Cross sectional prevalence survey of idiopathic Parkinson's disease and parkinsonism in London

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Abstract
Full details of the methods have been reported elsewhere.5 Records from 15 practices in London (121 608 patients) were screened for a diagnosis of Parkinson's disease or parkinsonism; antiparkinsonian drugs; or mention of tremor after the age of 50 years. Diagnosis was based on clinical assessment (by AS), with a video recording for secondary confirmation (by NPQ). Idiopathic Parkinson's disease was diagnosed according to the criteria of the UK Parkinson's Disease Society Brain Bank,w1 with the exception that an isolated positive Babinski sign in an elderly patient with otherwise typical idiopathic Parkinson's disease was not considered to invalidate the diagnosis. Isolated classic resting tremor was considered to be “possible” Parkinson's disease. Multiple system atrophy and progressive supranuclear palsy were diagnosed according to published criteria.w2 w3 Vascular parkinsonism was diagnosed if at least two of the following were present: history of strokes, abrupt onset with stepwise progression, hypertension, a wide based gait with small steps, cognitive decline, pseudobulbar or pyramidal signs. Drug induced parkinsonism was diagnosed if a dopamine receptor blocking drug had been started within six months of the onset of symptoms and taken for at least six months. The date taken for calculating prevalence was 1 July 1997. We calculated crude prevalence rates and age adjusted rates by direct standardisation to the 1997 UK population, and a 95% confidence interval was calculated with Smith's method.w4