Objective: The purpose of this study was to explore the association between body composition in the elderly and subsequent changes in muscle strength during aging.
Methods: This was a longitudinal study with a 5-y follow-up. Eighty-seven men (n = 38) and women (n = 49) from a random sample of 75-y-old subjects in the Göteborg part of the Nordic Research on Aging study who were investigated at ages 75 and 80 y and were free from any major diseases at baseline were included. Body composition was estimated from bioelectrical impedance. The maximal isometric strengths of handgrip, arm flexion, and knee extension were measured on the side of the dominant hand while a subject was in a sitting position in an adjustable dynamometer chair.
Results: Fat-free mass decreased significantly (P < 0.001) in both sexes, but more in men. Percentage of body fat increased only in men (P < 0.05). Body height decreased in both sexes, but more in women (P < 0.001). Declines in muscle strengths were evident for all muscle groups in both sexes but more prominent in men. It was observed that body composition status at baseline, measured as fat-free mass and fat-free mass index, was a statistically significant predictor for decline in muscle strength, particularly in the extremities.
Conclusion: Fat-free mass at age 75 y was associated with lower 5-y decline in muscle strength. This finding underscores the potential importance of fat-free mass for maintaining functional ability during aging.