In addition, we analysed potential associations between KLK6 levels; age; APOE genotype; total apoE level (assessed in the cross-sectional setting only); and the AD biomarkers amyloid-β 1–42 (Aβ42), amyloid-β 1–40 (Aβ40), total tau (t-tau) and phosphorylated tau (p-tau). The gene discussed is APOE; the disease is Alzheimer disease.