title: Seasonality of primary care utilization for respiratory diseases in Ontario: a time-series analysis.
abstract: BACKGROUND
  Respiratory diseases represent a significant burden in primary care. Determining the temporal variation of the overall burden of respiratory diseases on the health care system and their potential causes are keys to understanding disease dynamics in populations and can contribute to the rational management of health care resources.
  
  
  METHODS
  A retrospective, cross-sectional time series analysis was used to assess the presence and strength of seasonal and temporal patterns in primary care visits for respiratory diseases in Ontario, Canada, for a 10-year period from January 1, 1992 to December 31, 2002. Data were extracted from the Ontario Health Insurance Plan database for people who had diagnosis codes for chronic obstructive pulmonary disease, asthma, pneumonia, or upper respiratory tract infections.
  
  
  RESULTS
  The results illustrate a clear seasonal pattern in visits to primary care physicians for all respiratory conditions, with a threefold increase in visits during the winter. Age and sex-specific rates show marked increases in visits of young children and in female adults. Multivariate time series methods quantified the interactions among primary care visits, and Granger causality criterion test showed that the respiratory syncytial virus (RSV) and influenza virus influenced asthma (p = 0.0060), COPD (p = 0.0038), pneumonia (p = 0.0001), and respiratory diseases (p = 0.0001).
  
  
  CONCLUSIONS
  Primary care visits for respiratory diseases have clear predictable seasonal patterns, driven primarily by viral circulations. Winter visits are threefold higher than summer troughs, indicating a short-term surge on primary health service demands. These findings can aid in effective allocation of resources and services based on seasonal and specific population demands.
authors.affiliation: Department of Family and Community Medicine, University of Toronto, 263 McCaul Street, Toronto, ON, M5T 2W7, Canada. rahim.moineddin@utoronto.ca
authors.forename: Rahim
authors.initials: R
authors.lastname: Moineddin
authors.forename: Jason X
authors.initials: JX
authors.lastname: Nie
authors.forename: Gabrielle
authors.initials: G
authors.lastname: Domb
authors.forename: Alan M
authors.initials: AM
authors.lastname: Leong
authors.forename: Ross E G
authors.initials: RE
authors.lastname: Upshur
mesh_terms: D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D015999:Multivariate Analysis; D009864:Ontario; D011320:Primary Health Care / Q000706:statistics & numerical data*; D012140:Respiratory Tract Diseases / Q000628:therapy*; D012189:Retrospective Studies; D012621:Seasons; D017678:Sex Distribution; D013995:Time