High incidence of tardive dyskinesia in older outpatients on low doses of neuroleptics.

We are conducting a prospective study of tardive dyskinesia (TD) in psychiatric patients over age 45, a large proportion of whom have had less than 1 month of total lifetime neuroleptic exposure. Patients are treated with the lowest effective dose of either haloperidol (usually 1-3 mg daily) or thioridazine (usually 25-75 mg daily). Patients are reexamined 1 month and 3 months after initial assessment and then at 3-month intervals. To date, a total of 68 patients (mean age 69.5 years) have been evaluated. Survival analysis showed a 27 percent cumulative incidence of TD (the 95% confidence interval being 14% to 40%) with 6 months of neuroleptic treatment in the study. The TD and non-TD patients did not differ on demographic and baseline clinical measures. Instrumental assessment showed that a greater proportion of TD patients had subclinical evidence of dyskinesia prior to the institution of neuroleptics, compared with non-TD patients.