Influence of body mass index on mortality after surgery for perforated peptic ulcer

Background: Body mass index (BMI) is a strong predictor of mortality in the general population. In spite of the medical hazards of obesity, a protective effect on mortality has been suggested in surgical patients: the obesity paradox. The aim of the present nationwide cohort study was to examine the association between BMI and mortality in patients treated surgically for perforated peptic ulcer (PPU). Methods: This was a national prospective cohort study of all Danish patients treated surgically for PPU between 1 February 2003 and 31 August 2009, for whom BMI was registered. Non-surgically treated patients and those with malignant ulcers were excluded. The primary outcome measure was 90-day mortality. The association between BMI and mortality was calculated as crude and adjusted relative risks (RRs) with 95 per cent confidence intervals (c.i.). Results: Of 2668 patients who underwent surgical treatment for PPU, 1699 (63.7 per cent) had BMI recorded. Median age was 69.4 (range 17.6-100.9) years and 53.7 per cent of the patients were women. Some 1126 patients (66.3 per cent) had at least one of six co-morbid diseases; 728 (42.8 per cent) had an American Society of Anesthesiologists grade of III or more. A total of 471 patients (27.7 per cent) died within 90 days of surgery. Being underweight was associated with a more than twofold increased risk of death following surgery for PPU (adjusted RR 2.26, 95 per cent c.i. 1.37 to 3.71). No statistically significant association was found between obesity and mortality. Conclusion: Being underweight was associated with increased mortality in patients with PPU, whereas being overweight or obese was neither protective nor an adverse prognostic factor.