The Loss of Skeletal Muscle Strength, Mass, and Quality in Older Adults: The Health, Aging and Body Composition Study

TLDR

Loss of muscle mass is a major determinant of strength loss in aging. The study aimed to examine the longitudinal association between muscle mass loss and strength decline in older adults. Researchers measured knee extensor strength by isokinetic dynamometry and assessed whole‑body and appendicular lean and fat mass using dual‑energy X‑ray absorptiometry and computed tomography in 1,880 participants over three years. Strength declined faster than muscle mass, with men losing nearly twice as much as women, Blacks losing ~28% more than Whites, and annual leg strength loss about three times the rate of leg lean mass loss; lean mass loss, higher baseline strength, lower baseline leg lean mass, and older age predicted decline, yet increases in lean mass did not preserve strength, indicating a loss of muscle quality.

Abstract

The loss of muscle mass is considered to be a major determinant of strength loss in aging. However, large-scale longitudinal studies examining the association between the loss of mass and strength in older adults are lacking.Three-year changes in muscle mass and strength were determined in 1880 older adults in the Health, Aging and Body Composition Study. Knee extensor strength was measured by isokinetic dynamometry. Whole body and appendicular lean and fat mass were assessed by dual-energy x-ray absorptiometry and computed tomography.Both men and women lost strength, with men losing almost twice as much strength as women. Blacks lost about 28% more strength than did whites. Annualized rates of leg strength decline (3.4% in white men, 4.1% in black men, 2.6% in white women, and 3.0% in black women) were about three times greater than the rates of loss of leg lean mass ( approximately 1% per year). The loss of lean mass, as well as higher baseline strength, lower baseline leg lean mass, and older age, was independently associated with strength decline in both men and women. However, gain of lean mass was not accompanied by strength maintenance or gain (ss coefficients; men, -0.48 +/- 4.61, p =.92, women, -1.68 +/- 3.57, p =.64).Although the loss of muscle mass is associated with the decline in strength in older adults, this strength decline is much more rapid than the concomitant loss of muscle mass, suggesting a decline in muscle quality. Moreover, maintaining or gaining muscle mass does not prevent aging-associated declines in muscle strength.