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Understanding Dementia

Impaired Function

This is an excerpt from the book Understanding Dementia, which is meant to be a practical manual for primary care physicians and other health care professionals. Dementia exists when impairment with cognition (e.g. memory , language, calculation) is severe enough to interfere with function. Thus the assessment of function is an essential aspect of an assessment for dementia. It is discussed in Chapter 5. (In the preface to the book the authors acknowledge the pioneering work of Dr. Barry Reisberg of New York University in relating the staging of dementia to the degree of functional impairment and to changes in the brain. The relevance of his work is especially clear in this excerpt.)

How do the impairments affect function?

Besides the presence of cognitive impairments the diagnosis of dementia also requires that the impairments lead to a decline in social, work or home function. It is worthwhile to spend some time exploring function and changes the patient has made in their usual routine, as some of the most convincing evidence for a diagnosis of dementia comes from this area. Function must be explored with the patient and family. Often decline has been noticeable for some time and innocently ascribed to aging; to be polite, families often minimize the problems and therefore will need to be drawn out during the interview. The FAST (Functional Assessment Staging Tool), developed by Dr Barry Reisberg and colleagues at New York University, provides a useful tool with which to assess function (see Table 5.4). For patients who are still working, problems noticed on the job can be discussed. It is often helpful to ask about changes: are there any tasks that are more difficult now than before? As always corroborating evidence is particularly important: have coworkers noticed any warning signs? For patients who are at home their ability to maintain the household and themselves can be explored.

Rockwood & MacKnight, 2001. p. 85

The FAST is divided into seven stages , ranging from no functional loss (stage 1) through subjective loss only (stage 2) to impairment only in demanding situations (stage 3) which is compatible with, though not sufficient for, a diagnosis of dementia. Typical abnormalities reported at this stage would be the fire inspector who now needs to look up the building codes, or the bank manager who must brief himself on loan regulations before a meeting, where previously they were second nature. In mild dementia (stage 4) difficult everyday tasks, such as managing finances or a multicourse dinner, are impaired. In the later stages of dementia problems with function become more obvious. Requiring prompting to change clothing, difficulty with dressing, toileting, and manipulating a knife and fork occur in the middle stages (stage 5 and early stage 6).

In later stages of untreated dementia, patients typically develop incontinence , difficulty walking, and eventually are unable to speak, smile, and finally swallow (late stage 6 and stage 7). Again, it is important to identify the degree of change from the individual's premorbid level of function, the onset and duration of decline, and corroborate self-reported function with an informant's observations. Often the family will be unwilling to discuss their observations openly in the patient's presence; a telephone call or quick private conversation can be invaluable. Discussion with the family is crucial. In our experience, occasions when we have missed the diagnosis of dementia have typically been due to lack of communication with the family. If no family members are present, we usually seek the patient's permission to make contact.

The FAST has several other uses. It gives a rough guide to the expected duration of each stage in Alzheimer's disease . This information can be used to help the family plan for the future. A table correlating MMSE scores with function is also available (see Table 5.5); its chief use arises when correlation is not present; for example, when the score is low and the patient and family report normal function, closer inquiry to identify deficits is necessary. Questions we have found useful are to ask the family members if they feel comfortable driving with the patient, or, if they were going away, would they arrange for someone to check in on their relative regularly?

Rockwood & MacKnight, 2001. p. 86

If cognitive impairment that interferes with function is dementia, what about cognitive impairment that does not interfere with function? How to understand those cases in which cognitive impairment exists without evident functional impairment can be difficult. Several possibilities exist for the present state: the cognitive impairment is isolated and truly does not impact on function. The cognitive impairment is not truly isolated to memory, and more diligent inquiry will reveal mild impairment in other aspects of higher cortical function, but these still do not impact on function; and the cognitive impairment, whether isolated to memory or not actually interferes with function, a fact that can be revealed by more diligent testing of function. The future state is a bit easier; either the problem will progress to dementia, or it won't.

For now, we can think of a couple of constructs to describe the above cases, as well as a couple of strategies on how to proceed. The truly isolated, largely non-progressive problem with memory, which does not interfere with function, can be thought of as Age-Associated Memory Impairment. While it can progress to dementia, it generally does not, and it is not at all clear that the act of seeking a physician's opinion about the problem distinguishes it from the very common experience of people who find that, as they grow older, they have increasing problems with remembering, especially remembering names. As a rule, the AAMI strategy is to corroborate that there is no impact on function, and then to follow up: time is the best test. This view is likely to become increasingly unfashionable as pressure mounts to provide pharmacological therapy for this problem. Indeed, we seem likely to return to (if not to learn from) an earlier and outmoded "cut points" debate, which was engaged in with great vigour regarding the "interpretation" of test scores on cognitive screening instruments such as the MMSE. Elaborate tables and equations were constructed to define MMSE cut points which, adjusting for age and the patient's level of education, would signify dementia. But as we have noted, the diagnosis of dementia requires the demonstration of both cognitive and functional impairment, in an individualized clinical judgement. So too in our view does a diagnosis of AAMI or its progeny (especially Mild Cognitive Impairment

Mild cognitive impairment (MCI) is a condition that causes a person to have problems with memory, language, or another mential function. For the difficulty to be considered MCI, the problem must be considered severe enough to be noticeable to other people and to show up on tests, but not serious enough to interfere with daily life.

- MCI - the term which appears to be winning out. The term AAMI has merit in describing changes seen with aging which do not proceed to dementia, but this course cannot be known at the outset). Importantly as well, the real test of any treatment in AAMI/MCI will not be whether there is transient (or otherwise) improvement in memory, but should turn on the rather more important question of whether such treatment decreases (or otherwise) the risk of dementia.

In some patients, the physician will suspect that the problem goes beyond memory, or the patient cannot be reassured that by the physician that the problem is isolated to memory. In such cases, specialist physician referral or referral for neuropsychological testing can be helpful.

A second case, where the cognitive impairment goes beyond memory to impair other aspects of cognition, but where there is no persuasive evidence that function has been affected, is statistically more likely to progress to dementia. Just how likely it is to progress, and over what time period it is likely to progress remains unclear. Again, there are two possibilities: follow up, or neuropsychological testing. In our practice, where we have readily reasonable access, we favour the latter.

Taken from Understanding Dementia: A Primer of Diagnosis and Management
Kenneth Rockwood & Chris MacKnight, 2001
Chapter 4, pp 57-63


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Last updated April 12, 2014
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