Risk Factors for Low Muscle Mass in a Population-based Prospective Cohort of Brazilian Community-dwelling Older Women: The Sao Paulo Ageing & Health (SPAH) Study

Introduction: Sarcopenia is characterized by progressive loss of skeletal muscle mass, which results in decreased muscle strength, functional impairment, and increased risk of death. Few studies have performed a concomitant evaluation of clinical, laboratory, and body composition variables to accurately determine the contribution of each parameter to low muscle mass (LMM) in older subjects. This study aimed to identify risk factors (clinical, laboratory parameters, BMD, and body composition by DXA including visceral fat) for LMM in a prospective cohort of older Brazilian women. Methods: A total of 408 women aged >= 65 yr from the Sao Paulo Ageing & Health study were evaluated with clinical data, laboratory bone tests, BMD, and body composition by DXA using Hologic QDR 4500A equipment. Risk factors were measured at baseline (2005-2007). After a follow-up of 4.3 +/- 0.8 yr, subjects were classified according to the LMM definition of the Foundation for the National Institutes of Health criteria. LMM was defined when appendicular lean mass divided by body mass index was less than 0.512. Multivariate logistic regression models were used to identify independent risk factors for LMM. Results: At the end of follow-up, 116 women (28.4%) had LMM. Age averages were 73.3 +/- 4.9 yr in the LMM group and 72.5 +/- 4.5 yr in the normal group (p = 0.11). Mean BMI was 30.6 +/- 5.2 kg/m(2) in the LMM group and 28.1 +/- 4.7 kg/m(2) in the normal group (p < 0.001). In multivariate analyses, predictors of LMM were: falls (OR = 1.14, p = 0.016), TSH levels (OR = 1.08, p = 0.018, per 1 mu UI/L-increase), serum creatinine levels (OR =11.11, p < 0.001, per 1 mg/dL-decrease), and visceral adipose tissue (VAT) mass (OR = 1.17, p < 0.001, per 100 g increase). Conclusions: Falls, high TSH, low creatinine, and high VAT were risk factors for LMM in older women. More attention should be paid to these factors, since they are potentially reversible with adequate intervention.