A meta-analysis of prospective studies with schizophrenia patients was conducted to examine whether the evidence exists for risk factors for the emergence of Tardive Dyskinesia (TD) in schizophrenia. A computer assisted Medline/PubMed and Embase search was conducted in January 2008 for the years 1985-2007. Selected were truly prospective studies of incident cases of TD in a population with at least 80% patients with schizophrenia. Measures of relative risk were collected from the individual studies, either directly or by calculating the relative risk from the cox- or logistic regression coefficient provided in the article. Hazard Ratio's and Odds Ratio's were pooled using fixed and random effect models in case of multiple studies using the same measure of risk and outcome. Only eight studies satisfied the inclusion criteria reporting on 25 different single estimate risk factors. Of 25 risk factors, six concerned replicated estimates suitable for meta-analysis. Of these, non-white ethnic group and early extrapyramidal symptoms qualified as risk factors for the emergence of TD in schizophrenia. The association with older age was suggestive but inconclusive. Despite many reported risk factors for TD in schizophrenia, little conclusive evidence exists to corroborate this. However, the fact that early EPS predicts onset of TD has important clinical and research implications.
(c) 2009 Movement Disorder Society.