Background Body composition changes resulting from ageing (decreased muscle mass and increased fat tissue) are frequently not accompanied by concomitant changes in body mass index (BMI). Thus, BMI has low accuracy to estimate death risk attributed to changes in body composition in the older adults1. Currently, the best method for body composition analysis in routine clinical practice is dual energy X-ray absorptiometry (DXA)2. However, the few studies on body composition by DXA and mortality risk in elderly have some limitations, such as analysis not compartmentalized (subcutaneous and visceral tissues) of body fat and appendicular muscle mass not adjusted for fat mass3.
Objectives We sought to investigate the association between body composition by DXA (including visceral fat measurement) and mortality in a longitudinal, prospective, population-based cohort of elderly subjects.
Methods 839 community-dwelling subjects (516 women, 323 men), ≥65 years, were assessed by questionnaire on clinical data, laboratory exams and body composition by DXA using Hologic QDR 4500A equipment. DXA APEX software computes visceral adipose tissue (VAT) by subtracting the subcutaneous adipose tissue (SAT) from the total android fat. All analyses were performed at baseline. Total body fat was expressed by fat mass index (FMI) [(total body fat (kg)/height2 (m)]. Sarcopenia was defined as low appendicular muscle mass adjusted for fat. Mortality was recorded during 4 year-follow-up. Multivariate logistic regression was used to compute odds ratios for all-cause and cardiovascular mortality.
Results Over a mean 4.06±1.07 years of follow-up, there were 132 (15.7%) deaths. In men, after adjustment for age, BMI, smoking, physical activity, alcohol, diabetes, dyslipidemia, cardiovascular event, recurrent falls, 25OHD and PTH, the presence of sarcopenia (OR 11.36, 95% CI: 2.21–58.37, p=0.004) and visceral fat mass (OR 1.99 95% CI: 1.38–2.87, p<0.001, for each 100g-increase) significantly increased all-cause mortality risk, while FMI was associated with decreased mortality risk (OR 0.48, 95% CI: 0.33–0.71, p<0.001). Similar results were observed for cardiovascular mortality in men: sarcopenia (OR 14.84, 95% CI: 5.15–47.72, p<0.001), visceral fat mass (OR 1.66, 95% CI: 1.31–2.10, p<0.001) and FMI (OR 0.57,95% CI: 0.43–0.76, p<0.001). In women, only sarcopenia was predictor of all-cause (OR 62.88, 95% CI: 22.59–175.0, p<0.001) and cardiovascular death (OR 74.54, 95% CI: 9.72–571.46, p<0.001).
Conclusions Sarcopenia and fat distribution are associated with all cause and cardiovascular mortality risk in elderly, and they are different according to sex. Visceral fat and subcutaneous fat have opposite roles on mortality risk in elderly men, and this is distinct from what is observed in young adults.These findings point to the risk of encouraging weight loss in the elderly aiming young adult goals. Furthermore, DXA seems to be a promising tool for evaluation risk of mortality in elderly, since it is easily applicable in clinical practice.
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Disclosure of Interest None declared