The Relationship Between Alzheimers's Disease And Down Syndrome

The Relationship Between Alzheimers's Disease And Down Syndrome

Down syndrome increases the risk of Alzheimer’s disease

People with Down syndrome may experience health problems as they age that are similar to those experienced by older people in the general population. The presence of extra genetic material found among persons with Down syndrome may lead to abnormalities in the immune system and a higher susceptibility to certain illnesses, such as Alzheimer's, leukemia, seizures, cataracts, breathing problems, and heart conditions.

People with Down syndrome also experience premature aging. That is, they show physical changes related to aging about 20 to 30 years ahead of people of the same age in the general population. As a result, Alzheimer's disease is far more common in people with Down syndrome than in the regular population. Adults with Down syndrome often are in their mid to late 40s or early 50s when Alzheimer's symptoms first appear. People in the general population don't usually experience symptoms until they are in their late 60s.

The symptoms of Alzheimer's disease may be expressed differently among adults with Down syndrome. For example, in the early stages of the disease, memory loss is not always noted. In addition, not all symptoms ordinarily associated with Alzheimer's disease will occur. Generally, changes in activities of daily living skills are noted, and the person with Down syndrome may begin to have seizures when he or she never had them before. Changes in mental processes -- such as thinking, reasoning, and judgment -- also may be present, but they often are not commonly noticeable because of limitation of the individual's functioning in general.

Why do people with Down syndrome get Alzheimer’s disease?

Current research shows that the extra "gene dosage" caused by the abnormal third chromosome of Down syndrome might be a factor in the development of Alzheimer’s disease. Interest also is being focused on the early onset of Alzheimer’s disease in individuals with Down syndrome, which might be related to the early aging of the Down syndrome brain.

Down syndrome occurs because a gene error results in three copies instead of 2 of chromosome 21. This chromosome has the gene for the This chromosome has the gene for the protein that causes the disease. The extra "gene dose" causes too much protein to be produced.

How is Down syndrome associated with Alzheimer's disease?

Advances in medical care have resulted in longer life expectancy for people with Down syndrome. Many adults with Down syndrome now live well into their 50s and 60s. Almost all people with Down syndrome who live into their 40s and beyond will develop the abnormal brain changes (the plaques and tangles) that characterize the brain in Alzheimer's disease. It is important to note, however, that not all people with Down syndrome who develop these brain changes will go on to develop dementia. This represents yet another example of the increasing evidence that there is something more than just the plaques and tangles in the Alzheimer brain which is involved in producing dementia. It is possible that aging introduces additional changes which together with the plaques and tangles cause dementia to develop. The fact that the brains of people with Down syndrome are not aged may be one explanation why these individuals will often have the plaques and tangles which in Alzheimer's disease are associated with dementia, but not develop the disease itself.

How Common Is Alzheimer's Disease in People With Down Syndrome?

Estimates suggest that 25% or more of individuals with Down syndrome over age 35 show the signs and symptoms of Alzheimer's-type dementia. The percentage increases with age. The incidence of Alzheimer's disease in people with Down syndrome is estimated to be three to five times greater than that of the general population.

The link between Down Syndrome anf Alzheimer's Disease

Studies show that by the age of 40, almost 100% of people with Down syndrome who die have the changes in the brain associated with Alzheimer’s disease. Amyloid precursor protein (APP), which is the abnormal breakdown that yields the toxic amyloid protein that forms plaques in the brain and probably damages brain cells and their connections, is coded for chromosome 21. Because people with Down syndrome have an extra copy of chromosome 21, they make 1.5 times as much APP as other people, and this seems to result in an excess tendency for the abnormal amyloid breakdown product to build up. This appears to cause earlier appearance of the brain changes typical of Alzheimer’s disease. However, a significant number of people with Down syndrome are older than 40 and show no signs of having Alzheimer’s disease. It is not currently understood why changes to the brain that are typical of Alzheimer’s disease do not necessarily produce the condition in people with Down syndrome.

Things to consider when making a diagnosis of Alzheimer's disease in a person with Down syndrome

Making a diagnosis of Alzheimer's disease can be more difficult when an individual has Down syndrome for the following reasons:

  • Individuals with Down syndrome may have a wide range of health problems associated with aging and these may mimic or mask the presence of Alzheimer's disease.
  • The existing assessment scales for Alzheimer's disease may not be sensitive to the changes in abilities of people with Down syndrome.
  • People with Down syndrome have more limitations in motor, language, communication and intellectual abilities than the average person. As a result, it is often difficult to detect subtle changes in these areas of functioning that are related to the symptoms of Alzheimer's disease rather than Down syndrome.

When individuals have Down syndrome, physicians often find it helpful to rely on caregivers for details of the individual's medical and psychosocial history. Keeping track of changes in the person's abilities can be done by keeping a personal journal. These notes can assist in separating pre-existing symptoms from those resulting from Alzheimer's disease. Caregivers can also report on an individual's changes in social functioning and engagement with others.

The importance of living a full life

Currently, there is no way to prevent the brain changes that may occur in people with Down syndrome. However, leading as full, healthy and active a life as possible may help reduce the risk of developing dementia. This includes keeping up interests in work and recreation, friends and family, maintaining good health, diet and fitness, and having regular medical checkups.

Other conditions that can be treated

People with Down syndrome are susceptible to a number of other physical and mental health issues that lead to a decline in abilities and could be mistaken for dementia. These include hypothyroidism, sleep apnoea, sensory impairments, depression or the side effects of some medications.

If you are concerned about changes in mood, personality, behaviour, learning, memory or skills in doing everyday activities, or other symptoms that you think could indicate the onset of Alzheimer's disease, you should inform the person’s doctor and see a specialist to have these symptoms investigated.

Providing Care

All people with Alzheimer's disease deserve to be treated with dignity and respect. No matter how the disease affects the person, emotions and feelings remain. When an individual has Down syndrome, there are some special considerations that may help in providing care:

  • As with anyone who cares for someone with Alzheimer's disease, it is essential that all caregivers are educated to understand the disease and its unique effects on the individual.
  • Caregivers of a person with Down syndrome may have been providing care for many years and may benefit from additional support as the individual's needs change. This can be especially true if a move to a long-term care facility is being considered.
  • Caregivers of people with Down syndrome may find it helpful to learn to adapt the strategies they have been using and to learn new ways of building on the individual's remaining strengths and abilities.