Recent trend on the prevalence of tardive dyskinesia in Japan.

An epidemiological study was undertaken, taking a survey of 2,274 chronic schizophrenic patients hospitalized for 2 years or more in 17 mental institutions in Japan. The overall prevalence of tardive dyskinesia (T.D.) was 19.1%. The prevalence of TD differs considerably from one institution to the other, with a range of 0 to 36.1%. The longer the history of institution was, the higher the prevalence of TD. The prevalence showed a tendency to increase with increasing age. Long-term hospitalization concomitant with continuous neuroleptic medication seemed to play a role in the prevalence of TD. TD occurred with higher frequency in patients with somatic complications than in those without complications. Past drug history, including duration of treatment and responsible neuroleptics, has been considered to play an important role in the prevalence of TD. But, results of the present investigation showed that the present drug status might also influence on the appearance of TD. The facts obtained from the present study are of value to establish regimens mainly based on medical treatment for prediction and prevention of TD.