Greater apathy, depression at diagnosis tied to cognitive decline

Call for more research into factors affecting cognition in Parkinson's disease

Marisa Wexler, MS avatar

by Marisa Wexler, MS |

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People with Parkinson’s disease facing anxiety, depression, apathy, and other mental health challenges when diagnosed are more likely to experience a decline in their cognitive abilities with disease progression, a study reported.

“Considering the importance of cognitive dysfunction … it is critical to identify factors that could predict a faster rate of global cognitive decline [in patients], such as neuropsychiatric symptoms,” the researchers wrote, stressing a need for greater study.

The study, “Longitudinal cognitive changes in patients with early Parkinson’s disease and neuropsychiatric symptoms,” was published in CNS Neuroscience & Therapeutics.

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No link found with impulse control issues and changes in cognition

Cognitive impairment is a common nonmotor Parkinson’s symptom. However, not all patients experience cognitive problems, and specialists continue to note difficulties in predicting the risk of such problems when diagnosing the disease.

Psychiatric issues like anxiety, depression, apathy and psychosis, along with problems with impulse control, are other known nonmotor manifestations of Parkinson’s. Researchers in China analyzed data from the Parkinson’s Progression Markers Initiative (PPMI) — a research program aiming to contribute to disease diagnosis and treatment — to assess the relationship between cognitive impairment and psychiatric issues over time.

Their analysis included data covering 423 people with newly diagnosed Parkinson’s; 315 of them were followed for at least five years.

Over those years, 66 of these patients showed signs of cognitive impairment on standardized tests of cognition. Patients who developed cognitive issues also tended to have more severe motor symptoms when diagnosed, and they were disproportionately male.

Statistical analyses showed significant correlations between measures of cognitive impairment and assessments of anxiety, depression, psychosis, and apathy — meaning that patients who experienced these psychiatric issues also were more likely to experience cognitive problems. Anxiety and depression were particularly associated with poorer scores related to mental processing speed and memory, the researchers noted.

“Our study confirmed that [psychiatric problems], including depression, anxiety, and apathy and psychosis exhibit longitudinal relationships with [cognitive impairment] in [Parkinson’s] patients. These patients experienced greater rates of cognitive decline over time,” the scientists concluded.

The team noted that it’s not fully clear why these psychiatric problems tend to accompany cognitive impairment in Parkinson’s. The researchers speculated that damage to some parts of the brain may contribute to both cognitive and mental health challenges. But they stressed that further study is needed to understand the mechanisms underlying these Parkinson’s symptoms.

Among all psychiatric problems assessed, the only one not showing a significant association with cognitive impairment was impulse control disorders (ICDs).  Prior studies into the relationship between ICDs and cognitive impairment in Parkinson’s have conflicting results, the researchers noted.

“We found that ICDs were not associated with global cognitive decline and that patients with ICDs were not more likely to develop [cognitive impairment] in the PPMI cohort,” the team wrote. “Although our study sheds some light on this issue, there is a clear need for further investigation.”