title: Population demographic indicators associated with incidence of pyloric stenosis.
abstract: OBJECTIVE
  To calculate incidence rates of pyloric stenosis (estimated by the rate of pyloromyotomy) among infants in Ontario and determine their association with population sociodemographic indicators.
  
  
  METHODS
  Pyloromyotomy rates were calculated from hospital discharge data from 1993 through 2000. Four-year data (1993-1996 and 1997-2000) were combined to ensure the stability of the rates. Small-area variations in pyloromyotomy rates and correlations between sociodemographic indicators were studied.
  
  
  RESULTS
  Approximately 84.0% of the patients were male infants (younger than 1 year). The sex-adjusted pyloromyotomy rates were 1.57 and 1.86 per 1000 with a 3.4-fold and 3.0-fold regional variation in 1993-1996 and 1997-2000, respectively. Urban areas consistently had the lowest pyloromyotomy rate (1.04 and 1.11 per 1000 in Metropolitan Toronto), but the highest rates were from more rural areas (3.30 and 3.38 per 1000 in Quinte, Kingston, Rideau). After adjusting for socioeconomic status and availability of surgeons in the region, living in a rural area remained a significant factor associated with a higher incidence of pyloromyotomy. The risk of pyloromyotomy for an infant who lives in a region with more than two thirds of its area classified as rural was 1.79 (95% confidence interval, 1.23-2.61; P<.005).
  
  
  CONCLUSIONS
  The observed changes in incidence and a higher rate among male infants are consistent with results from previous comparative studies conducted in North America and Sweden. The rural/urban differences suggest that environmental influences related to living in these areas may have a role in the etiology of pyloric stenosis. Further research is needed to evaluate these differences.
authors.affiliation: Population Health Sciences, Research Institute and Departments of Surgery and Pediatrics, Hospital for Sick Children, Toronto, Ontario.
authors.forename: Teresa
authors.initials: T
authors.lastname: To
authors.forename: Anne
authors.initials: A
authors.lastname: Wajja
authors.forename: Paul W
authors.initials: PW
authors.lastname: Wales
authors.forename: Jacob C
authors.initials: JC
authors.lastname: Langer
mesh_terms: D003710:Demography; D013505:Digestive System Surgical Procedures / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D015994:Incidence; D007223:Infant; D008297:Male; D009864:Ontario / Q000453:epidemiology; D011707:Pyloric Stenosis / Q000453:epidemiology* / Q000601:surgery; D012424:Rural Population / Q000706:statistics & numerical data; D017678:Sex Distribution; D014505:Urban Population / Q000706:statistics & numerical data