Comparison of the prevalence of Parkinson's disease in black populations in the rural United States and in rural Nigeria: door-to-door community studies.

A door-to-door survey of Parkinson's disease (PD) in Copiah County, Mississippi, using a pretested screening procedure (with a high sensitivity for detecting PD), followed by examination of all positives by a senior neurologist, revealed similar prevalence ratios for blacks and whites. The same procedure was applied in the community of Igbo-Ora, Nigeria, a black population of West Africa. To assure uniformity in the procedures and application of the diagnostic criteria, a neurologist from each survey site visited the other site. Among a black population of 3,521 over age 39 in Copiah County, there were 12 cases of PD, with an age-adjusted prevalence ratio of 341/100,000. The comparable figures for Igbo-Ora were as follows: population over age 39 = 3,412; cases of PD = 2; age-adjusted prevalence ratio = 67/100,000.