Parkinson’s disease patients with mild cognitive impairment (MCI) have a lower quality of life if their memory is impaired, according to a study that also revealed that MCI is associated with more severe attention and memory dysfunction in people with the disease.
The study, “Mild cognitive impairment in Parkinson’s disease: Characterization and impact on quality of life according to subtype,” appeared in the journal Geriatrics & Gerontology International.
MCI is a major risk factor for dementia and is more prevalent in Parkinson’s patients than in the general population. The prognosis of MCI in Parkinson’s depends on its specific subtypes, which may affect at least five domains: language, memory, attention, visuospatial function, and executive function, the latter of which involves goal-directed actions and ability to adapt to new situations.
Early MCI in Parkinson’s is associated with older age, greater motor impairment, and depression. In addition, research has shown that older age, being male, and motor dysfunction all lead to a greater risk of developing dementia in this patient population. However, a more detailed understanding of MCI in Parkinson’s is needed to improve patient management.
To address this, Brazilian researchers characterized MCI as either amnestic or non-amnestic and assessed its impact on quality of life. For reference, amnestic MCI impairs memory, while non-amnestic MCI affects other domains, namely language, attention, visuospatial skills, and/or executive function.
All participants underwent a neurological examination and were also evaluated using four clinical scales: Modified Hoehn and Yahr scale (which assesses the progression of Parkinson’s symptoms), Unified Parkinson’s Disease Rating Scale (UPDRS), Parkinson’s Disease Quality of Life Scale (PDQ-39), and the Schwab-England Activities of Daily Living Scale.
The study included 149 participants — 60 Parkinson’s patients and 81 individuals used as controls — of whom 52 patients (86%) and 60 controls (74%) had MCI. Overall, patients and controls did not differ in assessments of depression and global cognition, as evaluated with the Mini-Mental State Examination.
Amnestic MCI was diagnosed in 29 patients (mean age 62.1 years, 58.6% men) and 35 controls (61.3 years, 54.3% women), while non-amnestic MCI was found in 23 patients (62.1 years, 58.6% men) and 25 controls (61.3 years, 76% women).
Amnestic and non-amnestic Parkinson’s patients showed no differences in Parkinson’s duration and severity. However, amnestic patients revealed greater impairment in activities of daily living, meaning a lower quality of life.
Impairment in multiple domains was more common than in a single domain in both patients and controls. Regarding the predominant motor sign in Parkinson’s patients, the pure akinetic-rigid form — slow movements and rigidity — was more frequent in non-amnestic (69.65%) than in amnestic (37.9%) patients, but this was not statistically significant.
Neuropsychological evaluations showed that the most useful tests to assess cognition and differentiate amnestic from non-amnestic MCI were the Figure Memory Test, which addresses visual perception, language, attention, recognition, as well as visual short-term, long-term and learning memory; the Rey Auditory Verbal Learning Test; and the Trail Making Test, which analyzes visual attention and task switching.
Parkinson’s patients had worse scores in all three tests than controls. While episodic memory and verbal memory/learning were more significantly impaired in non-amnestic and amnestic patients than in controls, the dysfunction in attention was more pronounced in amnestic Parkinson’s patients.
These findings also revealed that attention was the most significantly impaired domain in both patients and controls, followed by memory.
“These results reveal that the [Parkinson’s] group had worse cognitive performance,” the researchers wrote. A longitudinal analysis of these participants will enable them to determine whether Parkinson’s patients are at a higher risk for dementia and whether this risk is different between amnestic an non-amnestic patients.