Prevalence of multiple sclerosis: a door-to-door survey in Lan Cang La Hu Zu Autonomous County, Yunnan Province of China.

A door-to-door survey of major neurological disorders was conducted in Lan Cang La Hu Zu autonomous county, Yunnan province of China. A total of 47,825 individuals was sampled at random from a well-defined population of 424,628, including two ethnic groups, La Gu (60%) and Han (40%). On the basis ofthe research protocol provided by the World Health Organization, we administered a symptom questionnaire and a brief neurological examination to all subjects in the sample on December 31, 1986, prevalence day. Each subject who screened positive for movement disorders or reported a diagnosis of multiple sclerosis (MS) was extensively investigated by four neurologists, using standardized diagnostic criteria. Only one instance of clinically definite MS was identified on prevalence day, yielding a point prevalence ratio of 2.1 /100,000 population. The age-adjusted prevalence ratio (to US 1970 population) was 1.4/100,000 with 95% confidence limits of 0 and 8. This observed prevalence ratio of MS in Lan Cang La Hu Zu autonomous county, Yunnan province of China, falls in the low MS frequency zone (under 5/100,000). It is similar to other MS prevalence ratios reported from Asia and Africa save for the English-speaking white group in South Africa among whom MS prevalence is somewhat higher.