To compare quantitative and qualitative aspects of neuropsychological test performance in patients with Parkinson's disease who currently had depression (PDD) and those without depression (PDN) so as to evaluate the influence of depression on cognition in Parkinson's disease.
Cross-sectional comparisons among PDN, PDD, and normal control (NC) groups. The setting was a neurodegenerative disease research center in a teaching hospital. Groups consisted of 44 patients with PDN and 44 patients with PDD matched for age, education, gender, age at onset of disease, disease duration, and disease severity; a group of 44 NC subjects matched for age, education, and gender; and a second set of comparisons between 15 patients with PDN and 15 patients with PDD also matched for overall severity of cognitive impairment.
The neuropsychological measures used were the Mattis Dementia Rating Scale, Beck Depression Inventory, Wisconsin Card Sorting Test, Controlled Oral Word Association Test, Logical Memory subtest of the Wechsler Memory Scale—Revised, Digit Span subtest of the Wechsler Adult Intelligence Scale—Revised, and the Boston Diagnostic Aphasia Examination's Animal Naming test and Boston Naming Test.
Relative to the NC group, both PDN and PDD groups demonstrated impairments in immediate and delayed verbal recall, semantic fluency, and problem solving. When PDN and PDD groups were matched for demographic and disease variables, only the PDD group evidenced impairment relative to NC in visual confrontation naming, and in lexical and semantic fluency. In addition, impairments on immediate recall and semantic fluency in the PDD group were more pronounced than those in the PDN group. However, when PDN and PDD groups were also matched for overall severity of cognitive impairment, no significant differences emerged among the two groups' neuropsychological test performances.
Depression exacerbates some memory and language impairments associated with PD, even when the PDN and PDD groups are matched for demographic and disease variables. However, the extent and pattern of cognitive impairment is similar in PDN and PDD when the groups are also matched also for overall severity of cognitive impairment. Depression influences the quantity rather than the quality of cognitive impairment associated with Parkinson's disease.