This finding is strengthened by additional analyses of the ε2, ε3 and ε4 APOE Alzheimer’s disease risk alleles, with an overall reduction in the number of nocturnal sleep episodes observed with higher risk haplotypes (F(5, 72,578) = 5.36, P = 0.001) (Supplementary Table 2). Here, APOE is linked to Alzheimer disease.