It has recently been found that Alzheimer Disease (AD) is more common in people with Down syndrome (DS) than the general population. Estimates vary, but approximately 10 to 25 percent of individuals with Down syndrome between the ages of 40-49 show clinical signs of AD. As an individual ages, the risk for developing the disease rises. It is further estimated that 20 to 50 percent of 50-59 year olds who have Down syndrome have AD and 60 to 75 percent of those 60 years of age and older have the disease.
While some researchers claim that Alzheimer Disease is a guarantee for those with Down syndrome over 65, one case study reveals that this isn’t necessarily true.
A research scientist at the New York State Institute for Basic Research in Developmental Disabilities is currently focusing on a 70-year-old man, with Down syndrome who has no signs of Alzheimer Disease. The institute has followed the man for 16 years. It is important to note that the average life-expectancy for those with Down syndrome is the late 50s.
Down syndrome is a genetic disorder in which a person inherits three copies of Chromosome 21, instead of just two. Most often setting those children with Down syndrome apart from their peers are their distinct facial appearances including flattened facial features, protruding tongue, small head, upward slanting eyes, and unusually shaped ears.
Alzheimer Disease is a progressive brain disorder that affects memory, intelligence, judgment, language, and behavior. It is the most common form of dementia, which is not a specific disease, but rather a term to describe a wide range of symptoms related to a decline in memory or thinking skills that affects a person’s daily activities.
In the general population, the risk for developing the disease is about one in eight for people over the age of 65. Once diagnosed with AD, individuals live an average of eight years. However, depending on a person’s age and health conditions, that life expectancy can range between two and 20 years.
Alzheimer Disease accounts for 60 to 80 percent of dementia cases. Other causes of dementia symptoms include stroke, thyroid problems, and vitamin deficiencies.
It is not completely known why Alzheimer Disease is more common in individuals with Down syndrome. What is known is that AD is associated with an increased production of a compound called beta amyloid in the brain, and the extra copy of chromosome 21 leads to an increased production of beta amyloid.
The accumulation of beta amyloid causes the loss of neurons, or brain cells, thus leading to a decrease in brain functioning.
For those with Down syndrome, symptoms of Alzheimer Disease generally first appear in the mid- to late-40s or early 50s, with the average age of diagnosis being 52. From the time the first symptoms are noticed, the person’s life expectancy is about nine years.
People in the general population generally do not experience symptoms until their late 60s. The reason for this difference is that people with Down syndrome experience premature aging, showing the physical signs of aging about 20 to 30 years ahead of people the same age in the general population.
Early symptoms include: (It is important to note that many of these first symptoms are not always recognized as AD.)
Behavioral changes such as refusing to follow directions or do chores.
Changes in daily routine, sleeping or eating habits
Inability to make decisions about clothing, getting lost in familiar settings, not remembering the names of familiar people
Inability to perform job duties
Learning is generally impaired
Loss of language or other communication skills
Impairment of social skills
Progressive loss of activities of daily living (ADL), such as personal hygiene, dining skills and bathroom skills
Middle stage symptoms:
ADL significantly deteriorates and the patient may depend totally on other for assistance with dressing, eating, and toilet needs
Behavioral problems increase
Psychotic behavior may develop
Social activities are greatly reduced
Advanced stage symptoms:
Total dependence on others for their care
Minimal interaction with their surroundings
The early stages of Alzheimer Disease is often difficult to detect in people with Down syndrome as they have a wide array of health problems, which can mimic or hide the presence of the disease. Alzheimer-type symptoms can arise from other conditions such as chronic ear and sinus infections, sleep apnea, thyroid disorders, clinical depression, brain tumor, recurrent brain strokes, metabolic imbalances and various neurological conditions, so it is important to rule these out as possible outcomes to the symptoms.
In addition, the typical tests used to diagnose Alzheimer Disease in the general population typically cannot be used on individuals with Down syndrome due to various reasons including limited verbal and other communication skills that many make assessment difficult.
Instead several assessments have been designed to diagnose the disease in individuals with Down syndrome which focus on changes in activities of daily living such as dressing, eating, and bathing.
There is no cure for Alzheimer Disease, and despite treatment, the disease still progresses and worsens. Medication can often help slow the progression, but the medication must begin as early as possible. If AD isn’t diagnosed for persons with Down syndrome until the middle to late stages, medications generally are not effective.
The main reason for medical treatment is to treat the signs and symptoms of dementia or the behavioral changes that are also taking place such as psychosis, anxiety, and depression.
Research is currently underway on the medication known as mematine, or its brand name Namenda. Early results indicate that the drug could boost cognitive function in patients who have Alzheimers and possibly, help people who have Down syndrome as well.
Because amyloid, a protein found in the brain of individuals with AD, has also been found in the brains of adults with Down syndrome, researchers are focusing on brain imaging techniques to help with detection and differentiating other forms of cognitive changes.
The July issue of Archives of Neurology explains that when researchers compared the brains of dementia-free DS patients with the brains of AD patients, the results are very similar. The most notable difference was the location of the highest levels of the amyloid protein were in the frontal lobe of the brain, which is associated with behavior, memory, and reasoning. This is a possible explanation for why changes in a DS patient's personality occur earlier in DS-related dementia than in Alzheimer's.
One current study is amyloid imaging, which is under development for the early detection of Alzheimer Disease. The research is aimed at discovering which adults with Down syndrome are at risk for developing AD before any changes happen in their thinking and functioning. The imaging will help catch the disease at its earliest stages.
Another study is FDG PET imaging where the scans detect changes in the metabolism of the brain which could represent Alzheimer Disease. It is the hope that this test will distinguish the difference between Alzheimer Disease and other cognitive changes.
For more information about these studies visit the Institute for Neurodegenerative Disorders.