title: Healthy worker survivor analysis in an occupational cohort study of Dutch agricultural workers.
abstract: OBJECTIVE
  High microbial exposures in farmers and agricultural workers are associated with less atopy. Although it has been speculated that healthy worker survival could be an explanation, this has not been studied so far. Therefore, we investigated the presence of healthy worker survival in a five-year follow-up study of an occupational cohort of Dutch farmers and agricultural industry (company) workers.
  
  
  METHODS
  We compared baseline demographic characteristics, respiratory health, atopy and endotoxin exposure of 259 workers followed up with 124 workers lost to follow-up. Additionally, baseline health status of 31 participants who had changed to lower exposure jobs at follow-up was compared to those with similar or higher exposure jobs at follow-up.
  
  
  RESULTS
  In general, no major healthy worker survival effect was found. Nonetheless, small differences were observed between subjects included in follow-up and those lost to follow-up. Those lost to follow-up were older, had a lower peak expiratory flow, and were less often raised on a farm. Company workers lost to follow-up with a farm childhood had more often self-reported allergy, but this was not observed for subjects with atopic sensitization or other respiratory symptoms. No differences were found for any of the studied characteristics in participants with lower exposure at follow-up compared to participants with similar or higher exposure at follow-up.
  
  
  CONCLUSIONS
  No major healthy worker survival is present in this organic dust exposed cohort. Differences between participants lost to follow-up and participants included in follow-up with regard to health characteristics are small and unlikely to explain the previously reported inverse associations between endotoxin exposure and atopy.
authors: Division of Environmental Epidemiology, Institute for Risk Assessment Sciences, Utrecht University, Utrecht, The Netherlands. e.a.j.spierenburg@uu.nl.
authors: E A J
authors: EA
authors: Spierenburg
authors: Division of Environmental Epidemiology, Institute for Risk Assessment Sciences, Utrecht University, Utrecht, The Netherlands.
authors: L A M
authors: LA
authors: Smit
authors: Division of Environmental Epidemiology, Institute for Risk Assessment Sciences, Utrecht University, Utrecht, The Netherlands.
authors: D
authors: D
authors: Heederik
authors: Department of Pathology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands.|Groningen Research Institute for Asthma and COPD (GRIAC), University Medical Center Groningen, University of Groningen, Groningen, The Netherlands.
authors: P
authors: P
authors: Robbe
authors: Department of Pathology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands.|Groningen Research Institute for Asthma and COPD (GRIAC), University Medical Center Groningen, University of Groningen, Groningen, The Netherlands.
authors: M N
authors: MN
authors: Hylkema
authors: Division of Environmental Epidemiology, Institute for Risk Assessment Sciences, Utrecht University, Utrecht, The Netherlands.
authors: I M
authors: IM
authors: Wouters
mesh_terms: D000328:Adult; D000382:Agricultural Workers' Diseases / Q000382:microbiology / Q000401:mortality*; D000383:Agriculture; D015331:Cohort Studies; D004731:Endotoxins / Q000032:analysis* / Q000633:toxicity; D005260:Female; D005500:Follow-Up Studies; D015989:Healthy Worker Effect; D006801:Humans; D006969:Hypersensitivity, Immediate / Q000382:microbiology / Q000401:mortality*; D059012:Lost to Follow-Up; D008297:Male; D008875:Middle Aged; D009426:Netherlands / Q000453:epidemiology; D016273:Occupational Exposure / Q000009:adverse effects / Q000032:analysis*; D016019:Survival Analysis; D013997:Time Factors
chemical_list: D004731:Endotoxins
keywords: Agricultural workers; Endotoxin; Farmers; Healthy worker effect; Occupational exposure