Parkinson’s disease is a neurodegenerative disorder affecting 1% to 2% of people age 60 and older. Although Parkinson’s disease has been widely regarded as a motor disorder, it is now accepted that cognitive decline is also a core feature of the disease, impacting the quality of life of 60% to 80% of patients, in due course. 

While pharmacological treatment for motor symptoms of Parkinson’s disease has considerably improved, treatment for cognitive symptoms remains limited. Thus, cognitive training, involving guided practice of a set of structured, usually standardized, tasks designed to train individuals on relatively well defined cognitive processes and abilities, has large potential clinical benefit for people with dementia or mild cognitive impairment. 

To determine whether cognitive training improves cognition in these patients, Orgeta and other authors recently conducted a Cochrane Systematic Review, including only studies where patients with dementia or mild cognitive impairment related to Parkinson’s disease were randomly allocated either to cognitive training (intended to train general or specific areas of cognitive function, targeting either a single domain or multiple domains of cognition) or to a control intervention. 

Only seven studies with a total of 225 participants met the inclusion criteria for this review. In all of them, cognitive training was delivered by computer, lasting four to eight weeks. Comparison included no intervention or recreational activities, speech or language exercises, computer-based motor therapy, or motor rehabilitation combined with recreational activity. 

Overall, although cognitive training was associated with higher scores on global cognition, attention, and verbal memory at the end of treatment, the result was imprecise and not statistically significant. No evidence of difference at the end of treatment between cognitive training and control interventions was found for executive function or visual processing, and no evidence of effects of cognitive training on activities of daily living or quality of life was found. 

Research gaps are wide, as results are based on a small number of studies with few participants, limitations of study design and execution, and imprecise results, providing only low-certainty evidence; further, the search could not include any study assessing face-to-face cognitive training, and included only one study focusing on Parkinson’s disease dementia. Thus, large-scale, well designed clinical trials are urgently needed before we can be confident on whether cognitive training is effective or not for cognitively impaired Parkinson’s disease patients. 

Commented by Francesca Cecchi