Abstract
BACKGROUND: Obesity is an established risk factor for cardiovascular disease (CVD); however, the overall and sex-specific relationships across the full spectrum of body mass index (BMI), particularly severe obesity defined as class 2 (BMI 35 to <40.0 kg/m2) and class 3 (BMI ≥40 kg/m2), and long-term CVD outcomes remain incompletely described.
METHODS: We included 289 875 participants (mean age, 60.3 years; 79.2% women) from 21 cohorts of the Cross-Cohort Collaboration enrolled between 1948 and 2015 with harmonized BMI data, a BMI ≥18.5 kg/m2, and at least one of nine adjudicated outcomes: time to first fatal and non-fatal myocardial infarction (MI), fatal and nonfatal stroke, heart failure (HF), atrial fibrillation (AF), total coronary heart disease (CHD), total CVD, CHD mortality, CVD mortality, and all-cause mortality. Multivariable Cox proportional hazard models with restricted cubic splines were used to estimate the hazard ratio (HR) of BMI for each outcome, adjusting for demographic and clinical risk factors.
RESULTS: Over 19.2 median years (25th, 11.6; 75th, 23.5 percentile) of follow-up, there were a total of 15 542 incident MI events, 15 467 incident stroke events, 14 172 incident HF events, 9066 diagnosed AF, and 113 918 total deaths, of which 14 647 were CHD-related and 28 879 were CVD-related. Overall, compared with individuals with normal weight, those with class 2 and class 3 obesity had the highest risk of HF (HR, 2.1, 95% CI, 2.0-2.3, and HR, 3.0, 95% CI, 2.7-3.2, respectively) and AF (HR, 1.8, 95% CI 1.7-2.0, and HR, 2.8, 95% CI, 2.5-3.1, respectively). Compared with men, women experienced higher relative increases in the risk associated with severe obesity for outcomes stroke, CVD, and all-cause mortality (P for interaction: <0.001, 0.003, and <0.001, respectively). Furthermore, in men, no increase in stroke risk was observed with higher BMI categories (P trend=0.49), whereas in women, the risk of stroke plateaued across obesity subclasses (compared with normal weight) yet remained significantly increased.
CONCLUSIONS: Higher BMI was robustly associated with increased risk for most outcomes, particularly HF and AF, even after adjusting for traditional risk factors. Observed sex differences in the relative hazard of higher BMI categories and stroke, total CVD, and all-cause mortality suggest potential differences in underlying biological mechanisms.