Synonym: mild neurocognitive disorder
Mild cognitive impairment (MCI) is common. MCI is defined as the symptomatic pre-dementia stage on the continuum of cognitive decline, characterised by objective impairment in cognition that is not severe enough to require help with the usual activities of daily living.
The National Institute for Health and Care Excellence (NICE) recommends that early assessment should take place in order to enable planning for the future or, if treatment is to be given, to enable its institution at an early stage. They also recommend that a memory assessment service should be the single point of referral for all patients with a possible diagnosis of dementia.
It is difficult to obtain accurate figures, as not everyone with decline of memory will present with symptoms. Prevalence and incidence estimates associated with MCI vary greatly.
One review found the prevalence of MCI in adults aged 65 years and older to be 10-20%, with increased risk with increasing age and with men appearing to be at higher risk than women.
An individual may present complaining of loss of memory; however, very often it is not the patient but a family member who makes the complaint. This may cause some difficulty for the doctor if the patient is reluctant to admit that there is a problem.
Whilst the autonomy of the individual is to be respected, forgetfulness may put both the patient and others at risk. Forgetting to turn off a cooker or a fire at night may cause a fire. Leaving the gas on but unlit may cause an explosion. A common cause for concern is the ability to drive. See separate Supporting the Family of People with Dementia article.
Criteria for the diagnosis of MCI
- Concern regarding a change in cognition from the patient, a knowledgeable informant, or from a skilled clinician observing the patient.
- Objective evidence of impairment (from cognitive testing) in one or more cognitive domains, including memory, executive function, attention, language, or visuospatial skills.
- Preservation of independence in functional abilities (although individuals may be less efficient and make more errors at performing activities of daily living).
- No evidence of a significant impairment in social or occupational functioning (ie not dementia).
Clinical characteristics suggesting that MCI is due to Alzheimer's disease
- Memory impairment present.
- Progressive decline in cognition over months to years (very rapid decline may suggest prion disease, neoplasm or metabolic disorders).
- Lack of Parkinsonism and visual hallucinations (suggestive of dementia with Lewy bodies).
- Lack of vascular risk factors and extensive cerebrovascular disease on brain imaging (suggestive of vascular cognitive impairment).
- Lack of prominent behavioural or language disorders (suggestive of frontotemporal lobar degeneration).
Assessing cognitive impairment
See separate Screening for Cognitive Impairment article. Several tools are available:
- The Mini Mental State Examination (MMSE) - this was developed by psychiatrists and is widely regarded as the 'gold standard' test for dementia.
- Six-item Cognitive Impairment Test (6CIT) - the Kingshill test - this was developed in 1983 by regression analysis of a more detailed assessment, the Blessed Information Memory Concentration (BIMC) Scale.
- The Abbreviated Mental Test (AMT) - this was developed by geriatricians and is probably the best known score test in general hospital usage.
The 6CIT is probably the best compromise between specificity, sensitivity and ease of use. The validity of the AMT score has been questioned in the multicultural environment of primary care but can be adapted for use in such a setting.
For more information, see separate Screening for Cognitive Impairment article.
Although some decline in memory may be seen as normal with advancing years, it may also be due to other factors and they may be treatable, although this is by no means true of them all.
- By far the most common cause of significant cognitive impairment is Alzheimer's disease and, although it is characteristically a disease of old age, it can strike quite young. Mild impairment can precede serious cognitive dysfunction by many years.
- Some of the other dementias also tend to strike in middle age.
- Some women may become forgetful around the time of the menopause.
There are many factors that may influence cognitive decline:
- Cerebrovascular events.
- Hyperparathyroidism, hypoparathyroidism.
- Hypoperfusion - eg, heart failure.
- Head trauma, including recurrent trauma of having been a boxer.
- Deficiencies of folate, vitamin B12 and vitamin B6 are associated with neurological and psychological dysfunction and are potential factors for cognitive impairment and the development of dementia in the elderly.
- Open heart surgery with cardiopulmonary bypass.
- Medication use, especially sedatives.
- Hepatic impairment.
- Sleep disorders - eg, obstructive sleep apnoea.
- Psychological stress.
- Drug or alcohol abuse.
- Toxins, infections, metabolic (eg, hypoglycaemia) and structural causes.
Homocysteine is a risk factor for cerebrovascular disease and may also have directly toxic effects on neurons of the central nervous system. Hyperhomocysteinaemia has been suggested as a cause or mechanism in the development of Alzheimer's disease and other forms of dementia.[6, 7]
More subtle causes which may be present in a large proportion of the elderly, and the not so elderly, population include:
- Oestrogen decline - there is evidence that postmenopausal oestrogen levels have a negative correlation with the risk of cognitive decline.
- High corticosteroid levels in older people - associated with cognitive decline.
There are many causes of dementia and in the early stages they will present with MCI. The following list is far from all-inclusive:
- MCI is common in patients with Parkinson's disease and frequently progresses to dementia.
- Dementia with Lewy bodies is second only to Alzheimer's disease as a common cause of dementia.
- Pick's disease (frontotemporal dementia).
- Huntington's chorea.
- Multiple sclerosis.
- Creutzfeldt-Jakob disease.
- Heavy metal poisoning and carbon monoxide poisoning.
A complaint of impaired memory is common and may or may not be pathological. A stepwise approach to investigation is required.
Routine investigations to assist in ruling out physical causes should include:
- Full history, especially with respect to past medical history, family history, drug and social history.
- Full examination, looking especially for possible cardiac or neurological abnormalities.
- An assessment of cognition using one of the tools outlined above.
- Laboratory tests - FBC, U&Es, LFTs, calcium and vitamin B12 levels, TFTs and random or fasting blood sugar.
The assessment of cognitive impairment which is not associated with any physical illness or structural abnormality relies on specialised tests which assess function independently of structure and may include:
- Neuropsychological testing.
- Electroencephalogram and evoked potentials.
- Functional imaging, CT scan, positron emission tomography (PET) scan, MRI scan, magnetoencephalography.
There is currently no medication that is recommended for treating MCI.
The Alzheimer's Society recommends the following non-drug strategies to cope with memory loss:
Coping with everyday life
- Keep track by making 'to do' lists of tasks.
- Break up tasks into bite-sized chunks to make them more manageable.
- Try to do one thing at a time - tackling too many things at once can be confusing.
- Try to have a routine to give structure to your day and to help you remember what you are supposed to be doing.
- Take your time - there's no hurry.
- Use clocks, wear a watch, put up a calendar and think about taking a daily newspaper to help you to keep track of time.
- Consider keeping a diary in which you can note down appointments, 'to do' lists and anything else you want to remember.
- Use sticky-backed notes to help remind you of things you have to do.
- Keep important things such as money, keys or spectacles in the same place, so you always know where to find them.
- Keep important telephone numbers by the telephone so they are always on hand.
- Arrange to pay regular bills by direct debit or standing order.
- Try not to be embarrassed if you forget something.
- If the right word or piece of information escapes you, don't try too hard. Once you stop trying it will often pop into your head.
- We all need help from time to time and other people are usually only too happy to be asked. Talk to family and friends about how they can help to support you.
- An occupational therapist may be able to help with devising strategies and using memory aids.
- Take regular exercise.
- Stop smoking.
- Ensure adequate but not excessive sleep.
There is some evidence that cognitive interventions (memory training) do lead to performance gains but the improvements have not exceeded the improvements seen in active control conditions.
There are no rigid criteria for referring patients for specialist assessment. Referral is appropriate when it is suspected that the cognitive impairment is more than just minor, and/or the cognitive impairment is suspected to be part of a wider picture of dementia which may require specialist intervention (eg, pharmacological intervention).
NICE recommends taking the following into consideration when assessing a possible diagnosis of dementia in primary care:
- The individual's self-report of changes in memory, capability or mood.
- Informant histories that support self-report and add significant new details of changes.
- Exclusion of depression and delirium as primary pathologies, using the information from the personal and informant histories.
- Measurable cognitive losses, using a standardised instrument.
- Absence of 'red flag' symptoms, suggesting alternative diagnoses (for example, urinary incontinence or ataxia in apparent early dementia).
They also recommend considering referring patients who show signs of MCI, and an increased awareness of the risk of dementia in patients with learning disabilities, or a history of Parkinson's disease, stroke, or other neurological conditions.
MCI can act as a transitional level of evolving dementia with a risk of developing dementia of 10-15% per year.
The modification of risk factors, such as stopping smoking and correcting vitamin deficiencies, can prevent cognitive decline in the elderly.
- Healthy living, with good control of cardiovascular risk factors, especially blood pressure, is important. Angiotensin-converting enzyme (ACE) inhibitors and angiotensin-II receptor antagonists may improve cognitive function in the elderly.
- Omega-3 fatty acids have been reported to have a role in the prevention of dementia. However, direct evidence on the effect of omega-3 polyunsaturated fatty acids (PUFA) in the prevention of dementia is lacking. Trials have shown no benefit of omega-3 PUFA supplementation on cognitive function in cognitively healthy older people.
- Excessive alcohol consumption should be avoided. Higher educational achievement also seems to give some protection but this may be related to people of higher education remaining mentally more active in retirement.
The concept of use it or lose it is as pertinent to the mind as it is to the body.
Further reading and references
; NICE CKS, April 2015 (UK access only)
; The diagnosis and management of mild cognitive impairment: a clinical review. JAMA. 2014 Dec 17312(23):2551-61. doi: 10.1001/jama.2014.13806.
; NICE Clinical Guideline (November 2006, last updated September 2016)
; Mild cognitive impairment: disparity of incidence and prevalence estimates. Alzheimers Dement. 2012 Jan8(1):14-21. doi: 10.1016/j.jalz.2011.01.002.
; Mild Neurocognitive Disorder: An Old Wine in a New Bottle. Harv Rev Psychiatry. 2015 Sep-Oct23(5):368-76. doi: 10.1097/HRP.0000000000000084.
; Screening for cognitive impairment among older people in black and minority ethnic groups. Age Ageing. 2004 Sep33(5):447-52. Epub 2004 Jun 24.
; B vitamins and the aging brain. Nutr Rev. 2010 Dec68 Suppl 2:S112-8. doi: 10.1111/j.1753-4887.2010.00346.x.
; The effect of vitamin B6 on cognition. Cochrane Database Syst Rev. 2003(4):CD004393.
; Endogenous oestrogens are related to cognition in healthy elderly women. Clin Endocrinol (Oxf). 2005 Jul63(1):50-5.
; Urinary cortisol excretion as a predictor of incident cognitive impairment. Neurobiol Aging. 2005 Dec26 Suppl 1:80-4. Epub 2005 Nov 8.
; Cognitive impairment in patients with Parkinson's disease: diagnosis, biomarkers, and treatment. Lancet Neurol. 2012 Aug11(8):697-707. doi: 10.1016/S1474-4422(12)70152-7.
; Diagnostic evaluation of elderly patients with mild memory problems. Ann Intern Med. 2003 Mar 4138(5):411-9.
; Mild cognitive impairment: diagnosis, longitudinal course, and emerging treatments. Curr Psychiatry Rep. 2014 Oct16(10):490. doi: 10.1007/s11920-014-0490-8.
; Cognition-based interventions for healthy older people and people with mild cognitive impairment. Cochrane Database Syst Rev. 2011 Jan 19(1):CD006220. doi: 10.1002/14651858.CD006220.pub2.
; Mild cognitive impairment and its management in older people. Clin Interv Aging. 2015 Apr 1010:687-93. doi: 10.2147/CIA.S73922. eCollection 2015.
; Prevention of Alzheimer disease. Encouraging evidence. Can Fam Physician. 2006 Feb52:200-7.
; Effect of antihypertensive agents on quality of life in the elderly. Drugs Aging. 200421(6):377-93.
; Omega 3 fatty acid for the prevention of cognitive decline and dementia. Cochrane Database Syst Rev. 2012 Jun 136:CD005379. doi: 10.1002/14651858.CD005379.pub3.