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.