The association between farming, cognitive function, and regional brain volumes in older adults: results from the NEIGE cohort

The association between farming and cognitive decline remains controversial. This study examined the association of weekly farming hours with cognitive function and dementia-related brain volumes. This cross-sectional study included 447 community-dwelling adults aged 65–84 years from the Neuron to Environmental Impact Across Generations Study in Japan. Participants were categorized by weekly farming hours: non-farming, < 9, 9–21, or 21 + hours/week. Low cognitive function was defined as a score of ≤ 23 on the Japanese version of the Mini-Mental State Examination (MMSE-J). Multivariable logistic regression was used for low cognitive function, as the primary outcome. Linear regression was used for continuous MMSE-J scores and dementia-related brain volumes. As an additional analysis, inverse-probability weighting was applied. Low cognitive function was present in 37 participants (8.3%). Farming for 21 + hours/week was associated with lower odds of low cognitive function than the non-farming group, adjusted for covariates (adjusted OR = 0.21; 95% CI: 0.05–0.93). Inverse-probability weighting showed that the estimated potential probability of low cognitive function was 6.5% and 1.9% for non-farming and 21 + hours/week farming, respectively, yielding an average treatment effect of − 4.6 percentage points (95% CI: −8.8 to − 0.4). However, farming hours were not significantly associated with continuous MMSE-J scores or dementia-related brain volumes. Farming for 21 + hours/week was associated with lower odds of low cognitive function. However, this exploratory finding warrants cautious interpretation given the small number of events and inconsistent results across cognitive and neuroimaging outcomes. Longitudinal studies are needed to clarify temporality and causality.