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Not all that moves is tardive dyskinesia
1Neuropsychiatry Branch, NIMH Neuroscience Center, St. Elizabeths Hospital, Washington, DC 20032.
Objective:
Because tardive dyskinesia and spontaneous dyskinesia appear the same, it is difficult to determine whether an individual patient's abnormal movements are induced by medication or have developed spontaneously. Therefore, estimates of the prevalence of tardive dyskinesia that are based on observations not adjusted for spontaneous dyskinesia are inflated. In addition, age is thought to be an important risk factor in the development of both tardive and spontaneous dyskinesias. The authors estimate the prevalence of both disorders for specific age groups.
Method:
The authors reviewed nine reports on dyskinesia prevalence that included history of neuroleptic treatment and related prevalence to age. A rating of 2 or more on the Abnormal Involuntary Movement Scale or an equivalent score on another scale was considered an indication of dyskinesia. If the subject had taken neuroleptics for more than 3 months, the movement disorder was classified as neuroleptic-associated dyskinesia; other dyskinesias were considered spontaneous. The prevalence of tardive dyskinesia was defined as the rate of neuroleptic-associated dyskinesia minus the rate of spontaneous dyskinesia.
Results:
The true rate of tardive dyskinesia was below 20% for all age groups except 70-79 years. The correlation between the rate of neuroleptic-associated dyskinesia and the rate of spontaneous dyskinesia was low.
Conclusions:
After age 40 the prevalence of spontaneous dyskinesia is sufficiently high to conclude that many patients with diagnoses of tardive dyskinesia have abnormal movements attributable to causes other than neuroleptics.
Insights
Differentiating tardive dyskinesia from spontaneous dyskinesia is challenging. After age 40, spontaneous dyskinesia prevalence is high, meaning many diagnosed with tardive dyskinesia may have other causes for abnormal movements.
Area of Science:
- Neurology
- Psychiatry
Background:
- Tardive dyskinesia (TD) and spontaneous dyskinesia (SD) present similarly, complicating diagnosis.
- Accurate TD prevalence estimates require adjustment for SD, as unadjusted figures are inflated.
- Age is a significant risk factor for both TD and SD.
Purpose of the Study:
- To estimate the prevalence of TD and SD across different age groups.
- To differentiate medication-induced movements from spontaneous movement disorders.
Main Methods:
- Reviewed nine prevalence studies on dyskinesia, correlating findings with age and neuroleptic treatment history.
- Defined dyskinesia by a score of ≥2 on the Abnormal Involuntary Movement Scale (AIMS) or equivalent.
- Calculated TD prevalence as the rate of neuroleptic-associated dyskinesia minus the rate of SD.
Main Results:
- True TD prevalence was under 20% for most age groups, with an exception in the 70-79 age range.
- A low correlation was observed between the rates of neuroleptic-associated dyskinesia and SD.
Conclusions:
- Spontaneous dyskinesia prevalence increases significantly after age 40.
- A substantial proportion of individuals diagnosed with TD after age 40 may have abnormal movements due to non-neuroleptic causes.