Are Doctors Missing Millions of Cases of Mild Cognitive Impairment?

Are doctors able to spot the signs of cognitive impairment in their older patients? According to two new research studies, doctors miss the majority of cases. In fact, these studies suggest that more than seven million people, or 92 percent of people with  mild cognitive impairment (MCI) in the population, haven’t gotten a diagnosis. Overall, researchers found that 99.9 percent of doctors tend to under-diagnose the condition.   

MCI is a brain health condition where people start to experience more problems remembering things like important dates or appointments, have trouble remembering a certain word they want to say, and develop more problems with thinking and planning than other individuals their age. Diagnosis is important because many cases of MCI have underlying causes — from thyroid hormone dysfunction, to depression, to vitamin B deficiency — that can be treated. And with treatment, experts say, these types cases can be reversed. 

In some cases, MCI can be a precursor to Alzheimer’s disease and other dementias. Diagnosing it accurately and early could mean a patient has more time to plan for the future with their loved ones. It could also mean an opportunity to institute lifestyle changes that may help them stay healthy for longer, make them eligible for early-stage, disease-modifying Alzheimer’s drugs, and create an opportunity to participate in clinical trials.

But are doctors really missing 92 percent of MCI cases? Some experts found the studies to leave glaring questions, and the way they were covered in the media, some doctors told Being Patient, was unnecessarily alarming.

Digging into the studies

These scientific articles were covered in an alarming way in the media, according to Dr. Madhav Thambisetty, neurologist and senior clinical investigator at the National Institute on Aging, and other experts Being Patient spoke with. One of the most concerning headlines read: “Physicians are dramatically underdiagnosing early cognitive decline, a precursor to Alzheimer’s.” 

Ten to 20 percent of cases of MCI do develop into dementia within a year if their underlying condition goes untreated. However, Thambisetty emphasized, not all MCI cases are all linked to Alzheimer’s: Only a percentage are driven by Alzheimer’s pathology. He worried that the coverage of these studies made that unclear. 

“Several studies have shown that patients diagnosed with MCI can revert back to normal cognition over time,” Thambisetty said. And following news headlines like this, people may panic they have Alzheimer’s disease, when in reality the cause of their cognitive symptoms is a different driver of MCI — a treatable one — such as vitamin B12 deficiency, or thryroid dysfunction.

“A diagnosis of MCI, especially if linked to Alzheimer’s, may be devastating to a patient,” Dr. Adriane Fugh-Berman, a clinician and professor at Georgetown University who researches marketing in the pharmaceutical industry, told Being Patient. “What purpose is served in telling people they have something that is an unclear diagnosis with unclear ramifications — unless the purpose is to put them on a drug?”

On that note, the studies’ news coverage did discuss new treatments for the early stages of Alzheimer’s disease, i.e. the recently FDA-approved monoclonal antibody treatment Leqembi. And the study itself was partially funded by a pharmaceutical company developing new antibody-based treatments for Alzheimer’s.

University of South Carolina Brain Health Observatory director Soeren Mattke — an author on both studies who was heavily quoted across many news articles — has also served as a board member or consultant for several pharmaceutical companies developing these antibodies and biomarker tests for the disease.

While this was included in the disclosure section of the scientific articles, it was not mentioned by news sites, Thambisetty pointed out. And many articles didn’t interview other researchers or experts in their coverage. 

“While these Conflict of Interest disclosures are included in the journal article, they are seldom reported in the media stories that patients and their loved ones read,” Thambisetty said. In addition to explaining these studies in non-technical terms, he also believes it is important “that patients and their caregivers are fully aware of potential conflicts of interests when scientists are quoted in the media.”   

Study media coverage frequently made the leap from the fact that many people may have undiagnosed MCI to the fact that new disease-modifying treatments for Alzheimer’s disease are coming to market, and while third-party experts maintain this link between the two topics can be confusing, and unnecessarily alarming, for patients, there remains the studies’ interesting, face-value takeaway: that MCI may be dramatically underdiagnosed.

While these aren’t all going to be undiagnosed cases of pre-Alzheimer’s, Thambisetty noted, MCI is a cognitive condition that needs a closer look, and often, treatment can make a big and helpful difference.

Let’s take a closer look at what the studies actually showed.

Catching the undiagnosed cases of MCI

In the first of these two 2023 studies, researchers from the University of Southern California set out to see how many older individuals in the population likely had MCI and whether they were being diagnosed with MCI appropriately. 

To get an estimate of MCI in the general population, the researchers looked at data from the Health and Retirement Study that collected cognitive assessments from 20,000 older Americans every two years between 2000 and 2016. 

Participants from the study were divided into one of three groups based on their cognitive abilities: 

• cognitively healthy, 
• living with cognitive impairment but no dementia, and 
• living with dementia. 

The researchers caculated the proportion of people with cognitive impairment against total study population to get a baseline rate of MCI in the population. 

Then, the researchers dove into Medicare administrative data, which would record medical information and diagnoses for all Medicare users, looking to see how often a code for “mild cognitive impairment of uncertain or unknown etiology” popped up. 

While they expected 8 million Americans to have MCI based on the Health and Retirement Study, only 600,000 were diagnosed, according to Medicare data. 

Mattke told Being Patient that this study “showed that only 8 percent of expected MCI cases have been diagnosed.”

However,Thambisetty, noticed a bit of a problem: When asked for his take on the research, he said the researchers were, to put it simply, drawing conclusions about apples by looking at oranges. 

The researchers compared a Medicare code that indicated MCI of an uncertain or unknown cause — meaning it excluded people with depression or other conditions that cause MCI. Meanwhile the Health and Retirement Study, which lumped in cognitive impairment caused by many different conditions together. For example, some of the people who were marked as cognitively impaired in the Health and Retirement Study had known underlying conditions like depression, bipolar disorder, or drug use.

In other words, the Health and Retirement Study cast a much wider net as to who was classified as having actual, diagnosable cognitive impairment. 

Doctors aren’t using the Medicare codes that denote MCI as frequently as data might indicate they should

The second study looked at how often doctors were using Medicare diagnostic codes which indicate they’ve diagnosed someone with MCI of an uncertain or unknown cause.  Researchers wanted to see whether certain practices or clinics weren’t using this code often enough, considering how often they’d expect to see it based on the rates of MCI from the Health and Retirement Study. 

For example, if clinics were underdiagnosing MCI, they would input this code less often into the system compared to the baseline rate of MCI in the population. The authors found that 99.9 percent of doctors were underdiagnosing patients.

Mattke said that there may be many reasons for doctors to underdiagnose MCI. “Patients may not realize that they have [MCI] and/or be reluctant to bring it up,” he told Being Patient, noting that some patients, if they were to receive a medical diagnosis of mild cognitive impairment, fear there will be consequences for their independence, their employment and other concerns.

Doctors, according to Mattke, might also discount the symptoms as normal aging or fail to consider the diagnosis to be consequential despite that some cases of MCI could be resolved with proper treatment. They might also be too pressed for time to investigate further. 

Thambisetty said that the researchers didn’t establish a good rationale for why this Medicare diagnostic code was being under-used. He points out that this study uses the same flawed approach of establishing a baseline of MCI rates from the Health and Retirement study. The researchers also didn’t look into why clinics weren’t using the code, Thambisetty said, so there are still questions to answer as to why this gap exists. 

What should you do if you think you have MCI?

No matter what you read in the news, and regardless of what these studies can tell us or not tell us about MCI diagnosis: If you’re worried about memory or other cognitive problems, ask a brain health expert about the difference between normal aging and something more serious (or read up on it in a reliable, science-backed health publication), and if you feel like something may be going on, “don’t let doctors dismiss your concerns,” as neurologist Dr. Marwan Sabbagh said in a Being Patient Live Talk on dementia diagnosis. If you feel they’re not taking your concerns seriously enough, ask for a referral to a specialist. There are many underlying reasons you might be feeling off, and there may well be steps you can take to treat and even reverse these issues.

When patients come to Dr. Bill Burke, M.D., director of the Stead Family Memory Center at the Banner Alzheimer’s Institute with these concerns, he says he’ll first look at factors that could drive MCI, like depression and anxiety. thyroid function, and vitamin B 12 levels, as well as general blood chemistry and blood count. “Then I want to do a neurologic exam to see if there’s any signs of something affecting the brain that we can see a signal of,” Burke told Being Patient in a past interview. “Has there been a stroke? Might there be a tumor in the brain? So you can do a lot, just strictly with a pretty straightforward physical exam, some really basic laboratory testing, some really basic paper-and-pencil testing, and sort out whether there’s something serious going on or not.”

In Thambisetty’s practice, he too takes a patient’s history, performs a neurological exam, and conducts a variety of other tests to see what might be causing the MCI, and whether it is treatable. He also suggests patients should seek cognitive testing every six to 12 months following an MCI diagnosis to track their symptoms.