Background: Parkinson's disease is a common disorder among older people. Accurate epidemiological information is essential to identify possible aetiological factors, plan health services and set priorities for medical research.

Objective: to determine the incidence of idiopathic Parkinson's disease in a defined geographical area in the North-East of England.

Methods: using a prospective, longitudinal design, we sought to identify every new case of Parkinson's disease arising in the Newcastle and Gateshead area in the North-East of England. The base population comprised 488 576 individuals and multiple sources of case ascertainment were employed. All the patients with newly diagnosed idiopathic Parkinson's disease or parkinsonism between 1 June 2009 and 31 May 2011 were invited to participate. Patients were examined by a specialist and followed longitudinally to permit diagnostic review.

Results: we identified 257 potential cases, of whom 181 had suspected idiopathic Parkinson's disease. After a follow-up period of 18 months, 155 patients retained a clinical diagnosis of probable Parkinson's disease. The mean age at diagnosis was 72.4 ± 10 years. The crude incidence of PD in Newcastle and Gateshead was 15.9 per 100 000 persons per year (95% CI: 13.4-18.4). Age-standardised to the European population the incidence of Parkinson's disease was 12.0 per 100 000 (95% CI: 10.1-14.0). We found a higher crude incidence among men 17.7 per 100 000 (95% CI: 14.0-21.4) than women 14.0 per 100 000 (95% CI: 10.7-17.4).

Conclusion: in this prospective longitudinal study, the incidence rate of Parkinson's disease in North-East England is similar to that of other modern European and American studies.