In case anyone is interested, I researched about links with APOE / FOXO in AD and ageing, and found that the term is called 'genetic buffering' Here is the paper I found (published this year) about buffering and affects between the different genes.
However it seems to mention a different FOX03 snp. Thought it was quite interesting though.
"APOE haplotype and rs9486902 in FOXO3 showed an interaction effect. Per genotype, there may be an interaction between the APOE4 allele and the FOXO3 CC genotype; FOXO3 CC could be a buffering genotype for the deleterious APOE4. Pathway analysis in IPA® showed that one mechanism of interaction could be through amyloid beta precursor protein, APP. FOXO3 is part of the insulin/insulin-like growth factor 1 signal pathway and has been associated with longevity , and FoxO proteins have been implicated in AD ."
Lipid and Alzheimer’s disease genes associated with healthy aging and longevity in healthy oldest-old https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5400530/
Although it also seems possibly FOXO3 itself can be involved in AD and not sure if in a good way
Linking Alzheimer's disease to insulin resistance: the FoxO response to oxidative stress. https://www.ncbi.nlm.nih.gov/pubmed/20966918/
Overall I have stopped thinking about how they interact as was getting bogged down, decided that it seems that the same things help both APOE4 and FOX which are intermittent fasting, low GI carbs, exercise etc. and it's best to focus on this in general rather than the details. It is all so complex.