Dementia and Cognitive Decline in Older Adulthood: Are Agricultural Workers at Greater Risk?

Objectives To examine whether long-term exposure to agricultural work is associated with dementia prevalence and the rate of cognitive change in older adulthood. Methods We employed data from the Health and Retirement Study (1998-2014). Multiple logistic regression was used to determine whether a longest-held job in the agricultural sector was associated with differences in dementia prevalence. We examined if hearing impairment, depression and physical health indicators mediated the relationship between agricultural work and cognitive functioning. Sub-group analyses were done by age, retirement status, job tenure, and cognitive domain. We employed growth curve models to investigate implications of agricultural work on age trajectories of cognitive functioning. Results Longest-held job in agriculture, fishing, and forestry (AFF) was associated with 46% greater odds of having dementia. The relationship between AFF exposure and cognitive functioning was not mediated by hearing impairment, depression, or physical health indicators. Results were stronger among younger and retired older adults as well as those with extensive job tenure. AFF exposure was associated with lower scores in working memory and attention and processing speed. Growth curve models indicated that while agricultural work exposure was associated with lower initial levels of cognitive functioning, over time the pattern reversed with individuals in non-AFF jobs showing more accelerated cognitive decline. Discussion Consistent with European studies, results from the U.S. also demonstrate a higher prevalence of dementia among agricultural workers. The cognitive reserve framework may explain the seemingly paradoxical result on age patterning of cognitive performance across older adults with different work histories.