Background and aim: There is evidence for a J-shaped association between Body Mass Index (BMI) and all-cause mortality in general populations. In cardiac surgical patients, the effect of BMI on mortality and major adverse cardiac and cerebrovascular events (MACCE) is not completely clear.
Methods and results: We investigated the effect of BMI on MACCE (primary endpoint), as well as intensive care unit (ICU)-related outcomes and mid-term mortality in 9125 consecutive patients who were operated on at our institution between July 2009 and July 2012. Of the study cohort, 3.0% were underweight (BMI < 20 kg/m(2)), 28.0% had a normal BMI (20-24.99 kg/m(2)), 43.1% were overweight (BMI 25-29.99 kg/m(2)), 19.3% were obese (BMI 30-34.99 kg/m(2)), and 6.6% were severely obese (BMI ≥ 35 kg/m(2)). Compared with overweight patients (lowest incidence of MACCE), the multivariable-adjusted odds ratio of MACCE in severely obese patients was 1.39 (95% CI: 1.03-1.87). Underweight and severely obese patients had the longest risk-adjusted duration of mechanical ventilator support and ICU stay (P-values 0.004-0.001). The red blood cell concentrates requirement was highest in underweight patients (P < 0.001). Compared with normal and overweight patients, the multivariable-adjusted hazard ratio of 2-year mortality was higher in underweight patients (1.72 [95% CI: 1.26-2.36] and =2.07 [95% CI: 1.51-2.83], respectively), but did not differ significantly in severely obese patients.
Conclusion: Data demonstrate that both severe obesity and underweight are independent risk factors for operative complications in cardiac surgical patients. With respect to mid-term survival, special attention should be paid to underweight patients scheduled for cardiac surgery.
Keywords: Body mass index; Cardiac surgery; Major adverse cardiac and cerebrovascular events; Mortality; Survival.
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