Research hypotheses on muscle wasting, aging, loss of function and disability.

Advancing age is accompanied by modifications in body composition such as increase in fat and decrease in bone and muscle mass. Loss of muscle mass or sarcopenia is characterized by a decrease in the total number of muscle fibers, a reduced cross-sectional area of the thigh, and decreased muscle density associated with increased intramuscular fat. Loss of skeletal muscle mass may be a common pathway by which multiple diseases contribute to the risk of disability. Decreases in muscle mass are associated with an increased risk of morbidity, mortality and disability in old age, but the mechanisms by which this occurs are not fully understood. Inflammatory cytokines interfere with muscle contraction and are linked with sarcopenia. Recent evidence showing that decline in left ventricular function is accompanied by sarcopenia and an increase in cytokines might help to understand the role of cytokines in muscle loss in aging and disease. The Health and Body Changes (Health ABC) study, a large population-based cohort study sponsored by the National Institute on Aging, will prospectively address the issues related to sarcopenia and incident disability. Defining modifiable risk factors of sarcopenia is the first step towards the identification of interventions for preventing or reversing disability in older persons.