Dementia Plaque, Tangles Often Develop Early in People with Down Syndrome
My friend Sondra sent me a story recently about the association between Down syndrome and Alzheimer’s disease. Her son has Down syndrome and Sondra is very active in advocacy groups for people who have this condition. Therefore, she wanted to share this research with me because she felt others would find this information helpful.
The new study involves 19 people who had Down syndrome who did not have dementia. Their average age was 36 years old. Ten people who have been diagnosed with Alzheimer’s disease (but not Down syndrome) and who were, on average, 66 years old also participated, as did 10 people who did not have Alzheimer’s or Down syndrome. This last group has an average age of 43 years.
The researchers used positron emission tomography (PET) scan to look at whether amyloid plaques and tau tangles had developed in the participants’ brains. These plaques and tangles are hallmarks of Alzheimer’s disease and have been seen previously in autopsies of people with Down syndrome. These plaques and tangles keep the brain’s neurons from functioning properly.
The PET scans indicated that the study participants who had Down syndrome had high levels of the amyloid plaque and tau tangles. Furthermore, these indicators were similar to the study participants who had been diagnosed with Alzheimer’s disease. The scans also showed that the participants who had Down syndrome had much higher levels of the tangles and plaques than members of the control group who did not have either Down syndrome or Alzheimer’s disease.
Interestingly, the researchers found that the highest levels of tau and amyloid were in the brain’s parietal and frontal regions. The parietal lobe is responsible for cognition, information processing, pain sensation, touch sensation, speech, visual perception and spatial orientation (having a sense of direction while moving around in an environment). The frontal lobe is responsible for reasoning, motor skills, higher level understanding as well as expressive language. This part of the brain receives transmissions from other areas of the brain and then uses the information to determine the body’s movements.
The researchers also noted that age is associated with brain changes in the participants with Down syndrome. A large number of these participants who were older than 45 years of age exhibited the cognitive and behavioral symptoms that are often seen in dementia
Previous studies involving the brains of people who have Down syndrome who have died have found that plaques may be initially detected in adolescence; however, the tau tangles appear later as the person ages. The development of the tangles is what causes Alzheimer’s-like symptoms despite the early presence of the plaques.
The Alzheimer’s Association points out that people who have Down syndrome are more likely to develop younger-onset Alzheimer’s disease; because they live a much shorter life (on average, 55-60 years).
Early symptoms of Alzheimer’s in people with Down syndrome can include changes in overall function, personality and behavior (as opposed to memory loss and forgetfulness). These specific symptoms are:
- A decreasing interest in being sociable, having conversations or expressing thoughts;
- Less enthusiasm for usual activities;
- A decline in the ability to pay attention;
- Feelings of sadness, fearfulness or anxiety;
- Sleep disturbances;
- Seizures as an adult;
- Changes in coordination;
- Changes in ability to walk;
- Increased noisiness; and
- Increased excitability.
The Alzheimer’s Association points out that diagnosing someone with Down syndrome with Alzheimer’s can be difficult because of the challenge in assessing change sin thinking skills in someone who has an intellectual disability. Therefore, experts recommend:
- Documenting the person’s baseline intellectual, social and behavioral function by age 35.
- Look for changes in the person’s day-to-day function. These changes can be the early signs of a decline in thinking skills.
- A professional assessment by a dementia expert may be helpful. However, cognitive tests shouldn’t be the only benchmark used to diagnose Alzheimer’s in a person who has Down syndrome.
- Professionals should rule out other reasons for symptoms. These other reasons could include thyroid problems, depression, chronic ear infections, chronic sinus infections and sleep apnea.
Primary Sources for This Sharepost:
Alzheimer’s Association. (nd). Down syndrome and Alzheimer’s disease.
Nelson, L. D., et al. (2013). Positron emission tomography of brain β-amyloid and tau levels in adults with Down syndrome. JAMA Neurology.
Williams, S. C. P. (2013). ScienceShot: ‘Alzheimer’s’ in the Down syndrome brain.