Tardive Dyskinesia - Epidemiology
Identifying the exact number of people affected by TD is difficult because of factors such as fluctuation in symptoms and the use of drugs that can mask or hide TD symptoms, thereby causing an underestimation of the true number of affected people. The estimated prevalence of TD varies greatly, from 0.5% to 65%, in accordance with the population being studied. Factors affecting the rate include age of the population, the DRA being used, the definition of TD being employed in the study, and the design of the study.
The rate of TD increases with age (50% in a group of elderly schizophrenic patients), as does the rate of spontaneous dyskinesias. In one study, 19% of young adults were found to have TD after five cumulative years of exposure to a neuroleptic drug. According to a review of more than 39,000 patients exposed to neuroleptic agents, Yassa and Jeste identified a mean prevalence of 24.2%, with a significantly higher prevalence in women (26.6%) than in men (21.6%); however, Lauterbach et al. found no difference in the incidence between sexes. Kane et al. found a cumulative incidence of 5% at one year, 10% at two years, 15% after three years, and 19% after four years of exposure to DRAs.