The impact of the environmentally sustainable EAT-Lancet diet on dementia risk remains poorly understood. The aim was to investigate associations between the EAT-Lancet diet and incident dementia.

Associations of the EAT-Lancet diet with all-cause dementia, Alzheimer's disease (AD), and vascular dementia (VaD) were investigated among 25,898 participants from the Malmö Diet and Cancer study, Sweden. Participants aged 45–73 years were recruited for the baseline examination between 1991 and 1996, and the mean follow-up time was 18 years. To assess robustness of estimations, we used seven previously constructed EAT-Lancet diet scores. Multi-adjusted Cox proportional hazard analyses were performed, with results presented per 10 % in increment scores. Additionally, we explored the potentially modifying effect of APOE ε4 status in this context.

With one of the scores, higher adherence to the EAT-Lancet diet was associated with a reduced risk of AD and all-cause dementia. Moreover, the results suggest an interplay between the EAT-Lancet diet and APOE ε4 status. A risk-reducing effect was observed among APOE ε4 non-carriers with three of the scores in relation to AD, and with five of the scores in relation to all-cause dementia. No associations were observed among APOE ε4 carriers, or in relation to VaD.

The results indicate a risk reducing effect of adhering to the EAT-Lancet diet among APOE ε4 non-carriers, and no negative effects on dementia risk were detected. Future studies should consider the potentially modifying effect of APOE ε4 status, and the implications of methodological differences in measuring adherence to the EAT-Lancet diet.