Seasonal variations of acute appendicitis and nonspecific abdominal pain in Finland

AIM: To investigate whether seasonal changes had an effect on the incidence of acute appendicitis (AA) or nonspecific abdominal pain (NSAP). METHODS: We carried out a national register study of all patients with a hospital discharge diagnosis of AA and acute NSAP in Finland. Data were analyzed for the whole country and correlated to seasonal and weather parameters (temperature, humidity). Moreover, additional sub-analyses were performed for five geographically different area of Finland. RESULTS: The observation period spanned 21 years, with 186558 appendectomies, of which 137528 (74%) cases were reported as AA. The incidence of AA declined for 32% over the study period. The average incidence of the NSAP was 34/10000 per year. The mean annual temperature, but not relative humidity, showed clear geographical variations. The incidence of AA decreased significantly during the cold months of the year. No correlation was detected between temperature and incidence of NSAP. Humidity had a statistically significant impact on NSAP. CONCLUSION: The incidence of acute appendicitis is declining in Finland. We detected a clear seasonality in the incidence of AA and NSAP.