[Tardive dyskinesia in patients with schizophrenia treated with olanzapine - results from a 20-month, prospective, open study under naturalistic conditions].
OBJECTIVES
The objective of the study was to assess the prevalence and incidence of tardive dyskinesia in patients treated with olanzapine during the follow-up period of 20 months.


METHODS
It was a prospective, observational, non-interventional study under naturalistic conditions, without a control group. The evaluation of the severity and presence of tardive dyskinesia was performed with the Abnormal Involuntary Movement Scale and research criteria by Schooler and Kane.


RESULTS
The study included 573 patients (woman 43,3%) with the diagnosis of schizophrenia (ICD-10), the mean age of 41.8 (± 12) years. The mean dose of olanzapine was 15.9 (± 4.2) mg. The prevalence of tardive dyskinesia was 16.4%. The cumulative incidence assessed in the group of 479 patients was 6.47%. The annual incidence was 3.9%. An increased risk of tardive dyskinesia was observed in smokers - RR of 1.99 (CI 0.88-4.49), those taking higher doses of olanzapine 1.57 (CI 0.91-2.7) and in those who used polytherapy: 3.55 (CI 1.43-8.82). Only in the case of polytherapy a multidimensional analysis confirmed that this factor had a significant influence on the risk of tardive dyskinesia (p=0.006).


CONCLUSIONS
The study demonstrated high (16,4%) prevalence of tardive dyskinesia, and the annual incidence (3,9%) comparable to the results of a meta-analysis by Corell et al. In the case of olanzapine in monotherapy the annual incidence was lower (1.96%) but the use of antipsychotics in polytherapy more than tripled the risk of tardive dyskinesia.