The effect of occupation type on risk of Alzheimer’s disease in men and women

Abstract

ObjectivesTo examine the association between the principal lifetime occupation and the incidence of Alzheimer’s disease (AD) in men and women in a southern European population aged 55 years or more. Study designA community-dwelling sample of 3883 dementia-free individuals aged 55 years or over was classified according the Spanish National Classification of Occupations (CNO-11) and the International Standard Classification of Occupations (ISCO-08) in a four-wave epidemiological study. Medical and psychiatric histories were collected using standardized instruments, including the Mini-Mental Status Examination (MMSE), the History and Aetiology Schedule (HAS), the Geriatric Mental State-AGECAT, and a risk factor Questionnaire. Cases of AD were diagnosed according to DSM-IV criteria. Cox regression models were performed, stratified by sex. Main outcome measuresCases of AD according to the main occupation and sex. ResultsIn men, compared with the “white collar” category, the risk of AD in “farmers” was 66% times lower, after controlling for potential confounding factors (HR: 0.34; 95% CI: 0.08–1.33). It did not reach statistical significance but the magnitude was large (Cohen’s d = 0.84). In women, “farmers” had almost 50% less risk of AD after controlling for all potential confounding factors (HR: 0.55; 95% CI: 0.17–1.78), compared with homemakers, but with a medium effect size (Cohen’s d = 0.46). ConclusionsMen and women farmers had a lower risk of AD, reinforcing the importance of lifetime occupation in the risk of AD at older ages. These results could suggest some environmental hypotheses.