Metabolic health status and the obesity paradox in older adults

Authors: CHENG, F - Pennsylvania State University; GAO, X - Pennsylvania State University; MITCHELL, D - Pennsylvania State University; WOOD, C - Geisinger Medical Center; ROLSTON, D - Geisinger Medical Center; STILL, C - Geisinger Medical Center; JENSEN, G - University Of Vermont College Of Medicine

Submitted to: Journal of Nutrition in Gerontology and Geriatrics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/1/2016
Publication Date: 8/25/2016
Citation: Cheng, F.W., Gao, X., Mitchell, D.C., Wood, C., Rolston, D.D., Still, C.D., Jensen, G.L. 2016. Metabolic health status and the obesity paradox in older adults. Journal of Nutrition in Gerontology and Geriatrics. 35(3):161-176.

Interpretive Summary: The association between metabolic health and all-cause mortality has been documented among middle-aged adults; however this approach has not yet been well validated for older persons. This study found that metabolic health status significantly modifies the association between body mass index and mortality of older persons. Compared to metabolically healthy with body mass index in the normal range of 18.5–24.9, the metabolically healthy who were overweight or obesity did not have significantly greater risk of all-cause mortality independent of age, sex, smoking, alcohol, laboratories, and comorbidity. These findings suggest that the “obesity paradox” described in previous studies may be partially explained by the inclusion of metabolically healthy overweight and obese persons who do not have an elevated mortality risk.

Technical Abstract: The explanation for reduced mortality among older persons with overweight or class I obesity compared to those of desirable weight remains unclear. Our objective was to investigate the joint effects of body mass index (BMI) and metabolic health status on all-cause mortality in a cohort of advanced age. Adults aged 74 ± 4.7 (mean ± SD) years at baseline (n=4551) were categorized according to BMI (18.5-24.9, 25.0-29.9, 30.0-34.9, and =35.0 kg/m2) and the presence or absence of a metabolically healthy phenotype (i.e., 0 or 1 risk factors based on a modified Adult Treatment Panel III). Metabolically unhealthy was = 2 risk factors. There were 2294 deaths over a mean 10.9 years of follow up. Relative to metabolically healthy desirable weight, metabolically healthy overweight or class I obesity was not associated with a greater mortality risk (HR 0.90; 95CI% 0.73-1.13 and HR 0.58; 95CI% 0.42-0.80, respectively) (P-interaction < 0.001). Results remained consistent in rigorous sensitivity analyses. The “obesity paradox” may be partially explained by the inclusion of metabolically healthy overweight and obese older persons, who do not have elevated mortality risk, in population studies of BMI and mortality.