Obesity, health status, and 7-year mortality in percutaneous coronary intervention: in search of an explanation for the obesity paradox.

Background: Obesity is a growing health problem and is associated with adverse outcomes in coronary artery disease (CAD). However, recent studies have shown better survival in cardiovascular patients with overweight or obesity, which has been referred to as the "obesity paradox". As there is no clear understanding of the phenomenon, we examined the association between body mass index (BMI) and all-cause mortality in patients treated with percutaneous coronary intervention (PCI) at 7-year follow-up, and the potential role of health status in explaining the obesity paradox.

Methods: Consecutive PCI patients (72.5% men; mean age 62.0 ± 11.2 years, range [27-90]years) from the Rapamycin-Eluting Stent Evaluated at Rotterdam Cardiology Hospital (RESEARCH) registry completed the 36-item short-form health survey (SF-36) to assess health status at baseline. Patients were classified into a normal weight, overweight or obesity group.

Results: The prevalence of normal weight was 34.7% (354/1019), overweight was seen in 45.9% (468/1019) of patients, and 19.3% (197/1019) was obese. After a median follow-up of 7.0 ± 1.7 years, 163 deaths (16.0%) from any cause were recorded. Cumulative hazard functions differed significantly for the obese and overweight group when compared to the normal weight group (log-rank X(2)=6.59, p<0.05). In multivariable analysis, overweight, but not obesity, remained associated with a lower risk for all-cause mortality (HR=0.60, 95%CI [0.42-0.86], p=0.005). Additionally, after adding the 8 health status SF-36 domains to the multivariate model, the association between overweight and mortality remained unchanged.

Conclusion: In our study population overweight, but not obesity, was associated with a lower risk for 7-year mortality in PCI patients. Health status as measured with the SF-36 did not seem to play a role in explaining the obesity paradox.