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Ageing and Dementia

Dementia is the name given to a collection of illnesses, one of which is Alzheimer’s disease, that have a characteristic pattern of symptoms and signs and generally occurs in later life. The main characteristics of several of the dementias is a deterioration in the person’s memory (usually for recent events) and loss of other abilities such as the ability to find one’s way around, to communicate through language and to undertake particular tasks, such as getting dressed. Dementia due to Alzheimer’s disease is a steadily progressive disorder with evidence of decline over time. It is important to stress that this is much more marked than the memory difficulties that many of us are aware of with increasing age! As described above the presence of Alzheimer’s disease is associated with the development of marked plaque and tangle formation in particular areas of the brain.

The key questions with respect to the effects of ageing in people with Down’s syndrome is whether the plaque and tangle changes in the brain are or are not associated with the development of Alzheimer’s disease. Our own work suggests that the characteristic features of dementia do begin to appear in some people with Down’s syndrome with increasing age but not in as many as the brain studies of Down’s syndrome originally suggested would be the case. We have seen 75, of a total of 77 people with Down’s syndrome 30 years or older living in the Cambridge Health District. A small percentage of this group had evidence of dementia in their 30’s, approximately 10% in the 40’s and 40% in their 50’s. This is about the same as you would expect in the general population but 30 or 40 years earlier in life. For us an important research question is to determine why some people with Down’s syndrome live into their 60’s yet do not get Alzheimer’s disease, whereas others do. What might protect some people and what might increase the risk in others?

Apparent decline in later life: Causes to consider

This article has focused on some of the changes which have been described to occur in the brains of people with Down's syndrome as they reach middle and later life. As described above these changes only matter if they affect a person's ability and result in dementia due to Alzheimer's disease. Whilst rates of Alzheimer's disease do increase with age, its development is NOT inevitable. Outlined below and in the Table are some of the other factors that can result in apparent decline, particularly in later life, and which can be treated. This process of identifying the cause of apparent change is therefore critical.

Dementia, whatever its cause, effects a person's cognitive abilities and his/her ability to undertake tasks or to communicate. Whilst a decline in memory or the slow loss of specific abilities may be readily apparent in those without a preexisting disability, it may be less easily noticed in people with Down's syndrome. There are two main reasons for this. First, unless someone has known that person for some time and has observed the changes, the inability to do something is all too easily put down to his/her learning disability. The crucial question, in the case of an older person with Down's syndrome, is has he/she been able to do this in the past and now cannot? If so, why has this change occurred? Secondly, loss of ability may go unnoticed if the person is leading a life where he/she is, for example, not expected to take part in household activities or do tasks that require good memory. The fact that someone's memory may have deteriorated would under these circumstances go unnoticed.

Where there is good and reliable information available about how someone has changed and how he/she is now, the diagnosis of dementia can be made with a high degree of certainty. Those conditions listed in the Table can be excluded either on the basis of the istory or through I investigations. For example, depression can mimic dementia, but has other recognisable symptoms as well. They include a change in ] mood, loss of interest and ability to concentrate, together with changes in sleep and appetite. Thyroid disorders can be excluded both on the basis of clinical features and by a blood test. The decline may be for several reasons and those causes, which can be treated, should be treated. If there is doubt a computerised brain scan (CT or MRI scan) may help by showing evidence or not of brain changes which would normally be expected with ' Alzheimer's disease. Sometimes the reasons ' for change in later life cannot be established with certainty and it is ' necessary to follow-up over time. Detailed psychological tests of memory and other abilities can be particularly helpful in this situation. The most valuable information is invariably that given by those who have known the person over his/her lifetime or at least over many years. There is no substitute for this.

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