Trends and seasonality in biliary and alcoholic acute pancreatitis incidence in the United States

Abstract

Background: The incidence of acute pancreatitis (AP) has increased over the last decade in the United States (US). The seasonal variation in the incidence of certain cardiovascular and acute surgical pathologies, including AP has been well established. However, differences between biliary and alcoholic AP remain to be elucidated. We aim to describe seasonality and trends of biliary and alcoholic AP incidence, morbidity and mortality in the US. Methods: The study population included 658,000 in-hospital admissions for primary diagnosis of AP (AHRQ NIS, 2000-2012). Biliary and alcoholic etiologies were differentiated by diagnostic and procedural ICD codes. Seasonal trend decomposition analyses using LOESS was performed. Results: We detected a steady linear trend of alcoholic AP with 1.5-fold increase in incidence over a 12-year span. An incremental increase of biliary AP abated around 2003. Every year we observed a peak in AP admissions in July-August, which was more distinct for alcohol etiology, which was independent of state average temperature. Incidence of biliary AP across the country and AP in states with low alcohol consumption also exhibited a warm seasonal surge with a secondary peak in January. At the same time, the lowest mortality and length of in- hospital stay occurred during the warmer season. In addition, mortality decreased 3-fold and the average length of stay 1.3-fold in 12-year span. The highest morbidity occurred in December-January. Conclusion: In the US, there was an increasing trend in AP incidence, which is predominantly associated with alcohol use. The warm season is characterized by a marked increase in AP incidence but with reduced morbidity and mortality. These findings may prove useful for hospital and staffing allocation, and for diagnosis and prognosis.