Evidence check: APOE in the context of fertility

The role of APOE (Apolipoprotein E) in fertility is not well established. APOE is primarily known for its association with Alzheimer's disease and cardiovascular risk, particularly the ε4 allele (rs429358, rs7412). Some observational studies have suggested possible links to female fertility, including effects on lipid metabolism, placental function, and oocyte quality. In male fertility, a few reports indicate associations with sperm parameters. However, the evidence is weak: most findings come from small studies, mechanistic hypotheses, or unconfirmed associations. The effects are polygenic and heavily influenced by lifestyle and environment. Direct-to-consumer genetic tests for APOE variants are not clinically validated for fertility prediction. Consumers should not base reproductive decisions on such markers alone and should seek comprehensive fertility evaluation. The evidence is rated as 'mixed/unclear' due to suggestive but inconclusive data.