Fluctuations in attention. PD dementia vs DLB with parkinsonism.
Ballard CG, Aarsland D, McKeith I, O’Brien J, Gray A, Cormack F, Burn D, et al.;
Commented by , 28 Jan 2003
Aim of the study
Establish if a distinction can be made between Parkinson’s disease (PD) with or without dementia and Dementia with Lewy Bodies (DLB) with or without parkinsonism, in regard to fluctuations in attention and cognitive reaction time.
Method
Clinically diagnosed patients from tertiary referral clinics in the United Kingdom and Norway, were studied with the Cognitive Drug Research computerized battery. Clinical groups included
- 50 elderly controls
- 50 PD without dementia
- 48 PD with dementia
- 50 DLB with or without parkinsonism
- 80 Alzheimer’s disease (AD)
The operational distinction between PD dementia and DLB with parkinsonism is one year or longer occurrence of parkinsonism before the onset of dementia.
Results
Impairments in reaction time, vigilance, and fluctuating attention were comparable in patients with PD dementia and DLB, although to a lesser degree in patients with DLB without parkinsonism.
Patients with PD but no dementia did not exhibit fluctuation of attention, but had significantly greater impairment of cognitive reaction time than elderly controls, and comparable impairment to patients with AD.
The profile of attentional impairment and fluctuating attention is thus similar in PD dementia and DLB with parkinsonism, and the current arbitrary distinction between these patients groups is not supported by these findings.
Discussion
These results have a number of implications for clinical research, since a number of randomized clinical trials (RCT) comparing cholinesterase inhibitors to placebo are underway in PD dementia. The diagnostic criteria for PD dementia are still in need of an evidence-based consensus approach similar to the research criteria for AD and DLB.
The primary and secondary outcomes for RCT in PD dementia are still evolving: the evidence for fluctuations in attention as well as in cognitive reaction time provided in this article will be useful in this regard.
It is of interest that the Food and Drug Administration raised concerns about the ability of clinicians to diagnose DLB: it is fortunate that there are more similarities than differences between DLB and PD dementia, the latter being common knowledge among physicians who care for patients with PD over the later stages, where the emergence of dementia and worsening of motor symptoms and signs are both increasing the risk of mortality (Levy et al, Neurology 2002, 59, 1708-1713).
As far as clinical applicability of these findings is comcerned, the lack of fluctuating attention in patients with PD but no dementia will be somewhat reassuring in terms of their ability to drive, an issue regularly discussed in the medical literature (latest article: Zesiewicz et al, Neurology 2002; 59: 1787-8).
Furthermore the computerized battery of attention tasks could be completed in 15 minutes and by patients with MMSE scores below 10, suggesting that it could be used as a component of clinical workup in specialized clinical practice, including Movement Disorders Clinics.