title: Effect of the shape of the exposure-response function on estimated hospital costs in a study on non-elective pneumonia hospitalizations related to particulate matter.
abstract: We used log-linear and log-log exposure-response (E-R) functions to model the association between PM2.5 exposure and non-elective hospitalizations for pneumonia, and estimated the attributable hospital costs by using the effect estimates obtained from both functions.
  
  
  
  We used hospital discharge data on 3519 non-elective pneumonia admissions from UZ Brussels between 2007 and 2012 and we combined a case-crossover design with distributed lag models. The annual averted pneumonia hospitalization costs for a reduction in PM2.5 exposure from the mean (21.4μg/m(3)) to the WHO guideline for annual mean PM2.5 (10μg/m(3)) were estimated and extrapolated for Belgium.
  
  
  
  Non-elective hospitalizations for pneumonia were significantly associated with PM2.5 exposure in both models. Using a log-linear E-R function, the estimated risk reduction for pneumonia hospitalization associated with a decrease in mean PM2.5 exposure to 10μg/m(3) was 4.9%. The corresponding estimate for the log-log model was 10.7%. These estimates translate to an annual pneumonia hospital cost saving in Belgium of €15.5 million and almost €34 million for the log-linear and log-log E-R function, respectively.
  
  
  
  Although further research is required to assess the shape of the association between PM2.5 exposure and pneumonia hospitalizations, we demonstrated that estimates for health effects and associated costs heavily depend on the assumed E-R function. These results are important for policy making, as supra-linear E-R associations imply that significant health benefits may still be obtained from additional pollution control measures in areas where PM levels have already been reduced.
authors.affiliation: Interuniversity Centre for Health Economics Research, Faculty of Medicine and Pharmacy, Vrije Universiteit Brussel, Laarbeeklaan 103, 1090 Brussel, Belgium. Electronic address: sdevos@vub.ac.be.
authors.forename: Stefanie
authors.initials: S
authors.lastname: Devos
authors.affiliation: Centre for Environmental Sciences, Hasselt University, Agoralaan building D, 3590 Diepenbeek, Belgium.
authors.forename: Bianca
authors.initials: B
authors.lastname: Cox
authors.affiliation: Mobility, Logistics and Automotive Technology Research Centre, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussel, Belgium.
authors.forename: Tom
authors.initials: T
authors.lastname: van Lier
authors.affiliation: Centre for Environmental Sciences, Hasselt University, Agoralaan building D, 3590 Diepenbeek, Belgium; Department of Public Health, University of Leuven (KULeuven), Herestraat 49, 3000 Leuven, Belgium.
authors.forename: Tim S
authors.initials: TS
authors.lastname: Nawrot
authors.affiliation: Interuniversity Centre for Health Economics Research, Faculty of Medicine and Pharmacy, Vrije Universiteit Brussel, Laarbeeklaan 103, 1090 Brussel, Belgium.
authors.forename: Koen
authors.initials: K
authors.lastname: Putman
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001530:Belgium; D002648:Child; D002675:Child, Preschool; D018592:Cross-Over Studies; D005260:Female; D006760:Hospitalization / Q000191:economics*; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D052638:Particulate Matter / Q000009:adverse effects*; D011014:Pneumonia / Q000139:chemically induced / Q000191:economics*; D055815:Young Adult
chemical_list: D052638:Particulate Matter
keywords: Distributed lag non-linear models; Exposure-response functions; Hospital costs; Particulate matter; Pneumonia