Medicine:Mild cognitive impairment

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Short description: Neurocognitive disorder
Not to be confused with minimal brain dysfunction.
Mild cognitive impairment
Other namesIncipient dementia, isolated memory impairment, mild neurocognitive disorder
SpecialtyNeurology
SymptomsCan include memory impairments (amnestic) or cognitive problems like impaired decision making, language, or visuospatial skills (non-amnestic)
Usual onsetTypically appears in adults 65 or older
TypesAmnestic, non-amnestic
Risk factorsAge, family history, cardiovascular disease
Diagnostic methodBased on symptoms assessed by a clinical neuropsychologist through observations, neuroimaging, and blood tests

Mild cognitive impairment (MCI) is a diagnosis that reflects an intermediate stage of cognitive impairment that is often, but not always, a transitional phase from cognitive changes in normal aging to those typically found in dementia,[1] especially dementia due to Alzheimer's disease (Alzheimer's dementia).[2] MCI may include both memory and non-memory neurocognitive impairments.[3] About 50 percent of people diagnosed with MCI have Alzheimer's disease and go on to develop Alzheimer's dementia within five years. MCI can also serve as an early indicator for other types of dementia, although MCI may also remain stable or remit.[4] Many definitions of MCI exist. A common feature of many of these is that MCI involves cognitive impairments that are measurable but that are not significant enough to interfere with instrumental activities of daily living.[1]

The DSM-5 introduces the concept of mild neurocognitive disorder (mNCD), which is designed to be largely equivalent to MCI.[5] The International Classification of Diseases (ICD-11) refers to MCI as "Mild Neurocognitive Disorder (MND)".[6] It is controversial whether MCI should be used as a diagnosis.[7]

The definition of MCI continues to evolve. Academic discussion revolves around whether MCI should be classified or diagnosed algorithmically or clinically, the reliability of clinical judgment, stability of the diagnosis over time, and the utility or predictivity of biomarkers. Differences in the definition and implementation of the MCI construct can explain some discrepancies between research studies.[8]

Classification

MCI can present with a variety of symptoms, but is divided generally into two types.[4]

Amnestic MCI (aMCI) is mild cognitive impairment with memory loss as the predominant symptom; aMCI is frequently seen as a prodromal stage of Alzheimer's disease.[4][3][9] Studies suggest that these individuals tend to progress to probable Alzheimer's disease at a rate of approximately 10% to 15% per year.[needs update][10] It is possible that being diagnosed with cognitive decline may serve as an indicator of MCI.[11]

Nonamnestic MCI (naMCI) is mild cognitive impairment in which impairments in domains other than memory (for example, language, visuospatial, executive) are more prominent.[4][12] It may be further divided as nonamnestic single- or multiple-domain MCI, and these individuals are believed to be more likely to convert to other dementias (for example, dementia with Lewy bodies).[13]

Causes

Mild cognitive impairment (MCI) may be caused due to alteration in the brain triggered during early stages of Alzheimer's disease, to other causes, or to a combination of causes.[14][15] Brain damage, brain injury, delirium and prolonged substance abuse can cause MCI. HIV-associated neurocognitive disorder can cause MCI. Risk factors of both dementia and MCI are the same, and include: aging, genetics, and cardiovascular disease.[16] There is a significant association between mild cognitive impairment (MCI) and hearing impairment, although most cases of MCI are not due to hearing impairment. Hearing loss in individuals with MCI may contribute to further cognitive decline; however, this relationship may also reflect shared neuropathological processes involving cortical regions responsible for auditory function[17].

Diagnosis

The first step in the diagnosis is screening. Montreal Cognitive Assessment (MoCA) is one of the screening tools that may guide a detailed evaluation.[18] The diagnosis of MCI requires clinical judgement,[10] possibly including clinical observation, neuroimaging,[19] blood tests and neuropsychological testing. MCI may be diagnosed differently by different clinicians using different definitions or criteria, but generally including:[20]

  1. Evidence of modest cognitive decline from a previous level of performance in one or more cognitive domains, based on either: concern about cognitive decline from the individual, a knowledgeable informant, or a clinician, or modest impairment in cognitive performance documented by standardized neuropsychological testing.
  2. The cognitive deficits do not interfere with capacity for independence in everyday activities. However, greater effort, compensatory strategies, or accommodation may be required for complex tasks.

Neuropathology

Magnetic resonance imaging can observe deterioration, including progressive loss of gray matter in the brain, from MCI to full-blown Alzheimer dementia.[21] A technique known as PiB PET imaging is used to show the sites and shapes of beta amyloid deposits in living subjects using a 11C tracer that binds selectively to such deposits.[22] Individuals with MCI may have increased oxidative damage in their nuclear and mitochondrial brain DNA.[23]

Treatment

See also: Philosophy:Neurobiological effects of physical exercise

The American Academy of Neurology's (AAN) clinical practice guideline on MCI from January 2018 stated that clinicians should identify modifiable risk factors in individuals with MCI, assess functional impairments, provide treatment for any behavioral or neuropsychiatric symptoms, and monitor the individual's cognitive status over time.[4] It also stated that medications which cause cognitive impairment should be discontinued or avoided if possible.[4] Due to the lack of evidence supporting the efficacy of cholinesterase inhibitors in individuals with MCI, the AAN guideline stated that clinicians who choose to prescribe them for the treatment of MCI must inform patients about the lack of evidence supporting this therapy.[4] The guideline also indicated that clinicians should recommend that individuals with MCI engage in regular physical exercise for cognitive symptomatic benefits;[4] clinicians may also recommend cognitive training, which appears to provide some symptomatic benefit in certain cognitive measures.[4] Current evidence suggests that cognition-based interventions do improve mental performance (i.e. memory, executive function, attention, and speed) in older adults and people with mild cognitive impairment.[24] Especially, immediate and delayed verbal recall resulted in higher performance gains from memory training.

Diet improvements are likely beneficial to MCI. However, there is currently limited evidence to form a strong conclusion to recommend particular carbohydrate supplements in preventing or reducing cognitive decline in older adults with normal cognition or mild cognitive impairment.[25]

According to research conducted in England, people with MCI often do not receive adequate care and support in healthcare settings. This leaves them and their families in a limbo with uncertainty regarding their futures and the fear of possibly developing dementia. The lack of services also fails to point them to effective ways to prevent dementia such as exercise and social contact. Successful dementia prevention services would have to be tailored to people's preferences and backgrounds.[26][27]

As MCI may represent a prodromal state to clinical Alzheimer's dementia, treatments for Alzheimer's disease could potentially be useful.[28] Of these, rivastigmine failed to stop or slow progression to Alzheimer's disease or to improve cognitive function for individuals with mild cognitive impairment;[29] donepezil showed only minor, short-term benefits and was associated with significant side effects.[30]

Outlook

MCI does not usually interfere with daily life.[4]

Prevalence

The prevalence of MCI varies by age.[4] The prevalence of MCI among different age groups is as follows: 6.7% for ages 60–64; 8.4% for ages 65–69, 10.1% for ages 70–74, 14.8% for ages 75–79, and 25.2% for ages 80–84.[4] After a two-year follow-up, the cumulative incidence of dementia among individuals who are over 65 years old and were diagnosed with MCI was found to be 14.9%.[4]

Due to the emphasis shifting to the earlier diagnosis of dementia, more people are assessed who report memory problems. In turn this also leads diagnosing more people who might have MCI which is a risk factor for dementia.[26][27] Globally, approximately 16% of the population over the age of 70 experiences some type of MCI.

History

MCI was initially conceptualized as an intermediate stage between normal aging and Alzheimer's disease.[31] In 2003 international criteria for MCI were developed that broadened the definition to include people with cognitive impairment due to any etiology.[32] Furthermore, the definition of Alzheimer's disease expanded to include earlier, non-dementia, stages. So now, MCI can either be a diagnosis associated with early Alzheimer's disease (i.e., people with MCI that also have Alzheimer's disease) or a diagnosis of cognitive decline due to a cause other than Alzheimer's disease; it is no longer considered to be a stage between normal aging and Alzheimer's disease.[33]

References

  1. ↑ 1.0 1.1 "Mild cognitive impairment: clinical characterization and outcome". Arch. Neurol. 56 (3): 303–8. 1999. doi:10.1001/archneur.56.3.303. PMID 10190820. 
  2. ↑ "Mild cognitive impairment: is it Alzheimer's disease or not?". J. Alzheimers Dis. 7 (3): 241–5. June 2005. doi:10.3233/jad-2005-7307. PMID 16006668. 
  3. ↑ 3.0 3.1 "White matter microstructural abnormalities in amnestic mild cognitive impairment: A meta-analysis of whole-brain and ROI-based studies". Neurosci Biobehav Rev 83: 405–416. December 2017. doi:10.1016/j.neubiorev.2017.10.026. PMID 29092777. 
  4. ↑ 4.00 4.01 4.02 4.03 4.04 4.05 4.06 4.07 4.08 4.09 4.10 4.11 4.12 "Practice guideline update summary: Mild cognitive impairment – Report of the Guideline Development, Dissemination, and Implementation Subcommittee of the American Academy of Neurology". Neurology. Special article 90 (3): 126–135. January 2018. doi:10.1212/WNL.0000000000004826. PMID 29282327. "In patients with MCI, exercise training (6 months) is likely to improve cognitive measures and cognitive training may improve cognitive measures. ... Clinicians should recommend regular exercise (Level B). ... Recommendation: For patients diagnosed with MCI, clinicians should recommend regular exercise (twice/week) as part of an overall approach to management (Level B).". 
  5. ↑ Sachs-Ericsson, Natalie; Blazer, Dan G. (2015-01-02). "The new DSM-5 diagnosis of mild neurocognitive disorder and its relation to research in mild cognitive impairment" (in en). Aging & Mental Health 19 (1): 2–12. doi:10.1080/13607863.2014.920303. ISSN 1360-7863. PMID 24914889. http://www.tandfonline.com/doi/abs/10.1080/13607863.2014.920303. 
  6. ↑ "ICD-11 - Mortality and Morbidity Statistics". https://icd.who.int/browse11/l-m/en#/http%3a%2f%2fid.who.int%2ficd%2fentity%2f195531803. 
  7. ↑ Wang, Kate N.; Page, Amy T.; Etherton-Beer, Christopher D. (June 2021). "Mild cognitive impairment: To diagnose or not to diagnose". Australasian Journal on Ageing 40 (2): 111–115. doi:10.1111/ajag.12913. ISSN 1440-6381. PMID 33604998. https://onlinelibrary.wiley.com/doi/10.1111/ajag.12913. 
  8. ↑ Petersen, R. C.; Caracciolo, B.; Brayne, C.; Gauthier, S.; Jelic, V.; Fratiglioni, L. (March 2014). "Mild cognitive impairment: a concept in evolution" (in en). Journal of Internal Medicine 275 (3): 214–228. doi:10.1111/joim.12190. ISSN 0954-6820. PMID 24605806. 
  9. ↑ "Mild Cognitive Impairment". Continuum (Minneap Minn) 22 (2 Dementia): 404–18. April 2016. doi:10.1212/CON.0000000000000313. PMID 27042901. 
  10. ↑ 10.0 10.1 "Mild cognitive impairment can be distinguished from Alzheimer disease and normal aging for clinical trials". Arch. Neurol. 61 (1): 59–66. 2004. doi:10.1001/archneur.61.1.59. PMID 14732621. 
  11. ↑ "Investigations of Memory Monitoring in Individuals With Subjective Cognitive Decline and Amnestic Mild Cognitive Impairment". Cogn Behav Neurol 33 (3): 201–207. September 2020. doi:10.1097/WNN.0000000000000242. PMID 32889952. 
  12. ↑ "Mild cognitive impairment as a diagnostic entity". Journal of Internal Medicine 256 (3): 183–194. September 2004. doi:10.1111/j.1365-2796.2004.01388.x. ISSN 0954-6820. PMID 15324362. 
  13. ↑ "Neuropsychological prediction of conversion to Alzheimer disease in patients with mild cognitive impairment". Arch. Gen. Psychiatry 63 (8): 916–24. 2006. doi:10.1001/archpsyc.63.8.916. PMID 16894068. 
  14. ↑ "Mild cognitive impairment (MCI)". Mayo Clinic. https://www.mayoclinic.org/diseases-conditions/mild-cognitive-impairment/symptoms-causes/syc-20354578. 
  15. ↑ Petersen, R. C.; Caracciolo, B.; Brayne, C.; Gauthier, S.; Jelic, V.; Fratiglioni, L. (March 2014). "Mild cognitive impairment: a concept in evolution" (in en). Journal of Internal Medicine 275 (3): 214–228. doi:10.1111/joim.12190. ISSN 0954-6820. PMID 24605806. 
  16. ↑ "Mild Cognitive Impairment". Alzheimer's Association. http://www.alz.org/dementia/mild-cognitive-impairment-mci.asp. 
  17. ↑ Lopes, Leonardo da Costa; Magaldi, Regina Miksian; Gândara, Mara Edwirges Rocha; Reis, Ana Carolina de Barros; Jacob-Filho, Wilson (2007). "Prevalence of hearing impairment in patients with mild cognitive impairment". Dementia & Neuropsychologia 1 (3): 253–259. doi:10.1590/S1980-57642008DN10300006. ISSN 1980-5764. http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1980-57642007000300253&lng=en&tlng=en. 
  18. ↑ Nasreddine, Ziad S.; Phillips, Natalie A.; Bédirian, Valérie; Charbonneau, Simon; Whitehead, Victor; Collin, Isabelle; Cummings, Jeffrey L.; Chertkow, Howard (2005-04). "The Montreal Cognitive Assessment, MoCA: A Brief Screening Tool For Mild Cognitive Impairment" (in en). Journal of the American Geriatrics Society 53 (4): 695–699. doi:10.1111/j.1532-5415.2005.53221.x. ISSN 0002-8614. https://agsjournals.onlinelibrary.wiley.com/doi/10.1111/j.1532-5415.2005.53221.x. 
  19. ↑ "18F-FDG PET for the early diagnosis of Alzheimer's disease dementia and other dementias in people with mild cognitive impairment (MCI)". Cochrane Database Syst Rev 1 (1). January 2015. doi:10.1002/14651858.CD010632.pub2. PMID 25629415. 
  20. ↑ "Mild cognitive impairment represents early-stage Alzheimer disease". Arch. Neurol. 58 (3): 397–405. March 2001. doi:10.1001/archneur.58.3.397. PMID 11255443. 
  21. ↑ "MRI patterns of atrophy associated with progression to AD in amnestic mild cognitive impairment". Neurology 70 (7): 512–20. 2008. doi:10.1212/01.wnl.0000280575.77437.a2. PMID 17898323. 
  22. ↑ "11C PiB and structural MRI provide complementary information in imaging of Alzheimer's disease and amnestic mild cognitive impairment". Brain 131 (Pt 3): 665–80. 2008. doi:10.1093/brain/awm336. PMID 18263627. 
  23. ↑ "Increased oxidative damage in nuclear and mitochondrial DNA in mild cognitive impairment". J. Neurochem. 96 (3): 825–32. February 2006. doi:10.1111/j.1471-4159.2005.03615.x. PMID 16405502. 
  24. ↑ "Cognition-based interventions for healthy older people and people with mild cognitive impairment". The Cochrane Database of Systematic Reviews (1). January 2011. doi:10.1002/14651858.cd006220.pub2. PMID 21249675. 
  25. ↑ "Carbohydrates for improving the cognitive performance of independent-living older adults with normal cognition or mild cognitive impairment". The Cochrane Database of Systematic Reviews 2011 (4). April 2011. doi:10.1002/14651858.cd007220.pub2. PMID 21491398. 
  26. ↑ 26.0 26.1 Saul, Helen (2020-10-23) (in en-GB). People with mild memory problems are left in limbo between health and dementia, and need help to make lifestyle changes. National Institute for Health and Care Research. doi:10.3310/alert_42131. https://evidence.nihr.ac.uk/alert/people-with-mild-memory-problems-are-left-in-limbo-between-health-and-dementia-and-need-help-to-make-lifestyle-changes/. Retrieved 2022-12-05. 
  27. ↑ 27.0 27.1 Poppe, Michaela; Mansour, Hassan; Rapaport, Penny; Palomo, Marina; Burton, Alexandra; Morgan-Trimmer, Sarah; Carter, Christine; Roche, Moïse et al. (1 July 2020). "" Falling through the cracks "; Stakeholders' views around the concept and diagnosis of mild cognitive impairment and their understanding of dementia prevention" (in en). International Journal of Geriatric Psychiatry 35 (11): 1349–1357. doi:10.1002/gps.5373. ISSN 0885-6230. PMID 32608171. 
  28. ↑ Feng, Lei; Cheah, Irwin Kee-Mun; Ng, Maisie Mei-Xi; Li, Jialiang; Chan, Sue Mei; Lim, Su Lin; Mahendran, Rathi; Kua, Ee-Heok et al. (2019-03-12). Yu, Jin-Tai. ed. "The Association between Mushroom Consumption and Mild Cognitive Impairment: A Community-Based Cross-Sectional Study in Singapore". Journal of Alzheimer's Disease 68 (1): 197–203. doi:10.3233/JAD-180959. PMID 30775990. https://www.medra.org/servlet/aliasResolver?alias=iospress&doi=10.3233/JAD-180959. 
  29. ↑ "Effect of rivastigmine on delay to diagnosis of Alzheimer's disease from mild cognitive impairment: the InDDEx study". Lancet Neurol 6 (6): 501–12. 2007. doi:10.1016/S1474-4422(07)70109-6. PMID 17509485. 
  30. ↑ "Donepezil for dementia due to Alzheimer's disease". Cochrane Database Syst Rev 2018 (6). June 2018. doi:10.1002/14651858.CD001190.pub3. PMID 29923184. 
  31. ↑ Petersen, R. C. (September 2004). "Mild cognitive impairment as a diagnostic entity" (in en). Journal of Internal Medicine 256 (3): 183–194. doi:10.1111/j.1365-2796.2004.01388.x. ISSN 0954-6820. PMID 15324362. https://onlinelibrary.wiley.com/doi/10.1111/j.1365-2796.2004.01388.x. 
  32. ↑ Petersen, R. C.; Caracciolo, B.; Brayne, C.; Gauthier, S.; Jelic, V.; Fratiglioni, L. (March 2014). "Mild cognitive impairment: a concept in evolution" (in en). Journal of Internal Medicine 275 (3): 214–228. doi:10.1111/joim.12190. ISSN 0954-6820. PMID 24605806. 
  33. ↑ "Alzheimer's Disease Facts and Figures 2024". 2024. https://www.alz.org/media/Documents/alzheimers-facts-and-figures.pdf. 
Classification



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