What is Mild Cognitive Impairment?

An Overview

Mild cognitive impairment (MCI) is a condition defined by problems with memory, speech, or decision-making that do not rise to the level of significant interference with every day activities (as compared to Alzheimer’s disease, for example). MCI is formally described as the intermediate stage between the expected cognition decline of aging and the more-serious drop of dementia, according to the Mayo Clinic.1 Approximately 10% to 20% of people older than 65 are diagnosed with it.1,2 Thus, the challenge affects 5.4 to 10.8 million people in the United States.3

According to the Alzheimer’s Association, there are two subtypes of MCI—amnestic (the most common subtype and primarily affecting the memory) and nonamnestic (affecting thinking skills other than memory).4

Symptoms

The most common symptoms in amnestic MCI are memory complaint and forgetting important information such as appointments, conversations, or recent events.4,5

People with nonamnestic MCI show deficits in areas other than memory, including difficulty organizing and planning,6 getting lost in a familiar environment, poor judgment, and skewed depth perception.1

Same Symptoms, Different Diagnosis

There are a number of medications and conditions with symptoms that can mimic MCI, showing there can be other causes beyond the processes of Alzheimer’s. Accordingly, it is important to have a thorough assessment to rule out treatable diseases and determine if a reversible cause exists, including:7

• Infections (e.g., delirium from neurosyphilis, pneumonia, and urinary tract infections)
• Non-Alzheimer’s neurodegenerative diseases (e.g., Parkinson’s disease, Lyme disease)
• Psychiatric illnesses (e.g., bipolar disorder, schizophrenia, major depression)
• Physical phenomena (e.g., strokes, subdural hematoma, cancer)
• Thyroid disease
• Vitamin B12 deficiency
• Medication side effects (e.g., anticholinergics, benzodiazepines, opioid analgesics, and “chemo fog” from cancer chemotherapy
• Sleep apnea

Diagnostic Tests

Cognitive Tests

There are at least six cognitive tests to help diagnose MCI. The two most widely used are the Montreal Cognitive Assessment (MoCA) and neuropsychological testing. The former uses such techniques as word memorization, animal identification, and copying a simple drawing. It requires only 10 to 15 minutes and can be administered in a doctor’s office.8 Neuropsychological testing is often administered by psychologists and requires about two hours to complete.4 Other tests include the Quick Mild Cognitive Impairment (QMCI), the Mini-Mental State Examination (MMSE) score, the Mini-Cog, and the Clinical Dementia Rating (CDR) Score.

Cognitive function is assessed in four cognitive categories, known as cognitive domains.9

These include:

• Executive functioning (e.g., reasoning, problem-solving, and planning)
• Language (e.g., comprehension, fluency, and semantic paraphasia [when an entire word is substituted for another word, such as saying “orange” instead of “apple” to refer to describe an apple])
• Visuospatial skills (movement, depth and distance perception, and spatial navigation – abilities needed for driving, for example)
• Attentional control (e.g., an individual’s ability to concentrate)

Brain Imaging

This is said to be of little help in making an MCI diagnosis. A specialized PET scan for amyloid deposits or slow glucose metabolism may possibly be of diagnostic value, but these procedures are not commonly available and are expensive. Brain imaging could be performed, however, to rule out other causes of cognitive impairment like occult stroke, subdural hematoma, or brain tumor.8,10

Blood Tests

Recently, a blood test had been reported to be promising.11 If these initial results can be confirmed, the test’s optimal role in detecting and classifying MCI must be established.

Clinical Progression

An estimated 60% to 65% of people with amnestic MCI will progress to dementia,12 while 10% to 15% of these patients progress to Alzheimer’s disease.1 According to the National Institute on Aging, this progression could take one to seven years.7 MCI does not, however, always lead to dementia or Alzheimer’s since many people remain stable or even improve over time. Studies have shown that the rate of reversion from MCI to normal or near normal has been reported to range anywhere from 17% to 32%.10

People with nonamestic MCI are thought to be more likely to progress to other neurodegenerative diseases (e.g., Lewy body dementia).13

Prevention

Unfortunately, there are currently no FDA-approved medications to treat MCI. Researchers are increasingly focusing on prevention as a way to slow the development of cognitive decline.13 This includes lifestyle changes (e.g., controlling high blood pressure and cholesterol), treating for depression, increasing socially stimulating activities, and increasing physical activity)1 and performing cognitive training (e.g., crosswords, playing chess, and, somewhat controversially, online games) to enhance problem solving and memory.13 Researchers are also investigating several diets that could boost cognition (including the Ketogenic diet and the Mediterranean diet).

References

1. Mild cognitive impairment (MCI). The Mayo Clinic website. https://www.mayoclinic.org/diseases-conditions/mild-cognitive-impairment/symptoms-causes/syc-20354578.

2. Chehrehnegar N, et al. Early detection of cognitive disturbances in mild cognitive impairment: a systematic review of observational studies. Psychogeriatrics. 2020;20(2):212-228. doi: 10.1111/psyg.12484.

3. Older population and Aging. The United States Census Bureau website. https://www.census.gov/topics/population/older-aging.

4. About mild cognitive impairment. The Alzheimer’s Association website. https://www.alz.org/alzheimers-dementia/what-is-dementia/related_conditions/mild-cognitive-impairment.

5.  Alzheimer Society of Canada. Mild cognitive impairment. https://alzheimer.ca/sites/default/files/files/national/other-dementias/other-dementias_mild-cognitive-impairment.pdf.

6. Executive function. The Psychology Today website. www.psychologytoday.com/us/basics/executive-function.

7. What is Mild Cognitive Impairment? The National Institute on Aging website. https:www.nia.nih.gov/health/what-mild-cognitive-impairment.

8. Cognitive testing. MedlinePlus website. https://medlineplus.gov/lab-tests/cognitive-testing.

9. Petersen RC, et al. Practice guideline update summary: mild cognitive impairment. Neurology. 2018;90:126-135. doi: 10.1212/WNL.0000000000004826.

10. Rosenberg PB, Lyketsos C. Mild cognitive impairment: searching for the prodome of Alzheimer’s disease. World Psychiatr. 2008;7(2):72-78. doi: 10.1002/j.2051-5545.2008.tb00159.x.

11. Palmqvist S, et al. Discriminative accuracy of plasma phosphor-tau 217 for Alzheimer disease vs other neurodegenerative disorders [published online ahead of print July 28, 2020]. JAMA. doi: 10.1001/jama.2020.12134.

12. Busse A, Angermeyer MC, Riedel-Heller SG. Progression of mild cognitive impairment to dementia. A challenge to current thinking. Br J Psychiatr. 2006;189:399-404. https://www.healthline.com/health/mild-cognitive-impairment. June 6, 2016. doi: 10.1192/bjp.bp.105.014779.

13. Spotting the signs of mild cognitive impairment. The American Psychology Association website. https://www.apa.org/monitor/2019/10/ce-corner-impairment. 2019.