Background: Obesity is a leading risk factor for increased mortality. However, it remains unclear how this relationship varies across different age groups.
Objectives: To evaluate whether the associations between adiposity and mortality are modified by age in a nationally representative sample of U.S. adults.
Methods: We analyzed data from 44,041 U.S. adults aged 18-79 years from the National Health and Nutrition Examination Survey (1999-2018), linked to mortality data through 2019. Anthropometric measures included body mass index (BMI), waist circumference (WC), weight, and waist-to-height ratio (WHtR). Cox proportional hazards models were used to assess the interaction between age and adiposity on all-cause and cardiovascular mortality, adjusting for demographic, behavioral, and clinical covariates.
Results: Over a median follow-up of 10.1 years, there were 5,019 deaths (1,186 cardiovascular). Significant interactions between age and all four adiposity measures were observed (p < 0.05). Associations between adiposity and mortality were strongest among younger adults. For example, each 1-SD increase in BMI was associated with a cardiovascular mortality hazard ratio (HR) of 1.49 (95% CI: 1.27-1.77) in adults aged 18-49, versus 1.15 (95% CI: 0.99-1.32) in those aged 70-79. Class 3 obesity was associated with a cardiovascular mortality HR of 4.37 (95% CI: 2.01-9.50) in younger adults. Underweight status was also associated with elevated all-cause mortality, particularly among younger individuals (HR: 2.04; 95% CI: 1.24-3.36).
Conclusions: Age significantly modifies the relationship between adiposity and mortality. Younger adults experience greater mortality risks from both obesity and underweight, underscoring the need for early, age-tailored interventions).
JACC: Advances Editor-in-Chief
Candice K. Silversides, MD, FACC
JACC: Advances CME Editor
Kenneth A. Ellenbogen, MD
Author
Harlan Krumholz, MD
Important Dates
Date of Release: December 24, 2025
Term of Approval/Date of CME/MOC Expiration: December 23, 2026