BACKGROUND: Understanding disease seasonality can provide guidance for future biomedical research. OBJECTIVE: To examine whether meteorological factors and calendar months impact duodenal ulcer (DU) exacerbations. DESIGN: We conducted a retrospective time series analysis of population-based claims data. PARTICIPANTS: DU inpatients (1997-2003; all endoscopy confirmed) from Taiwan, a small island nation, n = 160,510. Inpatient admission was used as a proxy for exacerbation because 98.5% of cases had hemorrhage or perforation or both. MEASUREMENTS: We used multivariate autoregressive integrated moving average (ARIMA) modeling to examine if DU admissions/100,000 was associated with calendar month, ambient temperature, relative humidity, rainfall, atmospheric pressure, and sunshine hours, controlling for available DU-relevant comorbidities. RESULTS: DU admissions increased with age. ARIMA modeling showed a February (Chinese New Year-related) trough in all age groups (all p < 0.001; adjusted for meteorological variables and comorbidities), consistent with a February dip in all-cause admissions. Among 35-49 and 50+ age groups, DU admissions were negatively associated with temperature (both p < 0.05; model R 2 = 0.875 and 0.920, respectively), representing a winter peak and summer trough. Among the ≤19 age group, sunshine hours and rainfall are positively associated with DU admissions (both p < 0.001; R 2 = 0.565), representing a summer peak. CONCLUSION: Meteorological variables are associated with DU exacerbations, although the potential role of nonsteroidal anti-inflammatory drug (NSAID) use because of seasonal acute respiratory illness cannot be ruled out. We recommend in-depth studies using chart reviews of DU patients admitted during peak and trough (incidence) months to clarify whether meteorological factors or the associated seasonal peaks of respiratory and other illnesses involving NSAID use are responsible for the observed seasonality.
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