Although it would have been interesting to examine the effect of participants being heterozygous or homozygous for the APOE ε4 allele, due to the very small sample size of APOE ε4 homozygous participants (for PYY n = 26 of APOE ε4 heterozygous and n = 7 of APOE ε4 homozygous; for Leptin n = 36 of APOE ε4 heterozygous and n = 11 of APOE ε4 homozygous) in the AD group, undertaking such an analysis was not feasible. Here, PYY is linked to Alzheimer disease.