Millions Have Mild Cognitive Impairment but Don’t Know It

December 13, 2023

Many older people forget where they placed their car keys or can’t immediately recall an acquaintance’s name. And most write it off as a “senior moment,” an unavoidable accompaniment of growing older.

And in most cases, occasional forgetfulness is nothing to worry about. But for some people, memory lapses can be an early symptom of something more serious: mild cognitive impairment, or MCI, a brain disorder that can progress to full-blown dementia.

Two new studies from researchers at the University of Southern California suggest that MCI is far more common than most people think. The researchers estimate that millions of Americans are living with MCI but don’t know it. In many cases, their primary care physicians are missing the diagnosis.

In one study, published in Alzheimer’s Research & Therapy, researchers analyzed data from 40 million Medicare beneficiaries aged 65 and older. They estimated that about eight million of them would be expected to have MCI, based on their age, gender and medical history. But fewer than 8 percent of them had been given a diagnosis of MCI, meaning an estimated 7.4 million Americans remained undiagnosed. Diagnostic rates were lowest among Black and Hispanic seniors.

“This study is meant to raise awareness of the problem,” said study leader Dr. Soeren Mattke, director of the Brain Health Observatory at USC Dornsife’s Center for Economic and Social Research. “We want to say, ‘Pay attention to early changes in cognition, and tell your doctor about them. Ask for an evaluation.’”

In a second study, published in the Journal of Prevention of Alzheimer’s Disease, Dr. Mattke and his colleagues evaluated medical records among 226,756 primary care physicians who were practicing across the country. Again, they found that only about 8 percent of cases were properly diagnosed. A main reason: 99 percent of primary care doctors missed the diagnosis in at least some of their patients.

“Mild cognitive impairment is vastly underdiagnosed, pointing to an urgent need to improve early detection in primary care,” the authors concluded.

Why do so many primary care doctors miss the diagnosis? Unlike neurology specialists, many primary care doctors do not have the training to properly diagnose MCI — and many don’t have the time to conduct in in-depth memory assessment. In addition, many patients are reluctant to talk about their memory problems. Unfortunately, “there’s really just a tiny fraction of physicians in a position to diagnose MCI who would find these cases early enough for maximum therapeutic potential,” Dr. Mattke said. 

A proper diagnosis of MCI is important for several reasons. In some cases, the condition is reversible. Certain drugs and medications — anti-anxiety drugs and sleeping pills, anticonvulsants, steroids, opioid pain relievers, and certain antidepressants, for example — can cause “brain fog,” personality changes, or other symptoms of MCI. In such cases,a doctor can adjust the dose or substitute an alternative drug, which may readily reverse the memory problems. 

Early diagnosis of MCI may also allow for early, more effective treatment. Some recently approved drugs for Alzheimer’s, such as Leqembi, for example, are designed to slow the progression of the disease. These drugs may be most effective when given early, before damage to the brain becomes extensive, experts believe.  

“For MCI caused by Alzheimer’s disease, the earlier you treat, the better your outcomes,” Dr. Mattke said. “This means even though the disease may be slowly progressing, every day counts.”  

If you are concerned about memory issues, discuss it with your doctor. Not everyone who has MCI will ultimately develop Alzheimer’s disease or other forms of dementia. Your doctor can refer you to a specialist or look for underlying medical conditions or medications that may be causing the memory loss. In many cases, mild cognitive impairment can be reversed. 

By ALZinfo.org, The Alzheimer’s Information Site. Reviewed by Eric Schmidt, Ph.D., Fisher Center for Alzheimer’s Research Foundation at The Rockefeller University.  

Sources: Ying Liu, H. Jun, A. Becker, et al: “Detection Rates of Mild Cognitive Impairment in Primary Care for the United States Medicare Population.” The Journal of the Prevention of Alzheimer’s Disease, Oct. 24, 2023 

Soeren Mattke, Hankyung Jun, Emily Chen, et al: “Expected and diagnosed rates of mild cognitive impairment and dementia in the U.S. Medicare population: observational analysis.” Alzheimer’s Research & Therapy, July 22, 2023


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