Background: Although newly emergent tardive dyskinesia (TD) is less of a concern, about one-fourth to one-third of patients on or previously on chronic first-generation antipsychotic agents have TD. The long-term course and outcome, as well as their predictors, are unknown. Earlier studies identify ethnicity as one of the risk factors for the development of TD, and case reports have noted a preponderance of African-American males in cohorts of patients with tardive dystonia. The current study examines the anatomic distribution and course of TD in a cohort of schizophrenia patients of European and African descent with TD who were referred to the Motor Disorders Clinic (MDC).
Methods: We evaluated data collected on 1149 TD patients who were given a focused neurologic examination for movement disorders. Movements were evaluated with the MPRC Scale for Involuntary Movements (IMS). All patients met RDC-TD criteria for diagnosis of persistent TD. One to 10-year follow-up data on 528 patients were evaluated to examine the course of TD following recommendations made to referring primary clinicians. Suggested interventions to referring primary clinicians included dose reduction of first-generation antipsychotic medication, or switching to a second-generation antipsychotic.
Results: Initial evaluation included 701 European American (EA) patients and 448 African-American (AA) patients. AA patients had a significantly higher proportion of males [chi(1) = 7.50, P < 0.05]. EA subjects had a higher mean age than AA patients 42.8 +/- 11.2 and 39.8 +/- 10.4, respectively [F(1,1147) = 22.27, P < 0.05]. Mean neuroleptic exposure (chlorpromazine equivalents) was similar in both groups after controlling for differences in age.Follow-up data analyzed in 528 patients (329 EA and 199AA) showed a significant ethnicity by TD interaction [F(1,504) = 4.26, P < 0.05]. Examination of body distribution of dyskinetic movements showed an effect of ethnicity. Subsequent analyses suggest EA patients experienced more improvement in TD over the course of follow up [F(1,319) = 22.39, P < 0.05] compared with AAs [F(1,189) = 1.58, P > 0.05]. These findings were unchanged when age, change in antipsychotic drug dose, and duration of follow-up were covaried.
Conclusion: Reports from earlier studies note ethnicity (African descent) as a risk factor in the development of TD. Our study findings suggest ethnicity might be an important factor in predicting a poor course of TD.