Supplementary Material for: Impact of the apolipoprotein E ε4 allele on cognition and omega-3 fatty acid levels in the plasma membrane of red blood cells in healthy elderly Japanese population

The ε4 allele of the apolipoprotein E (APOE4) gene is a well-known risk factor for the onset and development of late-onset Alzheimer’s disease (AD). Lipid metabolism also plays a key role in AD. However, data on the association between APOE4, cognitive function, and blood lipid metabolism, particularly fatty acid metabolism, in the healthy elderly Japanese population are lacking. To address this issue, we analyzed the baseline data of 506 healthy elderly Japanese individuals (mean age: 73 ± 0.4 years) from Shimane Prefecture, Japan, who participated in six intervention trials conducted between 2008 and 2020. Among them, participants with mild cognitive impairment (MCI) were divided into the following two groups: APOE4 carriers (n = 104) and non-carriers (n = 321). Compared with the non-carriers, the APOE4 carriers had significantly lower scores in the “Recalling five objects” subitem of Hasegawa’s Dementia Scale—Revised and longer total times in the Cognitive Assessment for Dementia iPad version. The ratio of docosahexaenoic acid (DHA) to arachidonic acid was significantly decreased, and the erythrocyte eicosapentaenoic acid (EPA) and DHA levels tended to be reduced in APOE4 carriers. These findings suggest a possible association between the APOE4 allele and reduced erythrocyte EPA and DHA levels, even in healthy elderly Japanese individuals with high ω-3 fatty acid intake. Such alterations in lipid metabolism may be linked to cognitive vulnerability in older adults and individuals with MCI.