The ICICLE-PD study aims to accurately characterise two independent cohorts of incident parkinsonsim in Newcastle-Gateshead and Cambridgeshire. A key objective is to identify patients who develop PD Dementia and the factors that predict its evolution. From this information, a simplified panel of tests that can be used to predict PDD will be established. ICICLE-PD will therefore provide a platform for studies investigating agents designed to help treat this complication of PD. Longitudinal follow up is on-going with assessments at 18 month intervals.