title: Presentations to Alberta emergency departments for asthma: a time series analysis.
abstract: OBJECTIVE
  Asthma is a common chronic respiratory condition, and exacerbations may cause individuals to seek care in emergency departments (EDs). This study examines the monthly patterns of asthma presentations to EDs in Alberta, Canada.
  
  
  METHODS
  All presentations to the ED for asthma from April 1999 to March 2011 were extracted from provincial administrative health databases. Data included age, sex, and health zone of residence. Crude rates per 100,000 population were calculated. Seasonal autoregressive integrated moving average (SARIMA) time-series models were developed.
  
  
  RESULTS
  There were a total of 362,430 ED presentations for asthma, and the monthly rate of presentation declined from 115.5 to 41.6 per 100,000 during the study period. Males made 50.1% of ED presentations, and adults made 52.8%. The absolute number of ED presentations for asthma declined in each of the five administrative health zones in the province, with smaller percentage decreases seen in the most urbanized zones (32.1%) than the other zones (46.9%). One SARIMA model closely predicted overall presentation rates as well as the rates of ED presentations for age and zone subgroups. These models showed strong seasonal components, with the strongest estimates occurring for the pediatric subgroup and the southernmost provincial zone.
  
  
  CONCLUSIONS
  Rates of ED presentations for asthma have been declining in this province during the past decade. The reasons for this decline warrant further exploration. The SARIMA models quantified the temporal patterns and may be helpful for planning research and health care service needs.
authors.affiliation: Department of Pediatrics, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Rhonda J
authors.initials: RJ
authors.lastname: Rosychuk
authors.affiliation: Patient Health Outcomes Research and Clinical Effectiveness Unit, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Erik
authors.initials: E
authors.lastname: Youngson
authors.affiliation: Department of Emergency Medicine, University of Alberta, Edmonton, Alberta, Canada.|School of Public Health, University of Alberta, Edmonton, Alberta, Canada.|Alberta Health Services, Edmonton, Alberta, Canada.
authors.forename: Brian H
authors.initials: BH
authors.lastname: Rowe
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000416:Alberta; D001249:Asthma / Q000628:therapy*; D002648:Child; D016208:Databases, Factual; D004636:Emergency Service, Hospital / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012111:Residence Characteristics; D012737:Sex Factors