title: Estimating influenza-related hospital admissions in older people from GP consultation data.
abstract: This study seeks to determine the association between general practice (GP) consultations for influenza-like illness (ILI) and hospital admissions, and to estimate the number of excess hospitalisation due to ILI epidemics, for two age-groups: 51-65 years and >65 years.
  
  
  METHODS
  Structural time series models (STSM) with stochastic trend and seasonal components were developed. Weekly data from Switzerland for 1987 to 1996/1997 were used. Hospital admission rates for pneumonia and influenza (P&I) and other respiratory conditions (ORC) were regressed against GP consultation rates. Excess hospitalisations were calculated as the difference between predicted hospital admissions during influenza epidemics and predicted hospital admissions using a baseline GP consultation rate.
  
  
  RESULTS
  Excess admission rates were substantially higher in the oldest age-group (51-65 years: P&I 4.42, ORC 2.14; >65 years: P&I 6.30, ORC 4.74 per 10,000 population per year). The models explained between 43 and 76% of the variation in hospital admissions. The seasonal patterns were stable over the 10 years modelled and the variances of the trends were small.
authors.affiliation: York Health Economics Consortium Ltd., Market Square, University of York, England YO10 5NH, UK. pas8@york.ac.uk
authors.forename: Paul A
authors.initials: PA
authors.lastname: Scuffham
mesh_terms: D000367:Age Factors; D000368:Aged / Q000706:statistics & numerical data*; D000465:Algorithms; D003627:Data Interpretation, Statistical; D016208:Databases, Factual; D005194:Family Practice / Q000706:statistics & numerical data*; D005260:Female; D006760:Hospitalization / Q000706:statistics & numerical data*; D006801:Humans; D007251:Influenza, Human / Q000453:epidemiology*; D008297:Male; D008875:Middle Aged; D011014:Pneumonia / Q000453:epidemiology; D012017:Referral and Consultation; D012621:Seasons; D013269:Stochastic Processes; D013557:Switzerland / Q000453:epidemiology