The epidemiology of PSP.

The age-adjusted prevalence of PSP as measured in central New Jersey is 1.5 cases per million population, about 1% of that of Parkinson's disease. It incidence is 3-4 new cases per million population per year, similar to that of such better-known illnesses as myasthenia gravis, the hereditary ataxias as a group and Tourette syndrome. Median actuarially adjusted survival after symptom onset is 5.9-6.9 years. PSP appears to favor no geographical, racial, ethnic or occupational group, though there is anecdotal evidence for hydrocarbon exposure as a candidate etiologic factor. No familial cases of typical PSP have been proven. The one formal case-control study failed to implicate any particular causal agent and the rural predilection of PD appears to be absent in PSP. Better diagnostic methods, more multi-center organization, additional case-control studies and new etiologic hypotheses are needed in the epidemiological investigation of PSP.