Techniques of assessing muscle mass and function (sarcopenia) for epidemiological studies of the elderly.

For epidemiological studies, reliable and valid measurements or indices of muscle mass are needed to screen for those elderly persons at risk for sarcopenia, and to determine the prevalence of these conditions on a national level. The methods more suitable for field or epidemiological settings are anthropometry, bioelectrical impedance, and grip strength. These field methods, while reliable, have limited demonstrated validity in their application to the elderly and are restricted by the limited functional capabilities of the elderly, which decrease with age. Epidemiological studies of the elderly need to include sufficient numbers of persons of different ethnic backgrounds, and at the older ages. For an epidemiological study of the elderly today, one also needs to select the categories of elderly persons to be included in such studies: healthy, sick, very old, handicapped, level of functional status, etc., because relationships among variables can have different statistical and biological associations. Future work should be directed at improving the design and methodology of epidemiological and serial studies so as to maximize the numbers and categories of elderly persons who can be studied.