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Millions of Americans and their doctors are in the dark when it comes to early cognitive decline, according to new research from the University of Southern California. A study out this week suggests that most general physicians vastly under-diagnose mild cognitive impairment among their patients, following another recent study from the same authors which found that millions of Medicare patients with the condition slip through the cracks. The researchers say this diagnostic gap is worrying, given the importance of recognizing and treating mild cognitive impairment before it becomes more serious.
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It’s well established that mild cognitive impairment is under-diagnosed in older people, but the researchers say theirs is some of the first work to quantify the current size of the problem.
“It’s a very different conversation to have when we can point to these numbers,” senior study author Soeren Mattke, director of the Brain Health Observatory at USC Dornsife’s Center for Economic and Social Research, told Gizmodo over the phone.
In the latest study, published Tuesday in The Journal of Prevention of Alzheimer’s Disease, the team looked at Medicare administrative data collected from over 200,000 primary care clinicians and 50,000 practices between 2017 to 2019. They found that doctors and practices failed to diagnose about 92% of expected mild cognitive impairment cases on average; they also estimated that only 0.1% of physicians accurately diagnosed it as often as they should, based on expected rates.
In the previous paper, published this July in the journal Alzheimer’s Research & Therapy, the authors examined the medical records of over 40 million Americans over 65 enrolled in Medicare and Medicare Advantage plans between 2015 to 2019.
Based on other research, about 8 million of these Americans should have mild cognitive impairment, defined as noticeable memory loss or cognitive decline that doesn’t yet impede a person’s everyday activities. But although the rate did slightly improve over time, only a small portion of Medicare patients actually received this diagnosis during the study period, amounting to about 8% of expected cases.
In other words, at least 7.4 million Americans over 65 have no idea they’re living with mild cognitive impairment, with the authors further estimating that as many as 10 million Americans are undiagnosed if you include those over age 50.
Many, if not most, people will experience some degree of cognitive decline as they age, and not every case will lead to significant issues. But oftentimes, mild cognitive impairment is the first stage of a more serious neurodegenerative disorder, particularly Alzheimer’s disease, the most common form of dementia. About 10% to 15% of these cases in people over 65 will progress to full-blown dementia annually, according to the Alzheimer’s Association, while one-third of people with mild cognitive impairment due to Alzheimer’s will develop dementia within five years.
“With MCI, there are actually a chunk of cases that have their easy fixes—some might be caused by medication side effects or vitamin deficiencies, and all kinds of things we can address if cases are detected,” Mattke said. “And we are starting to see disease-modifying treatments that might be able to change the trajectory of degenerative conditions like Alzheimer’s.”
These treatments, such as the now fully approved anti-amyloid drug Leqembi, seem to provide modest clinical benefits at best for now. But many experts believe that these drugs can be improved and combined to someday substantially delay or stop the progression of Alzheimer’s and other dementias. Identifying cases of mild cognitive impairment as early as possible will be necessary to make the most of these treatments.
There are readily available tests for cognitive decline, Mattke notes, though they take time (10 or more minutes) to conduct. Many doctors might not feel compelled to screen for it in their older patients, or may be too busy, and patients might not think to ask for such screening until they’re much further along in their impairment. So Mattke hopes his team’s research can start to make both groups more aware and willing to get ahead of this growing health issue.
“The real important takeaway is that this diagnosis is a race against time,” Mattke said.
