Introduction
Adults with Down syndrome are at an increased risk of developing Alzheimer's disease as they age. However, Alzheimer's is not inevitable. There are many other potential conditions to consider when memory-related concerns arise, making a careful and systematic approach to diagnosis essential.
The Relationship Between Alzheimer's Disease and Down Syndrome
The full or partial third copy of chromosome 21 plays a pivotal role in this relationship, as it carries a gene that produces one of the key proteins involved in the brain changes associated with Alzheimer's disease. In addition, scientists have identified numerous genes on chromosome 21 that contribute to the ageing process and increase the risk of developing Alzheimer's. This unique characteristic of chromosome 21 is what makes Alzheimer's disease a greater concern for individuals with Down syndrome compared to those with other forms of intellectual disability.
Overview
Alzheimer's disease is a form of dementia that progressively destroys brain cells, affecting memory, learning, reasoning, communication, and the ability to carry out basic daily activities. It is not an inevitable outcome for people with Down syndrome. While all individuals with Down syndrome carry an elevated risk, many do not develop any Alzheimer's-related changes during their lifetime.
The risk roughly doubles with each decade of age, but never approaches 100% at any stage. It is therefore particularly important to exercise caution and consider all potential alternative causes of age-related changes before arriving at a diagnosis. Estimates suggest that Alzheimer's disease affects approximately 30% of individuals with Down syndrome after the age of 50, rising to close to 50% after age 60.
Stages of Alzheimer's Disease
Alzheimer's disease progresses through three stages: early, middle, and late.
Early Stage
- Short-term memory loss: difficulty recalling recent events, learning new information, remembering names, and keeping track of the day and date; asking the same questions or telling the same story repeatedly.
- Difficulty acquiring and retaining new information.
- Changes in expressive language: difficulty finding words, reduced vocabulary, shorter sentences, and less spontaneous speech.
- Changes in receptive language: difficulty understanding spoken language and verbal instructions.
- Declining ability to plan and sequence familiar tasks.
- Changes in behaviour and personality.
- Disorientation: difficulty navigating familiar environments.
- Deteriorating fine motor skills.
- Reduced productivity at work.
- Difficulty completing complex, multi-step tasks, including household chores.
- Depressed mood.
Middle Stage
- Declining ability to perform daily tasks and self-care activities.
- Further deterioration of short-term memory, while long-term memory is generally preserved.
- Reduced ability to identify time and place.
- Continued decline in language expression and comprehension: increasingly limited vocabulary, communication reduced to short phrases or single words.
- Difficulty recognising familiar people and objects.
- Impaired judgement and reduced attention to personal safety.
- Mood and behavioural changes: anxiety, hallucinations, sleep disturbances, and confusion.
- Physical changes: new-onset seizures, urinary and possibly faecal incontinence, swallowing difficulties, and motor changes including difficulty walking and reduced depth perception.
Late Stage
- Severe impairment of both short- and long-term memory; loss of ability to recognise family members and familiar faces.
- Full dependence on others for all personal care: bathing, dressing, toileting, and eventually eating.
- Progressive loss of mobility, ultimately requiring a wheelchair or remaining bed-bound.
- Near-total loss of speech, reduced to minimal words or sounds.
- Loss of the mechanical ability to chew and swallow, leading to respiratory complications and pneumonia.
- Complete urinary and faecal incontinence.
Identifying and Diagnosing Alzheimer's Disease
Establishing a Baseline
Most adults with Down syndrome will not self-report concerns about their memory. Instead, identifying early changes requires a skilled healthcare professional who knows the individual well. Suspicion of Alzheimer's disease arises when a person shows one or more changes compared to their previous level of functioning.
To monitor change effectively, one must know what the individual was capable of when they were well — this is referred to as their personal "baseline". Formal monitoring of memory-related functions should be a priority during mid-to-late adulthood.
Alzheimer's disease is a clinical diagnosis, made at the physician's discretion. No single blood test, X-ray, or scan is sufficient to diagnose or confirm it. Diagnosis relies heavily on an accurate history documenting the gradual loss of memory and functional ability. It is essential to remind caregivers to provide a detailed symptom history, and the specialist must carefully weigh all factors before reaching a considered diagnosis. Many conditions common in ageing adults with Down syndrome — including hearing loss, visual impairment, hypothyroidism, and obstructive sleep apnoea — can closely mimic or be confused with dementia.
Obtaining a Memory Assessment
A memory assessment should be conducted by a qualified specialist, such as a geriatrician, neurologist, psychiatrist, or neuropsychiatrist. It is preferable that this specialist has experience evaluating individuals with intellectual disabilities.
Assessments should be comprehensive and appropriately calibrated to each patient's baseline level of intellectual disability. A thorough evaluation must take into account all other potential contributing factors — medical, psychological, environmental, and social — that may be causing or contributing to the reported changes.
Source: Information in this section has been reproduced under an exclusive agreement with the National Down Syndrome Society (NDSS). Available at: www.ndss.org