Letter in response to Picillo et al., in relation to Szewczyk-Krolikowski et al.: the influence of age and gender on motor and non-motor features of early Parkinson's disease: initial findings from the Oxford Parkinson disease Center (OPDC) discovery cohort
1 School of Social and Community Medicine, University of Bristol, United Kingdom.
2 Nuffield Department of Clinical Neurosciences, Division of Clinical Neurology, University of Oxford, United Kingdom.
3 Nuffield Department of Clinical Neurosciences, Division of Clinical Neurology, University of Oxford, United Kingdom; Oxford Parkinson Disease Centre, University of Oxford, United Kingdom; Department of Clinical Neurology, John Radcliffe Hospital, Oxford, United Kingdom. Electronic address: michele.hu@ndcn.ox.ac.uk.