Alzheimer's Disease International's Fact Sheet on Dementia and Intellectual Disabilities

This fact sheet was developed for use by Alzheimer's International by Dr. Heather Wilkinson of the University of Edinburgh and Dr. Matthew Janicki of the University of Illinois at Chicago. It is also available on ADI's website.

Why the concern about dementia among people with intellectual disabilities?
Dementia is emerging as a significant concern for carers, clinicians and providers involved with adults with intellectual disabilities (ID - a condition of lifelong limited intellectual, social and vocational capabilities). With the aging of many nations' populations, there is also an increasing number of adults with intellectual disabilities who are surviving to old age. As these individuals age, they are at greater risk of presenting with signs and symptoms, like age peers in the general population, indicative of Alzheimer's disease and related dementias. Concerns stem from an increasing incapacitation after a lifetime of progressive learning and development and new care demands placed on families and other carers. Clinicians recognize the need for more diagnostic precision and assessment resources, as well as practices that compensate for decline. Provider organizations have noted the need to adapt homes and residential services and provide appropriate supports for continued community care.

How many people with intellectual disabilities are affected by dementia?
With the exception of adults with Down syndrome, adults with IDs are at the same risk for Alzheimer's disease and related dementias as are other adults in the general population. Generally, adults are at greater risk of developing the disease if they: are age more than 60, have Down syndrome, have had some form of severe or multiple head injury, and have a history of Alzheimer's disease in their family. Population studies show us that the rate of occurrence of Alzheimer's disease and related dementias among persons with ID appears to be about the same as in the general population (or about 6% of persons age 60 and older). The rate among same-age adults with Down syndrome is much higher - about 25% for adults age 40 and older and about 65% for adults age 60 and older. It is estimated that there are more than 150,000 adults with ID worldwide affected by some form of dementia and that this number will triple over the next 20 years.

How are people with Down syndrome affected differently by Alzheimer's disease?
People with Down syndrome have higher rates of Alzheimer's disease. A growing body of research suggests that people with Down syndrome also experience premature aging, perhaps as many as 20 years earlier than other adults. Many are in their mid to late 40s or early 50s when symptoms of Alzheimer's disease first appear, compared to the late 60s for adults with other intellectual disabilities. Not all adults with Down syndrome will exhibit Alzheimer's disease - some may grow old free of any symptoms - and die of other causes.

Although about 20 to 40 percent of adults with Down syndrome show the behavioral symptoms of dementia, upon autopsy nearly all older adults with Down syndrome show the brain changes or neuropathology associated with Alzheimer's disease. Men and women seem to be equally susceptible. The progression of the disease takes, on the average, about eight years - somewhat less time than among persons in the general population. The nature of the disease course generally mirrors that of other people, but is compressed due to the shorter longevity of adults with Down syndrome. Some adults with Down syndrome are susceptible to a particularly aggressive form of Alzheimer's disease - the course of which is from one to three years.

The symptoms of the disease sometimes are expressed differently among adults with Down syndrome. For example, at the early stage of the disease, memory loss is not always noted, and not all symptoms ordinarily associated with Alzheimer's disease will occur. Generally, first observed are changes in activities of daily living skills, and in some adults late-onset seizures may occur. Cognitive changes may also be present, but they are often not readily apparent, or initially they may be ignored because of limitations in the individual's general functional level.

What are some signs that an older person with an intellectual disability may be developing Alzheimer's disease?
Studies of individuals with ID have shown that behavioral symptoms of Alzheimer's dementia may include, but are not limited to: the development of seizures in previously unaffected individuals, changes in personality, loss of memory and general function, long periods of inactivity or apathy, hyperactive reflexes, loss of activity of daily living skills, visual retention deficits, loss of speech, disorientation, increase in stereotyped behavior, and abnormal neurological signs.

How are Alzheimer's disease and related dementias diagnosed in people with intellectual disabilities?
There is no single diagnostic test for Alzheimer's disease that can be used equally well with all adults with ID. If the presence of dementia or Alzheimer's disease is suspected, a complete physical examination and more frequent medical, neurological and psychological evaluations are strongly recommended to establish the progressive nature of the symptoms. However, universally applied screening instruments used with the general population, such as the Mini Mental Status Examination [MMSE], are generally not applicable to persons with ID because of the broad variability of innate cognitive abilities. Guidelines issued by the AAMR/IASSID (and available on these organizations' websites) offer suggested screening and evaluation procedures. As in the general population, a definitive diagnosis is only available after death. For a possible or probable diagnosis of Alzheimer's disease or other dementias, it is necessary to observe a well-documented progression of symptoms. Evaluations should be performed at select intervals using the person's previous performance as the comparison measure. Such evaluations are necessary to rule out conditions other than Alzheimer's disease, particularly reversible forms of dementia. Complete evaluations are the same as for other persons suspected of having dementia.

Generally, a general practitioner, specialist physician, neurologist, or geriatrician is a starting point for obtaining a diagnosis. Some countries have specialized centers for the evaluation and treatment of people with memory disorders, dementia, or Alzheimer's disease and these centers may provide geriatric evaluations and assessment procedures, in addition to other services. Some countries have specialized assessment services for people with ID and, in some instances, specialists on staff who can diagnose age-related problems in older people with ID.

What services are needed by individuals affected by dementia?
Studies show that persons affected by ID and dementia can continue to live in the community, if the right supports and assistance are provided. Providers can set up specialist teams that can provide advice and guidance to staff and families needing to set up specialist care services or adapt care-at-home situations. In terms of housing, since persons with ID affected by dementia may not be able to continue to live on their own, "dementia capable" housing and supports need to be provided. In addition, use of daycare (or day activity services) is recommended as it provides an atmosphere where varied and challenging activities, as well as supervision, are available. If such supportive services are in place, admission to nursing facilities or other institutions can be prevented. The types of day-to-day accommodations for adults with ID affected by dementia mirror those recommended for persons affected by dementia in the general population.

Are there underlying principles for care of people with ID and dementia?
The Edinburgh Principles, developed and issued through the IASSID, support a general belief of continued community care and a focus on the individual, use of specially designed dementia capable environments and services, and careful planning that includes adults with ID affected by dementia in generic Alzheimer's-related services and resource allocations. In essence, the Principles state that services should promote a person-centered approach, focus on individual strengths, capabilities, skills and wishes, involve the individual, her/his family and other closest supports in all phases of assessment and services planning and provision, and provide supports/services that help the person remain in his or her chosen home and community. The Principles can also be viewed and downloaded at

Resources & Publications
Developmental Disabilities and Alzheimer's Disease: What You Should Know. (The Arc, Publications Dept., The Arc of the United States, 1010 Wayne Avenue, Suite 650, Silver Spring, MD 20910 USA -

A booklet covering some of the fundamentals concerning adults with intellectual disabilities and Alzheimer's disease including what is Alzheimer's disease, its course and outcome, diagnostic suggestions, care considerations, and how to obtain assistance. Contains resource list and glossary.

What Is Dementia? - A Booklet about Dementia for Adults Who Have a Learning Disability. (Down's Syndrome Scotland, 158/160 Balgreen Road, Edinburgh, Scotland EH11 3AU)

This booklet is designed to explain dementia and its nuances to persons with intellectual disabilities (termed "learning disabilities" in Scotland). Using drawings and easy language this booklet covers many of the symptoms and behaviors classically associated with Alzheimer's disease.

Journal Articles and Books
Wilkinson, H.A., & Janicki, M.P. (2002). The Edinburgh Principles with accompanying guidelines and recommendations Journal of Intellectual Disability Research, 46, 279-284. (Blackwell-Science)

Janicki, M.P. & Dalton, A.J. (Eds.). (1999). Aging, Dementia and Intellectual Disabilities: A Handbook. Philadelphia: Taylor & Francis. (

Janicki, M.P. & Dalton, A.J. (2000). Prevalence of dementia and impact on intellectual disability services. Mental Retardation,38, 277-289. (

Janicki, M.P., Heller, T., Seltzer, G. & Hogg, J. Practice guidelines for the clinical assessment and care management of Alzheimer's disease and other dementias among adults with intellectual disability. Journal of Intellectual Disability Research, 1996, 40, 374-382. Also available from the American Association on Mental Retardation (

Resources - Internet
Dementia and intellectual disabilities-related resources and technical information are available at the University of Illinois at Chicago's RRTCADD Dementia Care

A dementia and intellectual disabilities-related Listserv is available at (topic: "Dementia/ID Listserv")

Dementia and People with Intellectual Disabilities - What Can We Do? (New York State Developmental Disabilities Planning Council, 155 Washington Avenue, Albany, New York 12222 U.S.A.-
This is an instructional video which covers the basics of how dementia affects adults with intellectual disabilities, and provides information on diagnostics and suggestions on providing supports and services in community care settings. Available in VHS and CD-Rom format, please indicate format needed.

AAMR: American Association on Mental Retardation

IASSID: International Association for the Scientific Study of Intellectual Disabilities