Parkinson's disease epidemiology in the Northampton District, England, 1992.

In a population of 302,000, in a Midlands district of England, the estimated prevalence of idiopathic Parkinson's disease (IPD) increased from 108 to 121 per 100,000 from 1982 to 1992. Individual general practice prevalence ranged quite widely. Webster ratings were significantly more often scored in 1992, but at a lower level of severity, suggesting earlier diagnosis. Incidence in 1992 was estimated as 12 per 100,000 per annum. Micrographia, when copying interlocking pentagons, was significantly related to Hoehn & Yahr scores. Over the 10-year period, there has been a considerable change in prescribing: a positive response to medication was confirmed as a good diagnostic indicator. Progression of symptoms and an increase of physical disability was noted in those of the 1982 study alive in 1992.