Objective

Several studies have documented the protective effects of obesity on mortality and morbidity in patients undergoing cardiac surgery. The evidence base for this obesity paradox in cardiac surgery remains unclear, being considered an artifact due to population selection bias. The present systematic review sought to determine the effects of obesity on mortality and morbidity in the cardiac surgery setting.

Methods

A literature search was conducted using PUBMED, Medline, Embase, Scopus and Cochrane Central register from inception through June 30, 2015. Obesity was defined according to WHO (World Health Organisation) classification as body mass index ≥30 Kg/m2. Studies reporting the 30-day/in-hospital mortality and postoperative outcomes in obese and non-obese patients following cardiac surgery were identified. Three reviewers independently assessed studies for inclusions and performed data extraction.

Results

Sixty-eight cohort studies were included, comprising 357, 591 patients. Obese patients had lower 30-day/in-hospital mortality compared with their non-obese counterparts (OR 0.91, 95%CI 0.87-0.94). Obese patients had significantly lower stroke and re-operation for bleeding rates (OR 0.73, 95%CI 0.59-0.89 and 0.59, 95%CI 0.48-0.72, respectively), but higher risk of deep sternal wound infection (OR 1.55, 95%CI 1.24-1.92). No differences were observed with respect to length of hospital stay.

Conclusion

The present meta-analysis demonstrated that following cardiac surgery obesity was protective against 30-day/in-hospital mortality, stroke and re-operation for bleeding. The present data confirms the existence of an obesity paradox also in cardiac surgery, underlying the need for further investigation to identify the potential explanatory mechanisms.