Survey of major neurologic disorders in a biracial United States population: the Copiah County Study.

To determine the prevalence of frequently occurring neurologic disorders in a biracial population, a survey of households and chronic care institutions was carried out for all residents of Copiah County, Mississippi. Along with a complete census, interviews were held using extensive questions about diagnoses, signs, and symptoms of neurologic disorders. More than 97% of eligible households participated, comprising 23,842 persons (49% black, 50% white, 1% other). Persons with responses suggesting one or more of these disorders were examined by a neurologist who used defined diagnostic criteria. Age-adjusted prevalence ratios for cerebral palsy, epilepsy, stroke, and severe dementia were somewhat higher in blacks than in whites, while the age-adjusted prevalence ratio for essential tremor was slightly higher in whites. For Parkinson's disease, there was no difference in age-adjusted prevalence ratios between the races.