Predictors of neuroleptic-induced dyskinesia and parkinsonism: The influence of measurement methods and definitions

The accurate and objective measurement of abnormal, involuntary movements remains highly desirable, whether the movements are secondary to pharmacotherapy or an expression of the primary illness. In a previous study, we found that the prevalence of tardive dyskinesia in a sample of 100 subjects ranged from 28% when using the Abnormal Involuntary Movement Scale (AIMS) or the Dyskinesia Identification Scale, Condensed User Version (DISCUS) to 62% using an instrumental measurement (IM) of peripheral dyskinesia. The goal of this study was to examine the relationship between various risk factors for tardive dyskinesia as predictor variables, and the AIMS, DISCUS, and IMs of dyskinesia, tremor, and velocity of motor movement as dependent variables. The sample consisted of 100, mostly patients with schizophrenia. Poor performance on the Mini-Mental State Examination (MMSE) and increasing age were the most consistent predictors of dyskinetic and parkinsonian movements. Various predictors were associated with specific abnormal movements. Head injury was related to slower speed of motor movements and the total DISCUS score. A history of smoking was associated with less IM dyskinesia. For those with coexisting parkinsonism and dyskinesia, significant associations were found with head injury, diabetes mellitus, and an AIMS score of 2 or greater in 2 body areas. Various classes of psychotropic agents seemed to have little influence on the MMSE or the development of dyskinesia and parkinsonism. Increasing age and a lower score on the MMSE seem to be particularly helpful in gauging the risk for parkinsonian and dyskinetic movements.