Normal weight obesity and mortality in United States subjects ≥60 years of age (from the Third National Health and Nutrition Examination Survey)

Abstract

Current body mass index (BMI) strata likely misrepresent the accuracy of true adiposity in older adults. Subjects with normal BMI with elevated body fat may metabolically have higher cardiovascular and overall mortality than previously suspected. We identified 4,489 subjects aged ≥60 years (BMI = 18.5 to 25 kg/m(2)) with anthropometric and bioelectrical impedance measurements from the National Health and Nutrition Examination Surveys III (1988 to 1994) and mortality data linked to the National Death Index. Normal weight obesity (NWO) was classified in 2 ways: creation of tertiles with highest percentage of body fat and body fat percent cutoffs (men >25% and women >35%). We compared overall and cardiovascular mortality rates, models adjusted for age, gender, smoking, race, diabetes, and BMI. The final sample included 1,528 subjects, mean age was 70 years, median (interquartile range) follow-up was 12.9 years (range 7.5 to 15.3) with 902 deaths (46.5% cardiovascular). Prevalence of NWO was 27.9% and 21.4% in men and 20.4% and 31.3% in women using tertiles and cutoffs, respectively. Subjects with NWO had higher rates of abnormal cardiovascular risk factors. Lean mass decreased, whereas leptin increased with increasing tertile. There were no gender-specific differences in overall mortality. Short-term mortality (<140 person-months) was higher in women, whereas long-term mortality (>140 person-months) was higher in men. We highlight the importance of considering body fat in gender-specific risk stratification in older adults with normal weight. In conclusion, NWO in older adults is associated with cardiometabolic dysregulation and is a risk for cardiovascular mortality independent of BMI and central fat distribution.