RELATIONSHIP OF BODY-MASS INDEX TO SUBSEQUENT MORTALITY AMONG SERIOUSLY ILL HOSPITALIZED-PATIENTS

Objective: To determine if body mass Index (BMI = weight [kg]/height [ m](2)), predictive of mortality in longitudinal epidemiologic studies, was also predictive of mortality in a sample of seriously ill hospita lized subjects. Design: Prospective, multicenter study. Setting: Five tertiary care medical centers in the United States. Patients: Patients greater than or equal to 18 yrs of age who had one of nine illnesses of sufficient severity to anticipate a B-month mortality rate of 50% w ere enrolled at five participating sites in the Study to Understand Pr ognoses and Preferences for Outcomes and Risks of Treatments (SUPPORT) . Interventions: None. Measurements and Main Results: Patients were as ked their current height and weight as part of the demographic data. S tratifying body mass index by percentile rank (less than or equal to 1 5, 15 to 85, and greater than or equal to 85th percentiles), risk rati os for mortality were calculated by Cox Proportional Hazards using the 15th to 85th percentile of body mass index as the reference group whi le controlling for multiple variables such as prior weight loss, album in, and Acute Physiology Score. A body mass index in the less than or equal to 15th percentile was associated with an excess risk of mortali ty (risk ratio =1.23; p<.001)within 6 months. High body mass index (gr eater than or equal to 85th percentile) was not significantly related to risk of mortality. Conclusions: Body mass index, a simple anthropom etric measure of nutrition employed in community epidemiologic studies , has now been demonstrated to be a predictor of mortality in an acute ly ill population of adults at five different tertiary centers. Even w hen controlling for multiple disease states and physiologic variables and removing from the analysis all patients with significant prior wei ght loss, a body mass index below the 15th percentile remained a signi ficant and independent predictor of mortality. Examination of patient vs. proxy data did not change the results. Future studies examining va riables predictive of mortality should include body mass index, even i n acutely ill populations with a poor probability of survival.