Risk of increased mortality in underweight survivors: A brief report from the Childhood Cancer Survivor Study

Background Approximately 1 in 10 adult survivors of childhood cancer is underweight. Although the consequences of being overweight or obese have been well described, outcomes among childhood cancer survivors who are underweight are unknown. Objective To determine whether underweight status increases the risk of mortality. Procedure Cohort study: Marginal models with generalized estimating equations to evaluate the associations between body mass index (BMI), serious or life‐threatening chronic conditions, and death in the setting of long‐term follow‐up questionnaires and National Death Index search. Participants: Childhood cancer five‐year survivors diagnosed during 1970–1986 in the Childhood Cancer Survivor Study Exposure: Underweight status, defined as body mass index (BMI) < 18.5 kg/m2 compared with ideal body weight. Based on available literature on body weight and mortality from the general population, ideal body weight was defined as BMI 22.0‐24.9 kg/m2. Main outcomes: Overall mortality and cancer‐specific mortality. Results Of 9454 survivors (median age 35 years old (range, 17‐58), an average of 17.5 years from diagnosis), 627 (6.6%) participants were underweight at baseline or follow‐up questionnaire. Of 184 deaths, 29 were among underweight survivors. Underweight status was more common among females (9.1% vs. 4.5%, p