Trends in Prevalence of Dementia in French Farmers from Two Epidemiological Cohorts

Objectives To determine the prevalence of dementia and cognitive impairment in older people across generations. Design Two prospective cohort studies (Personnes Agees QUID (PAQUID), Aging Multidisciplinary Investigation (AMI)). Setting Baseline data from two subsamples of older farmers in southwestern France. Participants PAQUID (n = 595) and AMI (n = 906) participants aged 65 and older living at home at baseline (1988 PAQUID, 2008 AMI). Measurements Two methods were used to diagnose dementia: a clinical consensus diagnosis and a computer-assisted taxonomy approach (cognitive impairment with disability (CIWD)) using Mini-Mental State Examination and instrumental activity of daily living scores. Crude and standardized prevalences (using PAQUID age-sex structure) and 95% confidence intervals were calculated, and logistic regression was used to explore confounding. Results The prevalence of consensus diagnosis of dementia was higher in AMI in 2008 than in PAQUID in 1988 (12.0% vs 5.7%, P < .001), whereas the reverse was observed for CIWD (14.8% vs 23.8%, P < .001), confirmed by logistic regressions (odds ratio (OR)AMIvsPAQUID = 2.50, 95% confidence interval (CI) = 1.52–4.12; ORAMIvs.PAQUID = 0.60, 95% CI = 0.42–0.87, respectively). Educational level increased and management of vascular risk factors improved over the study period, and health and living conditions improved globally. Conclusion These findings suggest global cognitive and functional improvement in old farmers (the prevalence of CIWD decreased by 40% over 20 years) and simultaneously a marked change in the subjective boundary between dementia and nondementia according to clinicians.