Chronic diseases related to poor lifestyle behaviors account
for more than two-thirds of deaths in the United States (17).
Population-based studies assess diet and physical activity and
measure indexes such as blood lipids, body mass index, and bone
biomarkers to predict risk of disease. Few if any populationbased
studies have assessed muscle mass or physical or metabolic
function to understand the role of muscle in these conditions.
However, alterations in muscle play an important role in
the most common diseases and conditions. Heart disease and
cancer are the major chronic diseases suffered in the United
States (17). Both cardiac failure and cancer are often associated
with rapid and extensive loss of muscle mass, strength, and metabolic
function (cachexia).With cardiac and cancer cachexia, the
loss of muscle mass is an important determinant of survival (14,
18). Sarcopenia, the progressive loss of muscle mass and function
that occurs with aging, is a widespread syndrome that has a
devastating effect on quality of life and ultimately survival (19).
Progressive sarcopenia is ultimately central to the development
of frailty, an increased likelihood of falls, and impairment of the
ability to perform ADL (19). The logical endpoint of severe
sarcopenia is loss of quality of life and ultimately institutionalization.