Baril et al. showed that more severe insomnia symptoms were associated with lower performance on global cognition, which was especially apparent in the apolipoprotein E (APOE) ε4 allele carriers, suggesting that poor sleep might be particularly detrimental when the brain is already vulnerable to neurodegeneration.34The presence of apolipoprotein E2 to E4 also showed no difference between patients who persisted with insomnia. This evidence concerns the gene APOE and insomnia measurement.