Determinanten en consequenties van sarcopenie: de rol van hormonale factoren en lichamelijke activiteit
05 / 2000 - 05 / 2005
[OBJECTIVES:] The objectives of this project are three-fold: 1) to investigate whether sarcopenia is a risk factor for mobility limitations; 2) to investigate whether endocrine factors and physical activity are independently associated with sarcopenia; 3) to investigate whether endocrine factors and physical activity have synergistic effects on the prevention of sarcopenia. [METHODS:] The study objectives will be addressed in an epidemiological approach. Data from three selected studies will be used: the Longitudinal Aging Study Amsterdam, the Health, Aging and Body Composition Study and the Framingham Heart Study. All studies include accurate measurements of muscle mass by dual-energy X-ray absorptiometry. [RESULTS:] The cross-sectional relationship of two pro-inflammatory cytokines, interleukin-6 and tumor necrosis factor-a, with muscle mass and muscle strength was investigated among 3075 black and white men and women aged 70-79 years, participants of the Health, Aging and Body Composition Study. Except for white men, persons with a high cytokine status had a 1.9-4.1% smaller appendicular skeletal muscle mass, a 3.3-6.5% smaller mid-thigh muscle area, a 7.5-10.8% lower grip strength and a 5.5-8.8% lower knee extensor strength, compared to those with a low cytokine status. These results suggest that higher cytokine levels, as often observed in healhy older persons, may contribute to the loss of muscle mass and muscle strength that accompanies aging. The prospective data of 1008 men and women aged 55-85 years, participants in the Longitudinal Aging Study Amsterdam, were used to test the hypothesis that elevated parathyroid (PTH) hormone concentration and low serum vitamin D (VitD) status were associated with a greater loss of grip strength and greater loss of appendicular skeletal muscle mass during a 3-year follow-up. Persons with low or intermediate VitD were 2.8 and 2.4 times more likely to lose >3% muscle mass than those with high VitD. Persons with a high PTH were more likely to lose >3% muscle mass (odds ratio = 2.3) and more likely to lose >40% grip strength (odds ratio = 1.7). Both studies show that biological factors may influence muscle mass and muscle strength, independent of health status and life-style factors, including physical activity. Data from the Health, Aging and Body Composition Study was also used to examine the one and two-year change in appendicular skeletal muscle mass using dual-energy X-ray absorptiometry. The mean change was 1-2%, with a high inter-person variability. Loss of appendicular skeletal muscle mass was greater in men than in women, and greater in blacks than in whites, suggesting that men and black people may be at a greater risk for sarcopenia.