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Overall and cause-specific mortality in a cohort of farmers and their spouses
  1. Srishti Shrestha1,
  2. Christine G Parks1,
  3. Alexander P Keil2,
  4. David M Umbach3,
  5. Catherine C Lerro4,
  6. Charles F Lynch5,
  7. Honglei Chen6,
  8. Aaron Blair4,
  9. Stella Koutros4,
  10. Jonathan N Hofmann4,
  11. Laura E Beane Freeman4,
  12. Dale P Sandler1
  1. 1 Epidemiology Branch, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, USA
  2. 2 Department of Epidemiology, University of North Carolina School of Public Health, Chapel Hill, North Carolina, USA
  3. 3 Biostatistics and Computational Biology Branch, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, USA
  4. 4 Occupational and Environmental Epidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, Maryland, USA
  5. 5 Department of Epidemiology, University of Iowa College of Public Health, Iowa City, Iowa, USA
  6. 6 Department of Epidemiology and Biostatistics, College of Human Medicine, Michigan State University, East Lansing, Michigan, USA
  1. Correspondence to Dr Dale P Sandler, Epidemiology Branch, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA; sandler{at}niehs.nih.gov

Abstract

Objectives Lower mortality rates compared with the general population have been reported for Agricultural Health Study (AHS) participants (enrolled 1993–1997) followed through 2007. We extended analysis of mortality among AHS participants (51 502 private pesticide applicators, their 31 867 spouses and 4677 commercial pesticide applicators from North Carolina and Iowa) through 2015 and compared results using several analytical approaches.

Methods We calculated standardised mortality ratios (SMRs), causal mortality ratios (CMR) and relative SMRs (rSMR) using state-specific mortality rates of the general populations as the referent.

Results Over the average 16 years of follow-up (1999–2015), 9305 private applicators, 3384 spouses and 415 commercial applicators died. SMRs and CMRs, with expected deaths calculated using the person-time among the cohort and the general population, respectively, indicated lower overall mortality in all study subgroups (SMRs from 0.61 to 0.69 and CMRs from 0.74 to 0.89), although CMRs indicated elevated mortality in private applicators from North Carolina and in ever-smokers. In SMR analyses, there were fewer than expected deaths from many causes, but deaths from some external causes including transportation-related injuries and mechanical forces were elevated in private applicators. CMRs indicated higher than expected deaths from prostate cancer, lymphohaematopoietic cancers, Parkinson’s and Alzheimer’s disease, and chronic glomerulonephritis in private applicators, and non-Hodgkin’s lymphoma in spouses (from 1.19 to 1.53). rSMR results were generally elevated, similar to CMR findings.

Conclusions AHS participants experienced lower overall mortality than the general population.

Mortality from a few specific causes was increased in private applicators, specifically when CMR and rSMR approaches were used.

  • standardised mortality ratio
  • causal mortality ratio
  • relative standardised mortality ratio
  • farmers
  • Agricultural Health Study
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Footnotes

  • Contributors SS and DPS led the data analysis and prepared the first draft of the manuscript. APK and DMU provided statistical help. CGP, LEBF and DPS were involved in data acquisition and study management. All the authors were involved in data interpretation, reviewing and editing the manuscript, and providing final manuscript approval. All contributors meet the criteria for authorship.

  • Funding This work was supported by the Intramural Research Program of the National Institute of Health, National Institute of Environmental Health Sciences (Z01-ES-049030) and National Cancer Institute (Z01-CP-010119).

  • Competing interests None declared.

  • Patient consent for publication Not required.

  • Ethics approval The study was approved by the institutional review boards of the National Institute of Environmental Health Sciences (North Carolina, protocol number 11-E-N196), the National Cancer Institute (Maryland, protocol number OH93- NC-N013), Westat (Maryland), the University of Iowa (Iowa) and Battelle Health Sciences (North Carolina). We used AHS data release AHSREL201706.00 for the analysis.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data availability statement Requests for data, including the data used in this manuscript, are welcome as described on the study website (https://www.aghealth.nih.gov/collaboration/process.html). Data requests may be made directly at www.aghealthstars.com; registration is required. The Agricultural Health Study is an ongoing prospective study. The data sharing policy was developed to protect the privacy of study participants and is consistent with study informed consent documents as approved by the NIH Institutional Review Board. DPS is the NIEHS principal investigator of the Agricultural Health Study and is responsible for ensuring participant safety and privacy.

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