Interaction between APOE ε4 and dietary protein intake on cognitive decline: a longitudinal cohort study

Summary Objective To exam the association of cognitive decline with APOE e4 allele carriage and dietary protein intake and investigate whether there is a gene-diet (GxD) interaction of APOE e4 allele carriage and dietary protein intake on cognitive decline in a nationwide cohort of older adults. Methods A cohort study of participants from Chinese Longitudinal Healthy Longevity Survey was conducted from 2008 t0 2014. A total of 3,029 participants (mean age of 77.0 years, SD=9.0; 49.3% were women) was enrolled. We genotyped APOE e4 allele for each participant and calculated the diversity of dietary protein intake (DDPI) by summing up the frequency of intake of the 6 protein-rich foods (meats, fish, eggs, nuts, dairy products, and bean products). We assessed cognitive function using the Mini-Mental State Examination (MMSE). We used ordinal regression model to estimate the independent and joint effects of APOE e4 carrier and dietary protein intake on cognitive decline, adjusting for potential confounders of age, sex, education, socio-economic status, lifestyles, BMI, and cardiometabolic conditions. Results There was significant association between carrying APOE e4 allele and faster cognitive decline (Odds ratio: 1.19, 95% CI= 1.00-1.42), independent of potential confounders. While the associations of DDPI and the intake of 6 protein-rich foods with cognitive decline did not reach any statistical significance. We observed significant interactions of APOE e4 with DDPI and fish intake, at multiple correction-adjusted Ps Conclusions The results of this study support the hypothesis that diversified protein food intake in addition to frequent fish intake may reduce the detrimental effect of APOE e4 on cognitive health.