Subtypes of mild cognitive impairment in Parkinson's disease: progression to dementia.

The aim of this study was to establish the rate of progression from mild cognitive impairment (MCI) to dementia in patients with Parkinson's disease (PD). PD patients without dementia were recruited in 1997 from an ongoing prospective epidemiological study. The assessment included neurological and psychiatric examinations, a clinical interview based on the Diagnostic and Statistical Manual of Mental Disorders, Revised Third Edition (DSM-III-R) criteria for dementia, and a battery of neuropsychological tests. PD was diagnosed according to established criteria, dementia was diagnosed according to the DSM-III-R criteria, and subtypes of MCI were classified according to modified Petersen's criteria. Seventy-two nondemented PD patients were included. A total of 34 were cognitively intact, whereas 38 were diagnosed with MCI (amnestic, n = 6; single nonmemory domain, n = 17; multiple domains slightly impaired, n = 15). Fifty-nine patients (82%) completed follow-up examination 4 years later, and 18 (62%) of the patients with MCI and 6 (20%) of the cognitively intact PD patients were demented (P = 0.001). Single domain nonmemory MCI and multiple domains slightly impaired MCI were associated with later development of dementia (P = 0.003; P = 0.04), whereas amnestic MCI subtype was not (P = 0.76). We conclude that patients with PD and MCI had a higher risk of developing dementia than cognitively intact PD patients, suggesting that MCI in PD is an early manifestation of dementia. However, these findings should be interpreted with caution due to the relatively small number of subjects included in this study.

Cognitive profiles of individual patients with Parkinson's disease and dementia: comparison with dementia with lewy bodies and Alzheimer's disease.

We describe the pattern of cognitive profiles within a community-based sample of patients with Parkinson's disease (PD) and dementia (PDD) using cluster analyses, and compare the results with data from patients with Alzheimer's disease (AD) and dementia with Lewy bodies (DLB). Fifty patients with PDD and 39 with AD from Stavanger, Norway, and 62 patients with DLB from San Diego, CA, USA were diagnosed by either standardized clinical procedures or criteria (all PDD and all AD cases) or necropsy (all DLB cases). Four subgroups were identified: two subgroups with a subcortical cognitive profile (one with mild and one with moderate dementia severity), one subgroup with global impairment and severe dementia, and one subgroup with a cortical cognitive profile and moderate dementia. Of the patients with PDD and with DLB, 56% and 55%, respectively, had a subcortical cognitive profile, compared with only 33% of the AD patients. Conversely, 30% of the patients with PDD and 26% of those with DLB had a cortical cognitive profile, compared with 67% of the patients with AD. These findings suggest that in some patients with PDD, frontosubcortical changes are the main contributing factor to dementia, whereas in other patients, cortical and hippocampal changes are more important.

Cognitive predictors of dementia in Parkinson's disease: a community-based, 4-year longitudinal study.

Although mild cognitive impairment and dementia are common and have important clinical consequences for patients with Parkinson's disease (PD) and their caregivers, it is still unclear whether cognitive symptoms may predict the development of dementia in PD patients. The objective of this study was to determine whether cognitive deficits in nondemented PD patients predicted the development of dementia 4 years later. A total of 76 nondemented PD patients from an epidemiological study of PD in the county of Rogaland, Norway, were assessed at baseline and 4 years later with neurological, psychiatric, and neuropsychological evaluations. Twenty-five (42%) new cases of dementia were diagnosed after 4 years. Time to complete the third card of the Stroop test was the only variable that was independently associated with dementia. The authors concluded that poor performance on a test sensitive to executive dysfunction predicted later development of dementia in PD patients. This finding may have important clinical implications as a marker of subsequent development of dementia.