Body mass index and mortality in institutionalized elderly

Malnutrition and sarcopenia in institutions are very common and significantly affect the prognosis. Aging is characterized by weight and lean body mass losses. Accordingly, in elderly patients, body mass index (BMI) is considered a marker of protein stores rather than of adiposity. Current guidelines suggest a BMI 21 kg/m(2) or lower as major trigger for nutritional support. We evaluated the association between BMI and mortality in institutionalized elderly.

This was a multicentric prospective cohort study involving 519 long-term care resident elderly individuals. Risk for mortality across BMI tertiles was estimated by the Cox hazards regression model adjusted for potential confounders recorded at inclusion and collected during the follow-up.

During a median follow-up of 5.7 years (25th to 75th percentile, 5.2-8.2], 409 (78.8%) elderly patients died. In primary analyses, based on variables collected at inclusion, patients in the first tertile of BMI (≤ 21 kg/m(2)) were at higher risk for all-cause (hazard ratio [HR] 1.38; 95% confidence interval [CI] 1.04-1.84; P = .025) and cardiovascular mortality (HR = 1.49; 95% CI, 1.00-2.08; P = .045). Increased risk was confirmed even after adjusting for nutritional support during the follow-up (all-cause HR = 1.53; 95% CI, 1.13-2.06; P = .006; cardiovascular HR = 1.62; 95% CI, 1.09-2.40; P = .018), which in turn was associated with a reduced risk (all-cause HR = 0.74; 95% CI, 0.55-0.97; P = .035; cardiovascular HR = 0.62; 95% CI, 0.42-0.91; P = .016).

BMI is significantly associated with all-cause and cardiovascular mortality in institutionalized elderly patients. A value of 21 kg/m(2) or lower can be considered a useful trigger for nutritional support. These results support intending BMI as nutritional reserve in institutionalized elderly patients.