Low BMI and Weight Loss Both Impact 6-Month Nursing Home Mortality

Abstract

A low body mass index (BMI) and weight loss greater than 5 kg in the past year were both independent and “equally relevant” risk factors for the 6-month mortality of nursing home residents in a large international cross-sectional survey. And when both were present, the mortality risk was disproportionately increased. “On the basis of previous interventional trials [showing beneficial effects of oral nutritional supplements] and these observational data, any weight loss in nursing home residents, even if small, should be avoided to the greatest extent possible, as long as nutritional therapy is considered to be useful and without harm,” reported Rainer Wirth, MD, PhD, of the department of internal medicine and geriatrics at St. Marien-Hospital Borken, Germany, and his colleagues. “Residents with a low BMI and weight loss should receive particular attention and nutritional care as soon as weight loss occurs,” they added (Clin Nutr 2016;35:900–6). These findings come from the “nutritionDay” project in which nursing homes and hospital wards around the world have volunteered to participate in an annual one-day cross sectional survey, or audit, of nutritional status (http://www.nutritionday.org). Dr. Wirth and his coinvestigators analyzed data collected from 2007–2012 on 10,298 residents of 191 nursing homes in 13 Western developed countries, including the United States. Their questionnaires asked whether weight loss was present in the last year and what was the amount of weight loss per defined categories (1–5 kg, 5–15 kg, and >15 kg). The answers were combined to focus on weight loss greater than 5 kg. A BMI of less than 20 kg/m2 was defined as relevantly low for older individuals in concordance with definitions in the nutrition guidelines of the European Society for Clinical Nutrition and Metabolism. Approximately 18% of residents had a BMI below 20 kg/m2, and 11% had lost more than 5 kg in the previous year. These residents were at least 65 years old and had a mean age of 85. A low BMI and greater than a 5-kg weight loss were both independent and significant risk factors for 6-month mortality. In residents with weight loss greater than 5 kg and a BMI greater than 20 kg/m2, mortality was 17.4%, and in those without such weight loss but with a low BMI, mortality was 19.8%. When both features were present, mortality increased disproportionately to 35.7%, which suggests an interaction between BMI and weight loss, the investigators wrote. There was a strong dose–effect relationship between each feature and mortality, they noted. Weight loss and low BMI are both well-known risk factors for poor outcomes in the older population, but “their nature is substantially different,” they wrote. Weight loss is “predominantly associated with disease and frailty,” whereas a low BMI “might be a permanent characteristic of a person or a consequence of previous weight loss.” Previous studies did not specify whether individuals with a low BMI also had recent weight loss — and thus it was unclear whether it was primarily the low BMI that had increased the mortality risk or whether the main source of risk was the unknown weight loss, the authors said. The nutritionDay study allowed for the analysis of both risk factors in one data set. Weight loss of less than 5 kg was significantly more prevalent in the group with a low BMI compared with those with a higher BMI, but the association between BMI and mortality remained after adjusting for weight loss. “There’s no doubt that a low BMI, per se, is as predictive for mortality as weight loss,” Dr. Wirth and his associates wrote. Christine Kilgore is a freelance writer in Falls Church, VA.