Letters to the Editor
Down Syndrome and Incidence of Alzheimer's Disease
Am Fam Physician. 1998 Apr 1;57(7):1498.
to the editor: I disagree with several of the comments regarding patients with Down syndrome in the article on adults with mental retardation.1
First, although the Health Care Guidelines for Individuals with Down Syndrome2 are referenced later in the article, they are not listed among the major health supervision guidelines for children and adults with Down syndrome. This publication is, in fact the original set of guidelines and is updated every few years. Although the guidelines are similar to those of the American Academy of Pediatrics, there are differences.
Second, in regard to hematologic disease, an annual complete blood count is no longer recommended by either of the guidelines.
Third, and most important, Table 1 states that early Alzheimer's disease occurs in “almost 100 percent” of Down syndrome patients over 40 years old. The literature states that although the neuropathology does develop in virtually all brains of people with Down syndrome over the age of 35, the clinical appearance of Alzheimer's disease is consideraly less than 100 percent.3 People with Down syndrome age more quickly and therefore develop Alzheimer's disease earlier, but not 100 percent of the time. A colleague of mine had taken care of a woman with Down syndrome who did not have Alzheimer's disease and who died at the age of 83.
The belief that all individuals with Down syndrome will develop dementia is unfortunate. As a result, adults with deteriorating skills are frequently labeled as having dementia when they actually have secondary causes. In one series,4 most such people did not have dementia but instead had depression or adjustment reactions; a smaller number had hypothyroidism. There have even been instances in which a person was believed to have Alzheimer's disease when he or she had conditions such as symptomatic atlantoaxial instability and alcoholism. The article correctly points out that other reversible causes should first be ruled out, including pseudodementia. I would also include abuse as an important consideration, given its high incidence in individuals with disabilities.
Because expressive speech, in particular, is impaired in many people with Down syndrome, they frequently are not able to adequately express their fears or pain. Painful or frightening medical conditions such as gall-bladder disease, seizures and arthritis can be associated with a significant amount of depression or an adjustment reaction that sometimes is confused with dementia. Diagnosis requires a careful history and suspicion for common illnesses as well as those more specific to individuals with Down syndrome. Although the signs and symptoms may be subtle, reversible causes of dementia should be ruled out.
1. Martin BA. Primary care of adults with mental retardation living in the community. Am Fam Physician. 1997;56:485–94.
2. Cohen WI. Health care guidelines for individuals with Down syndrome (Down syndrome preventative medical check list). Down Synd Q. 1996;1(2):1.
3. Zigman WB, Schupf N, Sersen E, Silverman W. Prevalence of dementia in adults with and without Down syndrome. Am J Ment Retard. 1996;100:403–12.
4. Chicoine B, McGuire D, Hebein S, Gilly D. Development of a clinic for adults with Down syndrome. Ment Retard. 1994;32:100–6.
editor's note: This letter was sent to the author of “Primary Care of Adults with Mental Retardation Living in the Community,” who declined to reply.
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