Mild memory loss is also known as mild cognitive impairment (MCI). It is a common phenomenon which affects all of us at times. It is not the same as dementia.

The challenge for the GP is to recognise more serious memory loss - reported by the patient or by a relative - which may be a precursor of overt dementia.

The National Institute for Health and Clinical Excellence (NICE) recommends that early assessment should take place, 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.¹ NICE has recently produced commissioning guidance, which emphasises the need for integrated and quality-assured local memory assessment services.²

Epidemiology

It is difficult to obtain accurate figures, as not everyone with decline of memory will present with symptoms:

• Some groups have a higher frequency of memory complaints, e.g. individuals with low educational achievement.³ Women are also more likely to report memory loss than men.
• Many older people complain of mild memory loss, and do less well than their young counterparts in tasks which assess memory.

It is assumed that mild memory impairment is a common, even normal, consequence of the ageing process. Longitudinal studies in the elderly have revealed a gradual decline in the cognitive abilities of older people, but differences between individuals in the rate of decline suggest that at least some of this age-related deterioration is due to the inclusion of subjects with incipient dementia.⁴ The suggestion that elderly people may demonstrate an incipient phase for Alzheimer's disease (AD) is supported by studies in the elderly which have shown evidence of AD years before clinical symptoms are evident, and this is more common in individuals with memory impairment.⁵

Although mild memory impairment is very common in the ageing population, it becomes abnormal when it has an impact on a person's ability to function normally on a day-to-day basis.

Presentation

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. This is discussed in the separate article Help and Advice for Relatives of Demented Patients.

Assessing memory loss

A number of 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 AMTS has been questioned in the multicultural environment of primary care, but can be adapted for use in such a setting.⁶

For more information, see separate article Screening for Cognitive Impairment.

Causes of memory impairment

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 impairment of memory is Alzheimer's disease (AD) and, although it is characteristically a disease of old age, it can strike quite young. Mild impairment can precede serious cognitive disfunction by many years.⁵
• Some of the other dementias also tend to strike in middle age.
• Around the menopause, some women get forgetful and make lists to remind themselves.

There are many factors that may influence cognitive decline:⁷

• Cerebrovascular events
• Hypothyroidism
• Hyperparathyroidism
• Hypoperfusion
• Head trauma, including recurrent trauma of having been a boxer
• Open heart surgery with cardiopulmonary bypass
• Medication use
• Hepatic impairment
• Depression
• Drug or alcohol abuse
• Toxins, infections, metabolic and structural causes

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 risk of cognitive decline⁸
• High corticosteroid levels in older people - associated with cognitive decline⁹
• Testosterone decline - may be relevant but evidence is not strong¹⁰
• Mesiotemporal sclerosis

Associated diseases

There are many causes of dementia and in the early stages they will present with mild memory loss. The following list is far from all-inclusive:

• About 20% of patients with Parkinson's disease (PD) also develop dementia
• Dementia with Lewy bodies is second only to Alzheimer's disease (AD) as a common cause of dementia
• Pick's disease (frontotemporal dementia)
• Huntington's chorea
• Syphilis
• AIDS
• Multiple sclerosis
• Creutzfeldt-Jakob disease
• Heavy metal poisoning and carbon monoxide poisoning

Investigations

A complaint of impaired memory is common and may or may not be pathological. A stepwise approach to investigation is required.¹¹

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, thyroid function tests, and random or fasting blood sugar.

The assessment of memory impairment which is not associated with any physical illness or structural abnormality relies on specialist tests which assess function independently of structure and may include:

• Neuropsychological testing
• Electroencephalogram and evoked potentials
• Functional imaging, CT scan, PET scan, MRI scan, magnetoencephalography

Management

The Alzheimer's Society recommends the following nondrug strategies to cope with memory loss:¹²

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.

Memory aids

• 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.

General health

• Take regular exercise.
• Stop smoking.
• Ensure adequate but not excessive sleep.

Referral criteria

There are no rigid criteria for referring patients for specialist assessment. Referral is appropriate when it is suspected that the memory loss is more than just minor, and/or the memory loss is suspected to be part of a wider picture of dementia which may require specialist intervention (e.g. pharmacological intervention).

NICE recommends taking the following into consideration when assessing a possible diagnosis of dementia in primary care:¹

• 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 mild cognitive impairment, 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.

Prognosis

Of those with mild cognitive impairment, about 15% per annum will progress to dementia and 90% of this will be Alzheimer's disease (AD).¹³
Hence, it seems fair to assume that mild but significant cognitive impairment probably represents the early stage of some form of dementia. If treatment for the condition is to be effective, it needs to be started at an early stage. Hence the need for early diagnosis.

Prevention

• Healthy living, with good control of cardiovascular risk factors, especially blood pressure, is important.^14,15 Angiotensin-converting enzyme (ACE) inhibitors and angiotensin II antagonists may improve cognitive function in the elderly.¹⁶
• There is increasing evidence of the value of omega-3 fatty acids in prevention of dementia but no evidence from RCTs.¹⁷
• Excessive alcohol consumption should be avoided. Higher education 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.

Document references

1. Dementia: Supporting people with dementia and their carers in health and social care, NICE Clinical Guideline (2006)
2. NICE Commissioning Guide; Memory assessment service for the early identification and care of people with dementia, December 2007
3. DeCarli C; Mild cognitive impairment: prevalence, prognosis, aetiology, and treatment.; Lancet Neurol. 2003 Jan;2(1):15-21. [abstract]
4. Wilson RS, Beckett LA, Bennett DA, et al; Change in cognitive function in older persons from a community population: relation to age and Alzheimer disease.; Arch Neurol. 1999 Oct;56(10):1274-9. [abstract]
5. Morris JC, Storandt M, Miller JP, et al; Mild cognitive impairment represents early-stage Alzheimer disease.; Arch Neurol. 2001 Mar;58(3):397-405. [abstract]
6. Parker C, Philp I; Screening for cognitive impairment among older people in black and minority ethnic groups. Age Ageing. 2004 Sep;33(5):447-52. Epub 2004 Jun 24. [abstract]
7. Small SA; Age-related memory decline: current concepts and future directions.; Arch Neurol. 2001 Mar;58(3):360-4. [abstract]
8. Lebrun CE, van der Schouw YT, de Jong FH, et al; Endogenous oestrogens are related to cognition in healthy elderly women.; Clin Endocrinol (Oxf). 2005 Jul;63(1):50-5. [abstract]
9. Karlamangla AS, Singer BH, Chodosh J, et al; Urinary cortisol excretion as a predictor of incident cognitive impairment.; Neurobiol Aging. 2005 Dec;26 Suppl 1:80-4. Epub 2005 Nov 8. [abstract]
10. Kenny AM, Bellantonio S, Gruman CA, et al; Effects of transdermal testosterone on cognitive function and health perception in older men with low bioavailable testosterone levels.; J Gerontol A Biol Sci Med Sci. 2002 May;57(5):M321-5. [abstract]
11. Karlawish JH, Clark CM; Diagnostic evaluation of elderly patients with mild memory problems.; Ann Intern Med. 2003 Mar 4;138(5):411-9. [abstract]
12. Alzheimer's Society. Worried About Your Memory; 2007; Patient information sheet.
13. Celsis P; Age-related cognitive decline, mild cognitive impairment or preclinical Alzheimer's disease? Ann Med. 2000 Feb;32(1):6-14. [abstract]
14. Small GW; What we need to know about age related memory loss. BMJ. 2002 Jun 22;324(7352):1502-5.
15. Scalco MZ, van Reekum R; Prevention of Alzheimer disease. Encouraging evidence. Can Fam Physician. 2006 Feb;52:200-7. [abstract]
16. Fogari R, Zoppi A; Effect of antihypertensive agents on quality of life in the elderly.; Drugs Aging. 2004;21(6):377-93. [abstract]
17. Lim WS, Gammack JK, Van Niekerk J, et al; Omega 3 fatty acid for the prevention of dementia.; Cochrane Database Syst Rev. 2006 Jan 25;(1):CD005379. [abstract]

Acknowledgements