Verbal fluency in Parkinson's disease

This study compares the performance of Parkinson's disease patients with age-matched controls on semantic and letter-initial verbal fluency tests. An analysis of variance revealed that Parkinsonian patients showed impaired word production. However when the covariates of age, present verbal ability (Mill Hill Synonyms) and severity of depression (Geriatric Depression Screening Scale) were included in an analysis of covariance, the significant effect of Parkinson's disease on verbal fluency disappeared. Instead, age and present verbal ability were revealed to be the significant sources of between subject variation in total verbal fluency performance; results indicated that increased age and lower present verbal ability resulted in poorer performance on the verbal fluency tests. Depression score was not a significant source of between subject variation. The results are discussed in relation to those recently reported by Gurd and Ward (1989).