The risk for people with Parkinson’s disease to develop dementia may be lower than previously thought, or dementia may occur later in the course of the disease than previously reported, a new study finds.
The report was published Wednesday in Neurology.
“The development of dementia is feared by people with Parkinson’s, and the combination of both a movement disorder and a cognitive disorder can be devastating to them and their loved ones,” Daniel Weintraub, MD, a researcher from the University of Pennsylvania in Philadelphia, said in a statement. “These results provide more hopeful estimates of the long-term risk of dementia for people with Parkinson’s disease, suggesting that there is a longer window to intervene to prevent or delay cognitive decline.”
Earlier research showed that about 80% of people with Parkinson’s disease would develop dementia within 15 to 20 years after receiving a Parkinson’s disease diagnosis.
“While these studies were important in highlighting the issue of cognitive decline in Parkinson’s disease, the studies were conducted many years ago, were relatively small and had other limitations, so we wanted to re-evaluate these findings,” Weintraub said.
Investigators evaluated two large prospective studies. One involved 417 participants, with an average age of 62, who were newly diagnosed with Parkinson’s disease and had not yet received treatment for the disease when the study began. The second study involved 389 people with Parkinson’s disease, with an average age of 69, who had been diagnosed with Parkinson’s an average of six years before the start of the study.
In the first study, the estimated probability of being diagnosed with dementia 10 years after being diagnosed with Parkinson’s disease was 9%. The second study found that the probability of being diagnosed with dementia 10 years after a Parkinson’s diagnosis was 27%. In that second study, the team found a 50% estimated higher risk of dementia 15 years after a Parkinson’s diagnosis and 74% higher risk 20 years after diagnosis.
