Dementia not a given in decade after Parkinson’s diagnosis: Study
Condition may occur less often or later than generally believed
Most people with Parkinson’s disease don’t experience dementia in the first decade after diagnosis, a study reported.
The findings challenge long-held beliefs that dementia is a fairly common issue that tends to crop up early on in Parkinson’s patients. The study, “Long-Term Dementia Risk in Parkinson Disease,” was published 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, study co-author and professor of psychiatry at the University of Pennsylvania, said in a journal press release.
The 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,” Weintraub said.
Dementia —involving problems with cognition, memory and emotional regulation — can be a non-motor symptom of Parkinson’s. Previous studies have found that about four in five Parkinson’s patients will experience dementia within 15 to 20 years after receiving a diagnosis. But those studies were published more than 20 years ago and had limitations, the researchers said.
Window between Parkinson’s diagnosis and cognitive decline
While prior 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.
To get a better idea of the prevalence of dementia among Parkinson’s patients, the researchers analyzed data from two datasets: 417 patients in the Parkinson’s Progression Markers Initiative (PPMI), an international study collecting long-term outcomes for Parkinson’s patients, and a group of 389 patients who have been monitored at the University of Pennsylvania.
The PPMI analysis showed that 10 years after diagnosis, 9% to 15% of patients met the criteria for dementia. There was some variability depending on specific criteria used to define dementia, the researchers noted.
About one in four (27%) of the University of Pennsylvania patients had dementia 10 years after diagnosis. About half (47%) eventually developed dementia, but the median time to dementia was 15 years after diagnosis.
Combining data from both studies, the researchers estimated that about half of Parkinson’s patients will develop dementia 15 years post-diagnosis, and by 25 years post-diagnosis, about 90% of patients will have dementia. These rates are generally lower than previous estimates, the researchers said.
“Analyzing data from two large, prospective, ongoing observational [Parkinson’s] studies, we found that dementia may occur less frequently or develop over a longer period of time than has generally been assumed based on older studies,” the scientists concluded.
The results “provide updated, and more hopeful, estimates of long-term dementia risk in [Parkinson’s], suggesting a longer window to intervene to prevent or delay cognitive decline,” they wrote.
In further statistical analyses, the researchers found that the likelihood of developing dementia was greater among patients who were older when they were diagnosed, those who were male, and those with less formal education. All of these risk factors are consistent with previous studies, the scientists noted.
A limitation of the analyses is that both datasets involve white, well-educated patients, the researchers said. They stressed a need to verify the findings in more diverse populations.
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