Waist-to-hip ratio and body mass index as risk factors for cardiovascular events in CKD

Background: The role of obesity as a risk factor for cardiovascular disease in patients with chronic kidney disease (CKD) is poorly understood. Waist-to-hip ratio (WHR) is less influenced by muscle and bone mass than body mass index (BMI). We compared WHIR and BMI as risk factors for cardiac events (myocardial infarction and fatal coronary disease) in persons with CKD. Study Design: Cohort study. Setting & Participants: Persons with CKD, defined as baseline estimated glomerular filtration rate of 15 to 60 mL/min/1.73 m(2), drawn from 2 community studies: the Atherosclerosis Risk in Communities Study and the Cardiovascular Health Study. Predictor: WHR, waist circumference, and BMI. Outcomes & Measurements: Myocardial infarction and fatal coronary heart disease. Results: Of 1,669 participants with CKD, mean age was 70.3 years and 56% were women. Mean (SD) WHRs were 0.97 +/- 0.08 in men and 0.90 +/- 0.07 in women; mean (SD) BMI was 27.2 +/- 4.6 kg/m(2). During a mean of 9.3 years of follow-up, there were 334 cardiac events. In multivariable-adjusted Cox models, the highest WHR group (n = 386) was associated with an increased risk of cardiac events compared with the lowest WHR group (hazard ratio, 1.36; 95% confidence interval, 1.01 to 1.83). Obesity, defined as BMI greater than 30 kg/m(2) (n = 381), was not associated with cardiac events (hazard ratio, 0.86; 95% confidence interval, 0.62 to 1.20) in comparison to participants with normal BMI (<25 kg/m(2)). Results with waist circumference were similar to those with BMI. Limitations: Absence of a gold standard for measurement of visceral fat. Conclusions: WHR, but not BMI, is associated with cardiac events in persons with CKD. Relying exclusively on BMI may underestimate the importance of obesity as a cardiovascular disease risk factor in persons with CKD.