Interactions between dietary patterns and genetic factors in relation to incident dementia among 70-year-olds

PURPOSE: To investigate potential interactions between dietary patterns and genetic factors modulating risk for Alzheimer’s disease (AD) in relation to incident dementia. METHODS: Data were derived from the population-based Gothenburg H70 Birth Cohort Studies in Sweden, including 602 dementia-free 70-year-olds (examined 1992–93, or 2000–02; 64% women) followed for incident dementia until 2016. Two factors from a reduced rank regression analysis were translated into dietary patterns, one healthy (e.g., vegetables, fruit, and fish) and one western (e.g., red meat, refined cereals, and full-fat dairy products). Genetic risk was determined by APOE ε4 status and non-APOE AD-polygenic risk scores (AD-PRSs). Gene–diet interactions in relation to incident dementia were analysed with Cox regression models. The interaction p value threshold was < 0.1. RESULTS: There were interactions between the dietary patterns and APOE ε4 status in relation to incident dementia (interaction p value threshold of < 0.1), while no evidence of interactions were found between the dietary patterns and the AD-PRSs. Those with higher adherence to a healthy dietary pattern had a reduced risk of dementia among ε4 non-carriers (HR: 0.77; 95% CI: 0.61; 0.98), but not among ε4 carriers (HR: 0.86; CI: 0.63; 1.18). Those with a higher adherence to the western dietary pattern had an increased risk of dementia among ε4 carriers (HR: 1.37; 95% CI: 1.05; 1.78), while no association was observed among ε4 non-carriers (HR: 0.99; CI: 0.81; 1.21). CONCLUSIONS: The results of this study suggest that there is an interplay between dietary patterns and APOE ε4 status in relation to incident dementia. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s00394-021-02688-9.