Separate and Combined Associations of Body-Mass Index and Abdominal Adiposity With Cardiovascular Disease: Collaborative Analysis of 58 Prospective Studies
Do body mass index (BMI), waist circumference, and waist-to-hip ratio predict first cardiovascular disease effects when used in combination with other risk factors?
Records from 58 cohorts were included in this analysis. Hazard ratios (HRs) were calculated for 1 standard deviation (SD) higher baseline values (4.56 kg/m2 higher BMI, 12.6 cm higher waist circumference, and 0.083 higher waist-to-hip ratio) and measures of risk discrimination and reclassification. Serial adiposity assessments were used to calculate regression dilution ratios.
Records from a total of 221,934 people residing in 17 countries were included in this analysis. A total of 14,297 incident cardiovascular disease outcomes occurred during follow-up. Serial assessments of adiposity had been completed in approximately 63,821 people (mean interval of assessment was 5.7 years [SD 3.9]). Among adults with a BMI of 20 kg/m2 or higher, HRs for cardiovascular disease were 1.23 (95% confidence interval [CI], 1.17-1.29) with BMI, 1.27 (95% CI, 1.20-1.33) with waist circumference, and 1.25 (95% CI, 1.19-1.31) with waist-to-hip ratio, after adjustment for age, sex, and smoking status. After further adjustment for baseline systolic blood pressure, history of diabetes, and total and high-density lipoprotein cholesterol, corresponding HRs were 1.07 (95% CI, 1.03-1.11) with BMI, 1.10 (95% CI, 1.05-1.14) with waist circumference, and 1.12 (95% CI, 1.08-1.15) with waist-to-hip ratio. Addition of information on BMI, waist circumference, or waist-to-hip ratio to a cardiovascular disease risk prediction model containing conventional risk factors did not significantly improve risk discrimination (C-index changes of -0.0001, 0.0001, and 0.0008, respectively). Re-classification of participants to categories of predicted 10-year risk was also not significant.
The investigators concluded that interpretation of BMI, waist circumference, and waist-to-hip ratio, whether assessed alone or in combination, do not significantly improve cardiovascular disease risk prediction in people in developed countries when additional information is available for systolic blood pressure, history of diabetes, and lipids.
This large-scale analysis demonstrates the predictive value of known cardiovascular risk factors. Inclusion of measures such as BMI may not add to prediction models; however, measures of adiposity including waist circumference and waist-to-hip ratio are clinically useful in that reducing adiposity often results in improvement of traditional risk factors.
Keywords: Follow-Up Studies, Lipids, Blood Pressure, Risk Factors, Cholesterol, Waist Circumference, Waist-Hip Ratio, Body Mass Index, Developed Countries, Cardiovascular Diseases, Obesity, Diabetes Mellitus
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