Worldwide Seasonal Variation in Hospital Admissions for Diverticulitis

Importance: Seasonal or climate variation is increasingly recognized as being associated with the incidence of several acute abdominal conditions, yet its role in diverticulitis remains uncertain. Understanding temporal trends may provide insight into modifiable environmental or behavioral risk factors and guide health system preparedness. Objective: To systematically review published evidence examining the presence, magnitude, and direction of seasonal variation in diverticulitis incidence or hospital admissions worldwide. Evidence Review: A systematic search of PubMed, Embase, Web of Science, and Google Scholar was conducted using combinations of the terms diverticulitis, diverticular disease, and seasonal variation. Eligible studies included original, peer-reviewed human research reporting temporal or seasonal patterns of diverticulitis. Data were extracted on study design, region, sample size, analytic method, and reported seasonal peaks and troughs. Given heterogeneity, findings were synthesized qualitatively. Findings: Eight observational studies met inclusion criteria, totaling 1 104 640 diverticulitis cases across 4 continents from 1997 through 2019. Seven studies reported a winter trough, a summer or autumn peak, and a typical peak-to-trough amplitude of 16% to 27%. A single small series reported a winter peak. The multicountry analysis demonstrated phase reversal between hemispheres, confirming true seasonality. Proposed mechanisms included dehydration, dietary change, microbial and immune modulation, and vitamin D exposure. No study found significant seasonal variation in disease severity. Conclusions and Relevance: This systematic review found that diverticulitis exhibits a reproducible seasonal pattern, more commonly peaking in warmer months and with consistent phase reversal between hemispheres. The findings suggest environmental or behavioral triggers rather than random variation. Future prospective studies integrating patient-level exposures are needed to clarify mechanisms and identify preventive strategies.