7 Million Americans Have Mild Cognitive Impairment and Don't Know It

October 26, 2023
Amy Norton HealthDay Reporter

Millions of older Americans may be unaware they have memory and thinking impairments -- mostly because their doctors aren't diagnosing them, new research suggests.

After analyzing Medicare data covering 40 million older Americans, researchers found that only a small percentage of expected cases of mild cognitive impairment (MCI) were actually diagnosed. The upshot was that more than 7 million cases went undetected.

Mild cognitive impairment refers to problems with memory, judgment, language and other mental skills that are not disabling, but go beyond the occasional slips that are expected with age.

MCI may turn up as forgotten appointments, regularly misplacing things, trouble following the plot of a book or movie, or difficulty navigating well-known places.

Some older adults with MCI eventually develop Alzheimer's -- around 10% per year, according to the Alzheimer's Association.

But more often, MCI has other, often reversible causes, said Dr. Saket Saxena, a geriatrician at the Cleveland Clinic who was not involved in the new research.

Those causes run the gamut, Saxena said -- including medication side effects, low thyroid hormone, depression, untreated sleep apnea, uncontrolled health conditions like diabetes, mobility limitations and social isolation.

"It is not a foregone conclusion that you're going to develop dementia," said senior study author Soeren Mattke, director of the Brain Health Observatory at the University of Southern California in Los Angeles.

And the fact that MCI has treatable, or reversible, causes is a big reason for primary care doctors to look for it, Mattke said.

In reality, his team found, that is rarely happening.

Looking at Medicare data from 2017 to 2019, the researchers found that U.S. primary care doctors detected only about 8% of expected cases of mild cognitive impairment among their older patients.

Based on patient demographics, the researchers predicted about 8 million cases of MCI in the study group. The low detection rate meant that about 7.4 million of those cases went undiagnosed.

"We expected it to be bad, but not that bad," Mattke said.

The findings were published Oct. 24 in The Journal of Prevention of Alzheimer's Disease.

To be fair, Mattke said, a lack of formal diagnoses in Medicare records does not necessarily mean that doctors aren't talking to patients about their memory complaints or other symptoms.

And no one is saying that primary care doctors are simply ignoring older patients' cognitive health.

They face a lot of obstacles, said Rebecca Edelmayer, senior director of scientific engagement for the Alzheimer's Association.

In a 2022 survey, the association found that 77% of primary care doctors found MCI difficult to diagnose, and many said that patients are reluctant to pursue a diagnosis. On top of that, primary care doctors have so much to cover with older patients during a short appointment that a cognitive evaluation may not be doable.

"More needs to be done to support primary care doctors, by providing the information, tools and resources to increase early and accurate diagnosis," Edelmayer said.

Saxena agreed that primary care doctors are "not well-prepared to diagnose MCI" -- in part due to a lack of guidance on the issue, but also because there is an assortment of screening tests out there. Saxena called it something of a "Wild West."

He also stressed that screening is only step one: Are primary care doctors then able to go to the "next step" of weeding out the potential causes of a patient's cognitive symptoms?

It's "extremely important," Saxena said, that all of the underlying possibilities be considered.

The study was partially funded by drugmaker Genentech. Mattke has received consulting or speaker fees from various drug companies, including Biogen, maker of the new Alzheimer's drugs Leqembi and Aduhelm.

The recent availability of those medications adds another layer to the MCI detection issue. The drugs, and others under development, are for people in the early stages of Alzheimer's, Edelmayer said. So early detection is "critical," she said.

However, Edelmayer pointed out, determining whether MCI is due to early Alzheimer's takes more than a screening test. There has to be biological evidence of Alzheimer's, too.

To get the new (and very expensive) drugs Leqembi and Aduhelm, people have to undergo testing -- usually a brain scan or spinal tap -- to see whether they have signs of amyloid "plaques" in the brain. The drugs target those abnormal protein deposits, with the aim of slowing Alzheimer's progression.

All three experts agreed, though, that given the many underlying causes of MCI, older adults need to discuss their personal situation with their doctor.

More information

The U.S. National Institute on Aging has more on mild cognitive impairment.

SOURCES: Soeren Mattke, PhD, director, Brain Health Observatory, University of Southern California Dornsife College of Letters, Arts and Sciences, Los Angeles; Rebecca Edelmayer, PhD, senior director, scientific engagement, Alzheimer's Association, Chicago; Saket Saxena, MD, Center for Geriatric Medicine, Cleveland Clinic, Ohio; The Journal of Prevention of Alzheimer's Disease, Oct. 24, 2023, online