We will then discuss potential vulnerability and protective characteristics that may moderate the association between OSA and cognitive decline, namely, age, sex, menopause, obesity, diabetes mellitus, hypertension, cardiovascular diseases, smoking, excessive alcohol consumption, depression, air pollution, Apolipoprotein E ε4 (ApoE4) allele, physical activity, and cognitive reserve. The gene discussed is APOE; the disease is obesity due to melanocortin 4 receptor deficiency.