 476 subjects (65.80 ± 8.56 years old, 73% women) who attended the training study were included. Inclusion criteria for participants were community-dwelling, aged greater than 50, and could walk independently. Body fat percentage (%BF) and appendicular skeletal muscle mass index (ASMI) were evaluated using dual energy X-ray absorptiometry. Assessment of physical function included mobility/agility (timed up and go test [TUG]) and muscle strength (grip strength test). Multimorbidity was defined when an individual had at least two chronic diseases. Hayes, process macro was used to analyze the moderating role of multimorbidity. Results: Multimorbidity significantly moderated the correlation of ASMI and grip strength (β = -1.617, p = 0.020) where the positive correlation between ASMI and grip strength was stronger in middle-aged and older adults without multimorbidity compared to that in individuals with multimorbidity. Multimorbidity also moderated the correlation between ASMI and TUG (β = 0.315, p = 0.049) where the positive correlation between ASMI and TUG was stronger in middle-aged and older adults with multimorbidity compared to that in individuals without multimorbidity. Multimorbidity did not moderate the correlation between %BF and grip strength (β = 0.076, p = 0.436) and the correlation between %BF and TUG in middle-aged and older adults (β = -0.005, p = 0.809). Conclusions: For middle-aged and older adults, the relationship between muscle mass and physical function is moderated by multimorbidity. The advantage of greater muscle mass on muscle strength is more evident in individuals without multimorbidity. The disadvantage of greater muscle mass on agility is more evident in individuals with multimorbidity. Clinical Relevance: Clinicians should be more sensitive about multimorbidity of patients because it moderates the correlation between body composition and physical function. Clinicians could therefore tailor the individualized treatment plan.