title: Comorbidity and coexisting symptoms and infections presented in general practice by COPD patients: Does livestock density in the residential environment play a role?
abstract: Patients with chronic obstructive pulmonary disease (COPD) constitute a potentially susceptible group towards environmental exposures such as livestock farm emissions, given their compromised respiratory health status. The primary aim of this study was to examine the association between livestock exposure and comorbidities and coexisting symptoms and infections in COPD patients.
  
  
  
  Data were collected from 1828 COPD patients (without co-occurring asthma) registered in 23 general practices and living in a rural area with a high livestock density. Prevalence of comorbid diseases/disorders and coexisting symptoms/infections were based on electronic health records from the year 2012. Various indicators of individual exposure to livestock were estimated based on residential addresses, using a geographic information system.
  
  
  
  At least one comorbid disorder was present in 69% of the COPD patients (especially cardiac disorders and depression, while 49% had at least one coexisting symptom and/or infection (especially upper respiratory tract infections, respiratory symptoms and pneumonia). Half of the COPD-patients resided less than 500m of the nearest farm. Some positive as well as inverse associations were found between the examined outcomes and exposure estimates, although not consistent.
  
  
  
  Despite the high prevalence of coexisting chronic and acute conditions presented in primary care by in COPD patients, this investigation found no convincing evidence for an association with livestock exposure estimates. There is a need for a replication of the present findings in studies with a longitudinal design, on different groups of potentially susceptible patients. Future research should also elucidate the biological plausibility of possible protective effects of exposure.
authors.affiliation: Netherlands Institute for Health Services Research (NIVEL), Utrecht, The Netherlands. Electronic address: c.baliatsas@nivel.nl.
authors.forename: Christos
authors.initials: C
authors.lastname: Baliatsas
authors.affiliation: Netherlands Institute for Health Services Research (NIVEL), Utrecht, The Netherlands; Institute for Risk Assessment Sciences (IRAS), Utrecht University, Utrecht, The Netherlands.
authors.forename: Floor
authors.initials: F
authors.lastname: Borlée
authors.affiliation: Netherlands Institute for Health Services Research (NIVEL), Utrecht, The Netherlands.
authors.forename: Christel E
authors.initials: CE
authors.lastname: van Dijk
authors.affiliation: Netherlands Institute for Health Services Research (NIVEL), Utrecht, The Netherlands.
authors.forename: Baukje
authors.initials: B
authors.lastname: van der Star
authors.affiliation: Netherlands Institute for Health Services Research (NIVEL), Utrecht, The Netherlands.
authors.forename: Jan-Paul
authors.initials: JP
authors.lastname: Zock
authors.affiliation: Institute for Risk Assessment Sciences (IRAS), Utrecht University, Utrecht, The Netherlands.
authors.forename: Lidwien A M
authors.initials: LAM
authors.lastname: Smit
authors.affiliation: Netherlands Institute for Health Services Research (NIVEL), Utrecht, The Netherlands.
authors.forename: Peter
authors.initials: P
authors.lastname: Spreeuwenberg
authors.affiliation: Institute for Risk Assessment Sciences (IRAS), Utrecht University, Utrecht, The Netherlands.
authors.forename: Dick
authors.initials: D
authors.lastname: Heederik
authors.affiliation: Netherlands Institute for Health Services Research (NIVEL), Utrecht, The Netherlands.
authors.forename: C Joris
authors.initials: CJ
authors.lastname: Yzermans
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D015897:Comorbidity; D004781:Environmental Exposure; D000072480:Farms; D005260:Female; D006801:Humans; D007239:Infections / Q000453:epidemiology*; D058751:Livestock; D008297:Male; D008875:Middle Aged; D029424:Pulmonary Disease, Chronic Obstructive / Q000453:epidemiology*; D012111:Residence Characteristics
keywords: COPD; Comorbidity; Environmental exposure; Epidemiology; General practice; Livestock