The Association Between Obesity Class and Cause-Specific Mortality by Age and Sex in US Adults.

To investigate differences in cause-specific mortality risks between obesity classes stratified by age and sex, using a nationally representative sample of the US population. Differences in mortality risk by standard body mass index (BMI) categories with examination of Obesity Classes I-III, stratified by age (less or more than 65 years) and sex were examined using Cox proportional hazard ratios with data from NHANES Continuous (1999-2018) with mortality follow-up through 31 December 2019. Among younger adults (< 65 years), Obesity Class III was associated with higher all-cause, cardiovascular, non-cardiovascular/non-cancer and diabetes-related mortality compared to Class I. Among older adults (≥ 65 years), there were fewer significant associations with only cardiovascular and diabetes-related mortality risks being elevated in men with Obesity Class III and none in women. There were no differences in mortality risks between Obesity Classes I and II, except for diabetes-related mortality in younger adults and older men. Obesity Class III is strongly associated with higher mortality risk in younger adults (< 65 years) and to a lesser degree in older adults (≥ 65 years). Mortality risks were generally similar between obesity Classes I and II. Therefore, younger adults under 65 years of age with severe obesity may benefit more from aggressive obesity management.