Natural history studies of Parkinson’s disease with adequate duration of follow up are scarce and fraught with difficulty due to selection bias and retrospective assessment in hospital series, confounding effects of comorbidity and problems of diagnostic accuracy.1 The pivotal study by Hoehn and Yahr2 on a cohort of 672 patients with “primary parkinsonism” came up with a rather bleak prognosis, with 61% of patients severely disabled or dead after 5 to 9 years of follow up, increasing to more than 80% of those who were followed up for more than 10 years. Overall mortality was increased to about threefold the expected rate in the general population. Such poor longterm outcome is thought to reflect the history of idiopathic Parkinson’s disease in the prelevodopa …