Many people with Parkinson’s disease may fear dementia as a common consequence of the disease.

But new research suggests dementia is not inevitable with Parkinson’s, and in fact is less common than presumed.

If dementia does occur, it typically does so much later in life than was previously assumed, the study also found.

“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,” said study lead author Dr. Daniel Weintraub, of the University of Pennsylvania (UPenn) in Philadelphia.

The findings were published Aug. 7 in the journal Neurology.

As Weintraub noted in a journal news release, “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.”

Prior studies had suggested that 80% of Parkinson’s patients might develop dementia within 15 to 20 years of being diagnosed with Parkinson’s.

“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,” noted Weintraub, an assistant professor of psychiatry at UPenn.

To get a clearer picture of the incidence of dementia among Parkinson’s patients, Weintraub’s team analyzed data from two large, prospective studies.

One study involving 417 people was international. Participants averaged 62 years of age, were newly diagnosed with Parkinson’s as they entered the study, and had not yet begun treatment at the study’s inception.

The second study was based at UPenn. It involved 389 Parkinson’s patients averaging 69 years of age. All had been diagnosed with the illness about six years before they joined the study.

Folks in the international study were tracked for 10 years, and over that time an estimated 9% went on to develop dementia, Weintraub’s team noted.

For the Pennsylvania study, in which patients skewed older, an estimated 27% of patients went on to develop dementia over a 10-year span. Estimated 15-year risks for dementia in this study were 50% and the risk rose to 74% over 20 years, the researchers said.

Being older, male and having a lower level of education were all factors upping the odds for dementia.

The researchers noted that participants in the studies tended to be highly educated white people, so the findings may not apply to the general population.

More information

Find out more about Parkinson’s disease at the Parkinson’s Foundation.

SOURCE: American Academy of Neurology, news release, Aug. 7, 2024

Source: HealthDay