BACKGROUND: Obesity rates have increased sharply in recent decades. As there is a growing number of cases in which acute pancreatitis (AP) is accompanied by obesity, we found it clinically relevant to investigate how body-mass index (BMI) affects the outcome of the disease. AIM: To quantify the association between subgroups of BMI and the severity and mortality of AP. METHODS: A meta-analysis was performed using the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) Protocols. Three databases (PubMed, EMBASE and the Cochrane Library) were searched for articles containing data on BMI, disease severity and mortality rate for AP. Englishlanguage studies from inception to 19 June 2017 were checked against our predetermined eligibility criteria. The included articles reported all AP cases with no restriction on the etiology of the disease. Only studies that classified AP cases according to the Atlanta Criteria were involved in the severity analyses. Odds ratios (OR) and mean differences (MD) were pooled using the random effects model with the DerSimonian-Laird estimation and displayed on forest plots. The meta-analysis was registered in PROSPERO under number CRD42017077890. RESULTS: A total of 19 articles were included in our meta-analysis containing data on 9997 patients. As regards severity, a subgroup analysis showed a direct association between AP severity and BMI. BMI < 18.5 had no significant effect on severity; however, BMI > 25 had an almost three-fold increased risk for severe AP in comparison to normal BMI (OR = 2.87, 95%CI: 1.90-4.35, P < 0.001). Importantly, the mean BMI of patients with severe AP is higher than that of the non-severe group (MD = 1.79, 95%CI: 0.89-2.70, P < 0.001). As regards mortality, death rates among AP patients are the highest in the underweight and obese subgroups. A BMI < 18.5 carries an almost two-fold increase in risk of mortality compared to normal BMI (OR = 1.82, 95%CI: 1.32-2.50, P < 0.001). However, the chance of mortality is almost equal in the normal BMI and BMI 25-30 subgroups. A BMI > 30 results in a three times higher risk of mortality in comparison to a BMI < 30 (OR = 2.89, 95%CI: 1.10-7.36, P = 0.026). CONCLUSION: Our findings confirm that a BMI above 25 increases the risk of severe AP, while a BMI > 30 raises the risk of mortality. A BMI < 18.5 carries an almost two times higher risk of mortality in AP.
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