Approvals, recruitment, eligibility and consent

Relevant approvals were obtained including ethics (North West – Preston Research Ethics Committee), research governance and local university approvals. The study was conducted in accordance with the principles of Good Clinical Practice. Recruitment of IPD patients was from Lancashire Teaching Hospitals (LTH) and Salford Royal Foundation Trust. Eligibility criteria for IPD participants were a clinical diagnosis of IPD fulfilling UK Parkinson’s disease society brain bank criteria (http://www.ncbi.nlm.nih.gov/projects) without known clinical CVD (no history of TIA or stroke) or dementia.²¹ Participants with CVD were recruited from patients at LTH with a clinical diagnosis of stroke or TIA within the previous two years (at least three months post-onset) supported by relevant brain imaging (control positive, CP). Controls without a history of either IPD or clinical CVD were also recruited (control negative, CN). All groups were matched for age. All participants were required to provide written informed consent and had capacity to do so.