Predictors of skeletal muscle mass in elderly men and women

Background: Elderly men and women lose muscle mass and strength with increa sing age. Decreased physical activity, hormones, malnutrition and chronic d isease have been identified as factors contributing to this loss. There are few data, however, for their multivariate associations with muscle mass an d strength. This study analyzes these associations in a cross-sectional sam ple of elderly people from the New Mexico Aging Process Study. Methods: Dat a collected in 1994 for 121 male and 180 female volunteers aged 65-97 years of age enrolled in The New Mexico Aging Process Study were analyzed. Body composition was measured using dual energy X-ray absorptiometry; dietary in take from 3 day food records: usual physical activity by questionnaire; hea lth status from annual physical examinations; and serum testosterone? estro ne, sex-hormone binding globulin (SHBG), and insulin-like growth factor (IG F1) from radioimmunoassays of fasting blood samples. Statistical analyses i ncluded partial correlation and stepwise multiple regression. Results: The muscle mass and strength (adjusted for knee height) decreased with increasi ng age in both sexes. The muscle mass was significantly associated with ser um free-testosterone; physical activity, cardiovascular disease, and IGF1 i n the men. In the women, the muscle mass was significantly associated with total fat mass and physical activity. Age was not associated significantly with muscle mass after controlling for these variables. Grip strength was a ssociated with age independent of muscle mass in both sexes. Estrogen (endo genous and exogenous) was not associated with muscle mass or strength in wo men. Conclusions: Age-related loss of muscle mass and strength occurs in re latively healthy, well-nourished elderly men and women and has a multifacto rial basis. Sex hormone status is an important factor in men but not in wom en. Physical activity is an important predictor of muscle mass in both sexe s. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.