APOE and dementia: In modelling combining all biomarkers with baseline age, gender and MDS-UPDRS 3, only APOE ε4 status (HR 2.75, 95% CI 1.44 to 5.24, p=0.002) and Nfl (HR 2.09, 95% CI 1.16 to 3.76, p=0.014) continued to significantly predict progression to dementia.