To examine patterns of muscle mass change with aging and to estimate the prevalence of sarcopenia.

Cross-sectional survey.

Population-based study in Rochester, Minnesota.

Age-stratified sample of men and women from the community.

Muscle mass estimated from total body scans by dual-energy X-ray absorptiometry. Sarcopenia was defined as muscle mass more than 2 standard deviations below the sex-specific young-normal mean.

Total lean body mass (exclusive of bone) and total skeletal muscle mass both were greater in men than women and declined linearly with age as judged from these cross-sectional data. Adjustment for height reduced the gender difference. The age- and sex-adjusted prevalence of sarcopenia varied from 6 to 15% among subjects 65 years of age or over, depending on the muscle mass parameter that was evaluated, but prevalence rates were quite sensitive to the normal values used to define cutoff levels. Subjects with sarcopenia appeared to have more physical limitations than the others.

Late in life, a substantial portion of the population reaches low levels of muscle mass that are associated with increased physical disability. However, additional efforts are needed to validate an operational definition of sarcopenia.