Cognitive Rehabilitation in PD Helpful but Needs to be Tailored, Review Says

A recent study examined the effect of cognitive rehabilitation in Parkinson disease (PD), which includes both motor and nonmotor symptoms.

Almost 30% of patients with PD, who do not have dementia, are still affected by mild cognitive impairment (MCI), including problems with attention, processing speed, working memory, set-shifting, and planning, as well as issues with visuospatial abilities, memory, or language. Medications used to ease motor symptoms, such as levodopa, or procedures such as deep brain stimulation, are not effective in treating impairments in cognition.

A previous meta-analysis on cognitive rehabilitation in PD reported mixed results. A more recent review included studies in patients who had both dementia and PD, making the comparison more difficult, because the aim of cognitive trainings in these 2 groups of patients are very different. In PD with MCI, the goal is to slow the slide into dementia, and in those with dementia, the goal is to stimulate activity and prevent further decline.

The authors of the current study sought to understand if cognitive rehabilitation works in patients with MCI and more specifically, which cognitive domains gain the most benefit. The authors analyzed behavioral outcomes for each cognitive domain separately.

The authors searched Cochrane, EMBASE, SCOPUS, and PubMed for studies published between January 2000 and September 2020 about cognitive rehabilitation in PD. To be included, studies had to investigate changes in cognitive tests in patients with PD and MCI before and after an intervention compared with a control treatment.

Individual cognitive trainings had to number at least 10 total sessions. In addition, studies had to be at least single blind and have a sample size of 20 or more. Studies were also assessed for risk of bias through the use of the Cochrane tool.

Cognitive outcomes were assessed for these domains: global cognition, executive function, attention, short-term and long-term memory, language, visuospatial processes, and clinical scales.

Means and standard deviations were extracted for each outcome before and after the intervention, and analyses were performed using R Studio 4.0.2. Heterogeneity was assessed using the total Cochrane Q test (Q), which evaluates if the variability among effect sizes is greater than expected.

After an initial retrieval of 172 studies, 14 were included in the final analysis, with a total of 767 participants. Studies reporting several cognitive tests for each domain were considered separately.

Researchers found that cognitive training worked well for some domains, but not others. Specifically, global cognition, executive functioning, and long- and short-term memory all benefitted from rehabilitation.

The researchers noted that “improving global cognition is one of the main goals of each cognitive rehabilitation.” They pooled data from 5 studies dealing with cognition, and after conducting an analysis, they found a significant difference in favor of rehabilitation programs.

For executive function, data were pooled from 9 studies. For short- and long-term memory, data were pooled from 7 and 8 studies, respectively. These studies also found a statistically significant difference in favor of cognitive rehabilitation.

But in line with previous studies, the researchers did not find improvement in attention, visuospatial abilities, or clinical scales. None of the individual studies in attention found statistically significant results.

A limit of the study is that 2 of the studies included in the analysis did not explicitly state that patients with dementia were excluded with the study. In addition, the small sample size and high heterogenicity limit the analysis; the issues could be addressed through a more controlled clinical trial, the authors said.

The results of the study show that some cognitive deficits in PD improve and that the cognitive rehabilitation should occur, with the understanding that not all domains might benefit.

The authors called the results “encouraging” and said that they “highlight the pivotal role that cognitive rehabilitation might play in PD.” But they also noted that studies with larger samples are required.

Reference

Andreina G, Lorernza M, Laura D, Elena R, Francesca B. Effects of cognitive rehabilitation in Parkinson disease: a metaanalysis. Neurol Sci. Published online January 31, 2022. doi:10.1007/s10072-021-05772-4