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

Background
Genetic and lifestyle factors influence the risk of developing dementia. Diet is one of the modifiable lifestyle factors thought to affect risk, but it is unclear whether there is an interplay with genetic risk factors in relation to incident dementia.

Method
Data was derived from the population-based Gothenburg H70 Birth Cohort Studies based in Sweden, including 602 dementia-free 70-year-olds (born 1922 or 1930; 64% women) with dietary and genetic data followed for incident dementia until 2016. Two dietary patterns were derived with reduced rank regression analysis, one healthy (e.g., fruits, vegetables, fish) and one western (e.g., full-fat dairy products, refined bread, red and processed meat). Genetic risk was determined by APOE ε4 status and four non-APOE AD-polygenic risk scores (AD-PRSs). Gene-diet interactions in relation to incident dementia were analysed with cox regression models. If an interaction at a p-value threshold of p< 0.20 was detected, stratified analyses were performed. Analyses were adjusted for sex, energy intake, birth year, age at examination, educational level, physical activity level, cardiovascular risk factors and 10 principal components (to correct for population stratification).

Result
There was an interaction between APOE ε4 status and a healthy and a western dietary pattern in relation to incident dementia (p=0.13 and p=0.07), while no interactions were found between AD-PRSs and dietary patterns. Those with higher adherence to a healthy dietary pattern had a reduced risk of dementia (HR 0.77; 95% CI 0.64–0.94, p=0.008) among ε4 non-carriers, but not among ε4 carriers. There was a borderline association between a western dietary pattern and an increased risk of dementia among ε4 carriers (HR 1.25; 95% CI 0.97–1.61, p=0.08), while no association was observed among ε4 non-carriers.

Conclusion
The results suggest an interplay between APOE ε4 status and adherence to dietary patterns in relation to incident dementia. The findings from this study could be of importance for dementia prevention strategies and for future intervention studies investigating the effect of dietary patterns in relation to dementia incidence.