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Mild cognitive impairment

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Not to be confused with minimal brain dysfunction.
Mild cognitive impairment
Other namesIncipient dementia, isolated memory impairment
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

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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

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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]

Diagnosis

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The diagnosis of MCI requires clinical judgement,[10] possibly including clinical observation, neuroimaging,[17] blood tests and neuropsychological testing. MCI may be diagnosed differently by different clinicians using different definitions or criteria, but generally including:[18]

  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

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Magnetic resonance imaging can observe deterioration, including progressive loss of gray matter in the brain, from MCI to full-blown Alzheimer dementia.[19] 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.[20] Individuals with MCI may have increased oxidative damage in their nuclear and mitochondrial brain DNA.[21]

Treatment

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See also: 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.[22] 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.[23]

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.[24][25]

As MCI may represent a prodromal state to clinical Alzheimer's dementia, treatments for Alzheimer's disease could potentially be useful.[26] Of these, rivastigmine failed to stop or slow progression to Alzheimer's disease or to improve cognitive function for individuals with mild cognitive impairment;[27] donepezil showed only minor, short-term benefits and was associated with significant side effects.[28]

Outlook

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

Prevalence

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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.[24][25] Globally, approximately 16% of the population over the age of 70 experiences some type of MCI.[medical citation needed]

History

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MCI was initially conceptualized as an intermediate stage between normal aging and Alzheimer's disease.[29] In 2003 international criteria for MCI were developed that broadened the definition to include people with cognitive impairment due to any etiology.[30] 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.[31]

See also

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References

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  1. ^ a b Petersen RC, Smith GE, Waring SC, Ivnik RJ, Tangalos EG, Kokmen E (1999). "Mild cognitive impairment: clinical characterization and outcome". Arch. Neurol. 56 (3): 303–8. doi:10.1001/archneur.56.3.303. PMID 10190820. S2CID 3717948.
  2. ^ Petersen RC, Bennett D (June 2005). "Mild cognitive impairment: is it Alzheimer's disease or not?". J. Alzheimers Dis. 7 (3): 241–5. doi:10.3233/jad-2005-7307. PMID 16006668.
  3. ^ a b Yu J, Lam CL, Lee TM (December 2017). "White matter microstructural abnormalities in amnestic mild cognitive impairment: A meta-analysis of whole-brain and ROI-based studies". Neurosci Biobehav Rev (Meta-analysis and review). 83: 405–416. doi:10.1016/j.neubiorev.2017.10.026. PMID 29092777.
  4. ^ a b c d e f g h i j k l m Petersen RC, Lopez O, Armstrong MJ, et al. (January 2018). "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. doi:10.1212/WNL.0000000000004826. PMC 5772157. 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". Aging & Mental Health. 19 (1): 2–12. doi:10.1080/13607863.2014.920303. ISSN 1360-7863.
  6. ^ "ICD-11 - Mortality and Morbidity Statistics". icd.who.int.
  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. S2CID 231964648.
  8. ^ Petersen, R. C.; Caracciolo, B.; Brayne, C.; Gauthier, S.; Jelic, V.; Fratiglioni, L. (March 2014). "Mild cognitive impairment: a concept in evolution". Journal of Internal Medicine. 275 (3): 214–228. doi:10.1111/joim.12190. ISSN 0954-6820. PMC 3967548.
  9. ^ Petersen RC (April 2016). "Mild Cognitive Impairment". Continuum (Minneap Minn) (Review). 22 (2 Dementia): 404–18. doi:10.1212/CON.0000000000000313. PMC 5390929. PMID 27042901.
  10. ^ a b Grundman M, Petersen RC, Ferris SH, et al. (2004). "Mild cognitive impairment can be distinguished from Alzheimer disease and normal aging for clinical trials". Arch. Neurol. 61 (1): 59–66. doi:10.1001/archneur.61.1.59. PMID 14732621. S2CID 14831757.
  11. ^ Yu H, Wang K, Zhong P, Cheng HD, Lv XY, Yuan LL (September 2020). "Investigations of Memory Monitoring in Individuals With Subjective Cognitive Decline and Amnestic Mild Cognitive Impairment". Cogn Behav Neurol. 33 (3): 201–207. doi:10.1097/WNN.0000000000000242. PMID 32889952. S2CID 221511593.
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  13. ^ Tabert MH, Manly JJ, Liu X, et al. (2006). "Neuropsychological prediction of conversion to Alzheimer disease in patients with mild cognitive impairment". Arch. Gen. Psychiatry. 63 (8): 916–24. doi:10.1001/archpsyc.63.8.916. PMID 16894068.
  14. ^ "Mild cognitive impairment (MCI)". Mayo Clinic. Retrieved 30 Sep 2020.
  15. ^ Petersen, R. C.; Caracciolo, B.; Brayne, C.; Gauthier, S.; Jelic, V.; Fratiglioni, L. (March 2014). "Mild cognitive impairment: a concept in evolution". Journal of Internal Medicine. 275 (3): 214–228. doi:10.1111/joim.12190. ISSN 0954-6820. PMC 3967548. PMID 24605806.
  16. ^ "Mild Cognitive Impairment". Alzheimer's Association. Retrieved July 9, 2017.
  17. ^ Smailagic N, Vacante M, Hyde C, Martin S, Ukoumunne O, Sachpekidis C (January 2015). "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): CD010632. doi:10.1002/14651858.CD010632.pub2. PMC 7081123. PMID 25629415.
  18. ^ Morris JC, Storandt M, Miller JP, McKeel DW, Price JL, Rubin EH, Berg L (March 2001). "Mild cognitive impairment represents early-stage Alzheimer disease". Arch. Neurol. 58 (3): 397–405. doi:10.1001/archneur.58.3.397. PMID 11255443.
  19. ^ Whitwell JL, Shiung MM, Przybelski SA, et al. (2008). "MRI patterns of atrophy associated with progression to AD in amnestic mild cognitive impairment". Neurology. 70 (7): 512–20. doi:10.1212/01.wnl.0000280575.77437.a2. PMC 2734138. PMID 17898323.
  20. ^ Jack CR, Lowe VJ, Senjem ML, et al. (2008). "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. doi:10.1093/brain/awm336. PMC 2730157. PMID 18263627.
  21. ^ Wang J, Markesbery WR, Lovell MA (February 2006). "Increased oxidative damage in nuclear and mitochondrial DNA in mild cognitive impairment". J. Neurochem. 96 (3): 825–32. doi:10.1111/j.1471-4159.2005.03615.x. PMID 16405502. S2CID 23689125.
  22. ^ Martin M, Clare L, Altgassen AM, Cameron MH, Zehnder F (January 2011). "Cognition-based interventions for healthy older people and people with mild cognitive impairment". The Cochrane Database of Systematic Reviews (1): CD006220. doi:10.1002/14651858.cd006220.pub2. PMID 21249675.
  23. ^ Ooi CP, Loke SC, Yassin Z, Hamid TA (April 2011). "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): CD007220. doi:10.1002/14651858.cd007220.pub2. PMC 7388979. PMID 21491398.
  24. ^ a b Saul, Helen (2020-10-23). "People with mild memory problems are left in limbo between health and dementia, and need help to make lifestyle changes". NIHR Evidence (Plain English summary). National Institute for Health and Care Research. doi:10.3310/alert_42131. S2CID 241882442. Retrieved 2022-12-05.
  25. ^ a b Poppe, Michaela; Mansour, Hassan; Rapaport, Penny; Palomo, Marina; Burton, Alexandra; Morgan-Trimmer, Sarah; Carter, Christine; Roche, Moïse; Higgs, Paul; Walker, Zuzana; Aguirre, Elisa; Bass, Nicholas; Huntley, Jonathan; Wenborn, Jennifer; Cooper, Claudia (1 July 2020). "" Falling through the cracks "; Stakeholders' views around the concept and diagnosis of mild cognitive impairment and their understanding of dementia prevention". International Journal of Geriatric Psychiatry. 35 (11): 1349–1357. doi:10.1002/gps.5373. ISSN 0885-6230. PMID 32608171. S2CID 220288902.
  26. ^ Feng, Lei; Cheah, Irwin Kee-Mun; Ng, Maisie Mei-Xi; Li, Jialiang; Chan, Sue Mei; Lim, Su Lin; Mahendran, Rathi; Kua, Ee-Heok; Halliwell, Barry (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. S2CID 73512492.
  27. ^ Feldman HH, Ferris S, Winblad B, et al. (2007). "Effect of rivastigmine on delay to diagnosis of Alzheimer's disease from mild cognitive impairment: the InDDEx study". Lancet Neurol. 6 (6): 501–12. doi:10.1016/S1474-4422(07)70109-6. PMID 17509485. S2CID 10742472.
  28. ^ Birks JS, Harvey RJ (June 2018). "Donepezil for dementia due to Alzheimer's disease". Cochrane Database Syst Rev. 2018 (6): CD001190. doi:10.1002/14651858.CD001190.pub3. PMC 6513124. PMID 29923184.
  29. ^ Petersen, R. C. (September 2004). "Mild cognitive impairment as a diagnostic entity". Journal of Internal Medicine. 256 (3): 183–194. doi:10.1111/j.1365-2796.2004.01388.x. ISSN 0954-6820. PMID 15324362.
  30. ^ Petersen, R. C.; Caracciolo, B.; Brayne, C.; Gauthier, S.; Jelic, V.; Fratiglioni, L. (March 2014). "Mild cognitive impairment: a concept in evolution". Journal of Internal Medicine. 275 (3): 214–228. doi:10.1111/joim.12190. ISSN 0954-6820. PMC 3967548.
  31. ^ "Alzheimer's Disease Facts and Figures 2024" (PDF). Alzheimer's Association. 2024.
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