Instrumental evidence that age increases motor instability in neuroleptic-treated patients

Fine control of isometric finger flexion force was measured to evaluate motor instability in 40 schizophrenic/schizoaffective patients exposed to neuroleptics and 43 age-comparable normal controls without prior neuroleptic exposure. All the subjects were free of idiopathic or neuroleptic-induced movement disorders. Older neuroleptic-treated patients exhibited significantly greater instability of isometric force compared with older controls, younger patients, or younger controls. Our study indicated that advanced age and neuroleptic exposure contributed to significantly greater motor instability than would be expected by advanced age or neuroleptic exposure alone. These findings are discussed as they pertain to potential mechanisms underlying neuroleptic-induced extrapyramidal side effects.