Cyclical increase in diverticulitis during the summer months.

Objective: We hypothesized that the rate of nonelective hospital admissions for diverticulitis conforms to seasonal variation.

Design: Retrospective cohort analysis.

Setting: Patients admitted to hospitals in the Nationwide Inpatient Sample, a 20% sample of US community hospitals.

Patients: We identified patients with a nonelective admission or discharge for diverticulitis from January 1, 1997, through December 31, 2005, and determined the proportion of diverticulitis admissions (standardized to all inpatient admissions) for a particular admission month or discharge quarter. Next, we analyzed the potential effects of region, age, sex, and race on excess seasonal admissions for diverticulitis.

Results: On average, total nonelective admissions for diverticulitis were lowest in February (23 744 admissions) and highest in August (29 733 admissions), a 25.2% increase in cases. Similarly, diverticulitis discharges increased by 14.3% during the third quarter compared with the first (P < .001). A significant seasonal pattern of diverticulitis admissions was identified that conformed to a major sinusoidal component (P < .001). The excess seasonal burden of nonelective diverticulitis admissions in the third quarter was noted across US census regions, age, sex, and race.

Conclusions: Hospitalization for diverticulitis adheres to a sinusoidal pattern, with more nonelective admissions occurring during the summer months. The excess summer burden of diverticulitis is noted across US census regions, age, sex, and race. A more thorough understanding of these trends may provide a mechanism to identify a potential trigger for diverticulitis.