Research Report
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World J Gastroenterol. Apr 14, 2014; 20(14): 4037-4042
Published online Apr 14, 2014. doi: 10.3748/wjg.v20.i14.4037
Seasonal variations of acute appendicitis and nonspecific abdominal pain in Finland
Imre Ilves, Anne Fagerström, Karl-Heinz Herzig, Petri Juvonen, Pekka Miettinen, Hannu Paajanen
Imre Ilves, Anne Fagerström, Petri Juvonen, Pekka Miettinen, Hannu Paajanen, Department of Surgery, Kuopio University Hospital, FI-70211 Kuopio, Finland
Karl-Heinz Herzig, Institute of Biomedicine, Division of Physiology and Biocenter of Oulu, University of Oulu, FI-90014 Oulu, Finland
Karl-Heinz Herzig, Department of Psychiatry, Kuopio University Hospital, FI-70211 Kuopio, Finland
Author contributions: Herzig KH, Miettinen P and Ilves I designed the study; Fagerström A and Juvonen P gathered all data; Juvonen P, Ilves I and Miettinen P analyzed the data, investigated main changes and connections between the variables; Paajanen H and Miettinen P were main supervisors and were involved in editing the manuscript; Ilves I wrote the manuscript.
Correspondence to: Imre Ilves, MD, Department of Surgery, Kuopio University Hospital, PO Box 1777, FI-70211 Kuopio, Finland. imre.ilves@kuh.fi
Telephone: +35-81-7173311 Fax: +35-81-7172269
Received: August 17, 2013
Revised: October 10, 2013
Accepted: November 1, 2013
Published online: April 14, 2014
Processing time: 239 Days and 11.3 Hours
Abstract

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.

Keywords: Acute appendicitis; Appendectomy; Nonspecific abdominal pain; Incidence; Seasonal; Temperature; Humidity

Core tip: The incidence of acute appendicitis (AA) varies between countries and the etiology of the disease is still unclear. The aim of this study was to investigate whether seasonal changes had an effect on the incidence of AA or nonspecific abdominal pain (NSAP) in Finland between 1987 and 2007. We found that the incidence of AA, but not NSAP, was higher during the warm period of the year. In comparison to AA, NSAP was influenced by humidity and the incidence was lower during a period with lower levels of humidity.