title: Seasonal variation of hypertrophic pyloric stenosis: a population-based study.
abstract: BACKGROUND
  Seasonal variation in the incidence of hypertrophic pyloric stenosis (HPS) has been long debated. The goal of this study was to determine if seasonal variation exists in the incidence of pyloric stenosis.
  
  
  METHODS
  A population-based cohort consisted of all infants in the province of Ontario, Canada with HPS from 1993 to 2000. The incidence of HPS per season was adjusted by birth rate and expressed as number of pyloromyotomies per 100,000 infants less than 12 months of age. One-way analysis of variance was used to compare HPS incidence between seasons. Further time series and spectral analysis were performed to examine for seasonal variation.
  
  
  RESULTS
  There were 1,777 infants included in the population-based cohort. June was the month with the highest rate of HPS. The highest rate of pyloromyotomy occurred in the summer 14.92 and the lowest in the winter 10.73, this difference was statistically significant (p = 0.01). Spectral analysis showed that June was the month with the highest rate and February had the lowest rates p = 0.0014.
  
  
  CONCLUSIONS
  Hypertrophic pyloric stenosis more commonly presents in the summer. Seasonal variation suggests a possible etiological role for environmental factors.
authors.affiliation: Division of Pediatric Surgery, King Fahad Hospital, King Abdulaziz Medical City, National Guard Health Affairs, Riyadh, Saudi Arabia. zamakhshary@gmail.com
authors.forename: Mohammed F
authors.initials: MF
authors.lastname: Zamakhshary
authors.forename: Sanjeev
authors.initials: S
authors.lastname: Dutta
authors.forename: Teresa
authors.initials: T
authors.lastname: To
authors.forename: Derek
authors.initials: D
authors.lastname: Stephens
authors.forename: Jacob C
authors.initials: JC
authors.lastname: Langer
authors.forename: Paul W
authors.initials: PW
authors.lastname: Wales
mesh_terms: D013505:Digestive System Surgical Procedures / Q000379:methods; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D007223:Infant; D008297:Male; D009864:Ontario / Q000453:epidemiology; D011159:Population Surveillance / Q000379:methods*; D011379:Prognosis; D046248:Pyloric Stenosis, Hypertrophic / Q000453:epidemiology* / Q000601:surgery; D011708:Pylorus / Q000601:surgery; D012189:Retrospective Studies; D012307:Risk Factors; D012621:Seasons