Validation of the obesity paradox by body mass index and waist circumference in patients undergoing percutaneous coronary intervention.

Abstract

The paradoxical association of obesity with mortality, named the "obesity paradox", has been inconsistent, possibly due to a difference between body mass index (BMI) and central obesity, estimated by waist circumference (WC) as patterns of adiposity. We enrolled 8513 participants from the Kumamoto Intervention Conference Study, a multicenter registry that included consecutive patients undergoing percutaneous coronary intervention (PCI) at 18 centers between 2008 and 2017 in Japan. Patients were divided into quartiles in ascending order of the BMI or WC. The primary endpoints were all-cause mortality and cardiovascular death within a year. There were 186 deaths (case fatality rate, 22.1/1000 person-years) during the follow-up period. The lowest group (1st quartile) of BMI or WC had the worst prognosis among the quartiles (1st quartile, 4.2%; 2nd quartile, 1.9%; 3rd quartile, 1.5%; 4th quartile, 1.1%; P < 0.001 (χ²) and 1st quartile, 4.1%; 2nd quartile, 2.3%; 3rd quartile, 1.2%; 4th quartile, 1.5%; P < 0.001 (χ²), respectively). Similar results were obtained for cardiovascular death. In a multivariable analysis adjusted by nine conventional factors, the lowest group (1st quartile) of BMI (hazards ratio, 2.748; 95% confidence interval [CI], 1.712-4.411) and WC (hazards ratio, 2.340; 95% CI, 1.525-3.589) were independent prognostic factors for all-cause mortality. By dividing the participants into two groups according to either the BMI or WC based on the National Cholesterol Education Program Adult Treatment Panel III and World Health Organization classification, the highest mortality was observed in the lower group. However, the C-statistic after adding BMI (quartile) to conventional factors was found to be slightly higher than BMI (two categories) and WC (two categories) (0.735 vs. 0.734). The obesity paradox was observed in patients after PCI, and single-use of BMI (or WC) was sufficient to predict the prognosis of patients after PCI.