Robert D. Lindeman

Muscle mass decreases with age, leading to "sarcopenia," or low relative muscle mass, in elderly people. Sarcopenia is believed to be associated with metabolic, physiologic, and functional impairments and disability. Methods of estimating the prevalence of sarcopenia and its associated risks in elderly populations are lacking. Data from a population-based survey of 883 elderly Hispanic and non-Hispanic white men and women living in New Mexico (the New Mexico Elder Health Survey, 1993-1995) were analyzed to develop a method for estimating the prevalence of sarcopenia. An anthropometric equation for predicting appendicular skeletal muscle mass was developed from a random subsample (n = 199) of participants and was extended to the total sample. Sarcopenia was defined as appendicular skeletal muscle mass (kg)/height2 (m2) being less than two standard deviations below the mean of a young reference group. Prevalences increased from 13-24% in persons under 70 years of age to >50% in persons over 80 years of age, and were slightly greater in Hispanics than in non-Hispanic whites. Sarcopenia was significantly associated with self-reported physical disability in both men and women, independent of ethnicity, age, morbidity, obesity, income, and health behaviors. This study provides some of the first estimates of the extent of the public health problem posed by sarcopenia.

Serial creatinine clearances (5 to 14 studies) were obtained for 446 normal volunteers in the Baltimore Longitudinal Study of Aging followed between 1958 and 1981. When those subjects with possible renal or urinary tract disease and subjects on diuretics and antihypertensives were removed from the study, leaving a group of 254 "normal" subjects, the mean decrease in creatinine clearance was 0.75 ml/min/year. The slopes of the creatinine clearance vs. time fell into a normal (Gaussian) distribution around this mean. One third of all subjects followed had no absolute decrease in renal function (positive slope of creatinine clearance vs. time) and there was a small group of patients who showed a statistically significant increase (P less than 0.05) in creatinine clearance with age.

Although clinical magnesium deficiency is now recognized frequently in chronic alcoholics, its cause or causes are not clear. A poor dietary intake is undoubtedly important, but it is unlikely that magnesium deficiency results from dietary depletion alone, since it has been quite difficult to produce experimental dietary magnesium defi- ciency in man (2). Earlier workers have shown that the kidneys are reasonably efficient in con- serving magnesium (2, 3). Thus, it is likely that some additional mechanism may be respon- sible for magnesium deficiency associated with chronic alcoholism. Recent studies have indicated that ethanol may induce increased urinary ex- cretion of magnesium (4, 5). The purpose of the present study was to determine the effect of an acute ethanol load on urinary excretion of mag- nesium and other electrolytes, and to make pre- liminary observations on the mechanism respon- sible for an observed increase in urinary excretion of magnesium.

The objective of this investigation was to test the hypothesis that blood glutathione levels are lower in aging human subjects as previously found in blood and tissues of standard rodent models of aging. Thus a study was conducted with 39 men and 130 women, 20 to 94 years old, who were selected by the criteria of being ambulatory, healthy, and free from diabetes mellitus, thyroid disease, anemias, and cancer. The reference group was comprised of the 20- to 39-year-old subjects, whose blood glutathione levels were 547 +/- 53.5 micrograms/10(10) erythrocytes (mean +/- SD) for 40 individuals and defined the reference range (95% confidence limits) of 440 to 654. Based on the 440 micrograms/10(10) erythrocyte cutoff, the incidence of low blood glutathione content in the older subjects increased significantly, particularly in the 60- to 79-year-old group. Their glutathione levels were 452 +/- 86.8 micrograms/10(10) erythrocytes, 17% lower than the reference group (p < 0.001). These findings demonstrate an increased incidence of low glutathione levels in apparently healthy elderly subjects, who thus may be at risk because of a decreased capacity to maintain many metabolic and detoxification reactions mediated by glutathione.