Predictors of low bone mineral density in the elderly: the role of dietary intake, nutritional status and sarcopenia

OBJECTIVES: The aims of this study were to investigate the relationship between sarcopenia, dietary intake, nutritional indices and hip bone mineral density (BMD) in the elderly, and to estimate the risk of low BMD due to specific independent predictor thresholds. SUBJECTS AND METHODS: Body mass index (BMI), serum albumin, energy and protein intake were studied in 352 elderly outpatients (216 women aged 73.5+/-5.3 years and 136 men aged 73.9+/-5.6 years). BMD at different hip sites and appendicular skeletal muscle mass (ASMM) were assessed by dual-energy X-ray absorptiometry. RESULTS: The prevalence of osteoporosis was 13% in men and 45% in women, while the prevalence of sarcopenia (50%) and hypoalbuminemia (5%) were similar in both genders. BMI, albumin and ASMM were significantly associated with BMD in both genders: so was protein intake, but only in men. By multiple regression analysis, the variables that retained their independent explanatory role on total hip BMD, were BMI and protein intake in men, and BMI and albumin in women. By logistic regression analysis, men risked having a low BMD with a BMI <22 (OR=12) and a protein intake <65.7 g/day (OR=3.7). Women carried some risk already in the BMI 25-30 class (OR=5), and a much greater risk in the BMI <22 class (OR=26). Albumin <40 g/l also emerged as an independent risk factor (OR=2.6). CONCLUSIONS: BMI in both genders, albumin in women and protein intake in men have an independent effect on BMD. BMI values <22 are normal for younger adults but carry a higher risk of osteoporosis in the elderly, particularly in women. Age-related sarcopenia does not seem to be involved in bone mass loss.