Mild cognitive impairment is widely underdiagnosed among older Americans

Mild cognitive impairment - an early stage of dementia - is substantially underdiagnosed among people aged 65 and over. That is the central conclusion from two recent studies conducted by our team.

For the first study, we examined Medicare data covering roughly 40 million beneficiaries aged 65 and older between 2015 and 2019. We estimated the prevalence of mild cognitive impairment in this group and determined how many people had received a diagnosis.

The results were concerning: just 8% of the cases of mild cognitive impairment predicted by our statistical model had been diagnosed. Applied to the wider population aged 65 and over, this suggests that around 7.4 million cases nationwide have not been identified.

In our second study, we assessed data on 226,756 primary care clinicians. More than 99% were found to underdiagnose mild cognitive impairment among this population.

Why mild cognitive impairment matters

In around half of cases, mild cognitive impairment is an early sign of Alzheimer's disease, and it develops into dementia at an annual rate of 10% to 15%. Symptoms may include an impaired ability to recall recent events and appointments, make well-founded decisions and manage complex tasks.

When it goes undetected, patients may miss the chance to receive treatment that could slow the disease's progression.

There are instances in which mild cognitive impairment results from readily treatable causes, including medication side effects, thyroid dysfunction or vitamin B12 deficiency.

Mild cognitive impairment shares risk factors with cardiovascular disease, including high blood pressure and cholesterol. Managing these risks with medication, alongside diet and exercise, can lower the likelihood of progression.

In 2023, the Food and Drug Administration approved lecanemab, the first disease-modifying treatment for Alzheimer's disease, which is the most common cause of mild cognitive impairment. Unlike earlier medicines that may temporarily ease symptoms such as memory loss and agitation, this newer treatment targets the disease's underlying cause.

Lecanemab is a monoclonal antibody that reduces amyloid plaques in the brain - toxic protein clumps thought to contribute to disease progression. In a large clinical trial, lecanemab reduced the progression of early-stage Alzheimer's disease. Donanemab, a similar drug, also proved successful in a clinical trial and was expected to receive approval at some point in 2024.

These medicines must, however, be given during the early stages of Alzheimer's disease - ideally while a patient has only mild cognitive impairment - because there is no evidence that they work in advanced stages.

What remains unknown

Numerous factors contribute to delayed detection. Yet researchers do not fully understand the relative significance of each factor or how the high level of underdiagnosis can be reduced.

Although the symptoms are distinct, they can be subtle, and their gradual onset means they may be missed or mistaken for normal ageing. A neurologist in China told our research team that diagnosis rates rise after the New Year's holiday, when children who have not seen their parents for a year spot changes that can be more difficult to notice through daily interactions.

Doctors also often dismiss memory worries as part of normal ageing and question whether much can be done. Cognitive tests that distinguish mild cognitive impairment from pathological decline are available, but they take around 15 minutes. That time can be difficult to find during a short doctor's appointment and may mean arranging a follow-up visit.

What's next

People - especially those in their 60s and older - together with their families and friends, should watch for cognitive decline, raise concerns during doctor's appointments and request a formal assessment.

The annual Medicare "wellness" visit provides an opportunity to discuss these concerns, although only about half of beneficiaries use it.

Just as doctors ask about unexplained weight loss and treat such concerns seriously, we believe that questions exploring a patient's cognitive state should become routine.

The Research Brief is a short take on interesting academic work.

Soeren Mattke, Director of the USC Dornsife Brain Health Observatory, University of Southern California and Ying Liu, Research Scientist, Center for Economic and Social Research, USC Dornsife College of Letters, Arts and Sciences

This article is republished from The Conversation under a Creative Commons licence. Read the original article.