"[The finding's] value in predicting Parkinson's disease dementia is less clear and needs further research," Copeland said.
To map the course of thinking problems in Parkinson's patients, Pedersen's team followed 182 patients for three years. Participants completed a battery of screening exams, including tests of their memory, verbal fluency and color-naming ability.
During the study, 27 percent of patients who had thinking problems at diagnosis went on to develop dementia, compared with 0.7 percent of those who didn't have thinking problems, the researchers said.
For some patients, however, normal thinking returned. Among those with thinking problems, about 19 percent saw their thinking problems clear up, Pedersen's group found.
The progression to dementia was also dependent on how severe the patient's thinking problems were, the researchers noted.
Among patients with the most severe thinking problems at the start of the study and one year later, 45.5 percent went on to develop dementia while only about 9 percent saw their thinking restored to normal, the researchers said.
Although the study found an association between mild thinking problems in patients newly diagnosed with Parkinson's disease and later dementia, it did not establish a cause-and-effect relationship.
To learn more about Parkinson's disease, visit the U.S. National Institute of Neurological Disorders and Stroke.
SOURCES: Kenn Freddy Pedersen, M.D., Ph.D., Norwegian Center for Movement Disorders, Stavanger University Hospital, Norway; Brian Copeland, M.D., Movement Disorder Fellow, University of Texas Medical School at
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