Objectives: The aim of this sudy was to investigate the presence of an obesity paradox on the long-term mortality of patients undergoing primary isolated coronary artery bypass surgery and to uncover whether any discrepancy found could be attributable to cardiovascular or noncardiovascular causes.
Methods: Retrospective analysis of 5242 consecutive patients with body mass index (BMI) over 18.5 kg/m2 undergoing primary isolated coronary artery bypass surgery, performed from 2000 to 2015, in a Portuguese level III Hospital. The primary end point was long-term all-cause mortality. Secondary outcomes were long-term cause-specific mortality (cardiovascular and noncardiovascular). We fitted overall, and cause-specific hazard models, with BMI forced both as a categorical (using World Health Organization predefined cutoffs) and as a continuous variable.
Results: Follow-up was 99.7% complete. The median follow-up time was 12.79 years (interquartile range, 9.51-16.61). The cumulative incidence functions failed to uncover any difference in 15-year all-cause (log-rank test, P = 0.400), cardiovascular (Gray's test, P = 0.996) and noncardiovascular mortality (Gray's test, P = 0.305) between BMI categories. Likewise, extensive multivariable-adjusted Cox regression and cause-specific hazards models failed to demonstrate in-between category differences, with BMI forced as a categorical variable. On the other hand, using BMI as a continuous variable, the model identified the optimal BMI as between 25.8 and 30.3 kg/m2 (nadir around 28.9 kg/m2), albeit this was dependent on the definition of the reference value.
Conclusions: In this longitudinal, population-level analysis of patients undergoing isolated primary coronary artery bypass grafting, we could not attest to any protective effect of obesity on long-term survival.
Keywords: Atherosclerosis; Coronary artery bypass surgery; Obesity; Survival analysis.
© The Author(s) 2023. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery.