Overall and cause-specific mortality in a cohort of farmers and their spouses

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\u2009502 private pesticide applicators, their 31\u2009867 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.