A new study led by Mayo Clinic researchers has come up with a clearer and more practical way to define a rare and fast-moving form of dementia called rapidly progressive dementia, or RPD.
This serious brain condition causes thinking and memory problems that get worse much more quickly than typical dementia. While most dementias like Alzheimer’s develop slowly over many years, RPD can lead to major mental decline or even death within just one or two years.
Even though RPD only makes up about 4% of all dementia cases, it’s hard to diagnose because it can be caused by many different things. These include infections, immune system problems, brain diseases like Alzheimer’s, or rare conditions like Creutzfeldt-Jakob disease.
Because there are so many possible causes, doctors haven’t had a consistent way to define RPD. That makes it harder to study or treat effectively.
To help with this, researchers created a new definition based on a standard tool called the Clinical Dementia Rating (CDR) scale. This scale measures how much someone’s memory, problem-solving, orientation, and personal care are affected.
The researchers came up with a simple “1-in-1 or 2-in-2” rule. That means someone has RPD if they show signs of mild dementia (a CDR score of 1 or more) within one year of when their symptoms started, or moderate to severe dementia (a CDR score of 2 or more) within two years.
To test this idea, the researchers used two large sets of data. One came from Mayo Clinic and Washington University and included 248 people who were being evaluated for RPD. The other came from the National Alzheimer’s Coordinating Center, which included more than 19,000 people from 46 research centers across the U.S.
In the Mayo/Washington University group, about 75% of patients met the new definition. About one-third of them had causes like autoimmune or inflammatory diseases, many of which can be treated.
In the larger national dataset, about 4% met the new RPD criteria. Alzheimer’s disease was the most common cause of RPD in this group. People who met the RPD definition declined three to four times faster than those with more typical, slower-moving dementia.
One big strength of this new definition is that it worked well in both small clinical settings and large research groups. It can also be used based on a patient’s history and symptoms without needing special tests, which makes it helpful even in hospitals or clinics that don’t have access to advanced tools.
This research is important because catching RPD early might help doctors identify cases that can be treated. It also makes research easier, since scientists now have a shared definition to use when studying fast-moving dementia. Having a standard way to identify RPD could help launch more clinical trials to test new treatments.
In summary, this study presents a simple, evidence-based way to define RPD using tools that doctors already know. It could make a big difference in how quickly patients get help, especially those who might have reversible causes of dementia.
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The study is published in Neurology.
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