Is there a relationship between fat-free soft tissue mass and low cognitive function?: Results from a study of 7,105 women

OBJECTIVES: To test the hypothesis that low fat-free soft tissue mass and cognitive impairment are independently associated. DESIGN: Cross-sectional study. SETTING: Five geographic areas of France. PARTICIPANTS: Seven thousand one hundred five community-dwelling women aged 75 and older recruited from electoral rolls between 1992 and 1994. MEASUREMENTS: Fat-free soft tissue mass, body fat mass, and bone mineral density were measured using dual-energy x-ray absorptiometry. Study participants were assessed for cognitive impairment using the Short Portable Mental Status Questionnaire and divided into two groups according to their scores. Logistic regression models were used to calculate multivariate-adjusted differences in body composition between two groups of subjects according to their cognitive function. RESULTS: After adjustment for confounders, compared with women in the highest quartile of fat-free soft tissue mass, women in the lowest quartile had an odds ratio of 1.43 (95% confidence interval (CI) 1.07-1.91) for cognitive impairment. Low fat mass was also associated with lower cognitive function, with an odds ratio of 1.35 (95% CI 1.01-1.79) for the lower quartile of fat mass compared with the highest quartile. There was no association between cognitive impairment and bone mineral density. CONCLUSIONS: This finding supports the hypothesis that low muscle mass is associated with cognitive impairment in older women. These two components represent major causes of frailty and functional decline in older people and could have some common mechanisms. Nevertheless, these results do not predict the causal variable.