Some people with Parkinson’s disease have cognitive abilities that remain stable over time, while others’ worsens, a new study finds. Early problems with visual processing and spatial reasoning are good indicators of cognitive impairments in the long run, data showed.
The study, published Aug. 5 in Annals of Neurology, also found that Parkinson’s patients with cognitive decline exhibit an increase in the power density of slow brain waves linked with sleep, which predicted worsening in different cognitive measures after two and four years of follow-up.
“Development of an aggressive cognitive decline in [Parkinson’s disease] is associated with increased slow-wave power density,” the researchers wrote.
The team assessed cognition in two groups of adults with Parkinson’s disease and compared them with healthy controls over a four-year period.
The first group included 82 people with Parkinson’s disease and 25 healthy controls, while the second group had 393 patients with the disease and 112 controls. Investigators used the Parkinson’s Disease-Cognitive Rating Scale (PD-CRS) to assess cognitive function. Blood tests, imaging tests and electroencephalogram (EEG) readings were also used along with assessments of memory, attention, language, visuospatial functions and executive function. The team checked in on people in the first group yearly; and with the second group at baseline, and then two and four years later.
In the first group, the team noted two distinct patterns of cognitive changes over time: In about 60% of patients, cognition remained stable or improved, while 40% had progressive cognitive decline.
Those with declining cognitive abilities had worse function after two years in the posterior cortex — the part of the brain that manages visual processing and spatial reasoning. The patients also showed worse frontal-subcortical functions, which include attention, memory, planning, and speech.
By the fourth year, people whose cognitive function declined also had worse motor symptoms day-to-day functionality compared with those who were stable.
Over the course of the four-year follow-up, those in the first group had a twofold increased risk of mild cognitive impairment and a 4.9 times higher risk for dementia; people in the second group whose function was declining had a 1.8 times greater risk of mild cognitive impairment and a 7.3 times higher risk for dementia.
“We were able to identify [two] distinct patterns of cognitive decline in [Parkinson’s disease],” the authors wrote. “Early changes in the performance pattern on specific posterior-cortical-dependent tasks, and early increases in [slow wave] power density in several … brain regions anticipate and predict the development of a more aggressive cognitive trajectory.” These results, they added, “underscore the importance of comprehensive cognitive and functional evaluations complemented by EEG data,” to help predict how a person’s abilities might change.
