Down syndrome and Alzheimer's disease

People with Down syndrome are living longer than ever. That is good news. But it also means many adults with Down syndrome now reach the ages when Alzheimer's disease can begin. For them, it usually starts much earlier than in the general public, often in their early 50s.^1,2

This page explains why the risk is so high, which early signs are easy to miss, and what families and support staff can do. It is written for parents, brothers and sisters, and the many people who care for an adult with Down syndrome.

Why is the risk so high?

Down syndrome happens when a person has an extra copy of chromosome 21, a tiny bundle of genes. In about 95% of people with Down syndrome, every cell has this extra copy.¹⁰

One of the genes on chromosome 21 is called APP. It makes the protein that gets cut into amyloid (a sticky protein that builds up between brain cells in Alzheimer's). With three copies of the gene instead of two, the brain makes extra amyloid for a whole lifetime.^6,3

Because of this, experts now treat Alzheimer's in Down syndrome as close to a genetic form of the disease. The Alzheimer's Association's 2024 diagnostic criteria note that nearly all adults with Down syndrome have enough brain changes to meet the definition of Alzheimer's by their mid-40s. The pattern is much like the rare inherited forms that run in families.² You can read more about these family forms on our page about genes and dementia.

A large NIH-funded brain scan study in 2022 found that amyloid builds up in a very similar way in people with Down syndrome and in people with inherited early-onset Alzheimer's.⁶

When does it start?

Alzheimer's in Down syndrome follows a fairly predictable timeline. A study of 388 adults with Down syndrome in Spain and the United Kingdom, published in 2020, mapped it out:¹

In that study, the middle age at the early symptom stage was about 50, and the middle age at dementia diagnosis was about 54.¹ So the hidden, silent stage lasts more than 20 years.

Not every person follows this timeline. Many adults with Down syndrome have the brain changes but never show clear thinking problems.⁴ People with Down syndrome now live to about 60 on average, and some live into their 70s.³

This is much younger than typical Alzheimer's. In the general public, most people with Alzheimer's are 65 or older. See our main page on Alzheimer's disease for comparison.

Early signs to watch for

In adults with Down syndrome, the first signs are often not forgetfulness. Changes in personality, behavior and everyday skills may come first.³ Most adults with Down syndrome also do not say they are having memory trouble. A family member or staff member who knows them well usually notices first.^3,4

Watch for changes like these, compared with how the person used to be:^3,4

• Less interest in friends, talking, or favorite activities
• Shorter attention, or trouble following steps they used to manage, like a work task or a recipe
• Getting lost in familiar places
• New sadness, fear, worry or crankiness
• Being less cooperative, or new outbursts or aggression
• Restlessness or new sleep problems
• Changes in walking, balance or coordination
• Loss of skills at work, in a day program, or with self-care
• Trouble finding words, or using fewer words

As the disease moves on, a person may need more help with dressing and bathing, lose track of time and place, struggle to recognize familiar people, have bladder accidents, and develop swallowing problems.⁴ Swallowing trouble can lead to pneumonia, so it is important to tell the doctor about coughing or choking during meals.⁴ Our pages on stages of dementia and eating and swallowing explain more.

The baseline: your most useful tool

Doctors cannot judge change in someone with an intellectual disability by using the usual memory test scores. Each person starts from their own level. The key question is: has this person lost skills they used to have?

That is why experts suggest writing down the adult's usual abilities by about age 35, and putting it in their medical record.³ NDSS suggests keeping track of skills, jobs, school and work milestones, and hobbies throughout adult life.⁴

1. Write a short skills profile. What can the person do on their own? Dressing, making a snack, using a phone, taking a bus, counting money, doing a job task.
2. Note how they communicate. How many words they use, how they ask for things, favorite topics.
3. Note personality and routines. What they enjoy, how they handle change, how they usually sleep.
4. Add short videos if you can. A clip of the person talking, singing or doing a task is easy to compare later.
5. Update it every year or two, and share a copy with the doctor and any day program or group home staff.

For adults with Down syndrome, an expert group called the National Task Group on Intellectual Disabilities and Dementia Practices (NTG) made a free screening form, the NTG-EDSD. It suggests using it once a year starting at age 40. Anyone who has known the person for more than six months can fill it out. It is a screen, not a diagnosis.⁹

Our behavior diary and memory notebook can also help you track changes over time.

How Alzheimer's is diagnosed

There is no single test. The diagnosis is based on a careful doctor's judgment, using a detailed history from the people who know the person best.⁴

Step 1: Rule out other causes. Many treatable problems can look like dementia in an adult with Down syndrome. These include:^3,4

• Low thyroid
• Depression
• Hearing loss or ear infections
• Vision loss, such as cataracts
• Sleep apnea (breathing stops during sleep)
• Pain the person cannot describe

Read more in treatable conditions that look like dementia.

Step 2: See a specialist if you can. NDSS suggests a memory specialist, such as a geriatrician, neurologist, psychiatrist or neuropsychologist, ideally one who has worked with adults with intellectual disabilities.⁴ See which specialist to see.

Step 3: Compare with the baseline. The doctor will look at how much the person has changed from their own best level. Thinking tests can help, but they should never be the only measure.³

No blood test, X-ray or brain scan can confirm the diagnosis on its own.⁴ Experts also note that reading amyloid scan results may need special care in Down syndrome.²

Treatment: what is available

As of October 2026, no medicine is FDA-approved specifically for Alzheimer's in people with Down syndrome.³

• Older memory medicines. Some doctors try donepezil and similar drugs. A Cochrane review found too little evidence to say whether they help in Down syndrome.³ Limited research
• Memantine. A large international trial in adults with Down syndrome found no benefit.³ Limited research
• New anti-amyloid drugs. Lecanemab and donanemab are not a fit for now. People with Down syndrome more often have amyloid in the walls of brain blood vessels (cerebral amyloid angiopathy). For this reason, expert guidance for lecanemab says people with Down syndrome should be excluded from treatment. When that guidance was written, studies in Down syndrome were still being planned.⁷ Read about the brain swelling and bleeding risk of these drugs on our ARIA page.

Experts also urge caution with any medicine that has not been shown to be safe and helpful in this group.³ Talk with the doctor or pharmacist before starting, stopping or changing any medicine.

Good everyday care still matters. Treating hearing, vision, thyroid, sleep and pain problems can improve daily life. So can steady routines, simple step-by-step help, and staying active with familiar people and places.

Research and clinical trials

Adults with Down syndrome are now an important part of Alzheimer's research. Because the timeline is so predictable, researchers hope to test treatments years before symptoms start.¹

• The Alzheimer's Biomarker Consortium–Down Syndrome (ABC-DS) follows adults with Down syndrome over time with scans and tests. It is funded by the NIH.⁶
• The ABATE study is testing ACI-24.060, an active immunotherapy. This is a vaccine-like shot that prompts the body's own immune system to act against a disease protein. One part includes adults with Down syndrome aged 35 to 50. As of its July 2026 update, it was still recruiting.⁸

Joining a trial is a personal choice. It needs careful thought about consent, travel and the person's comfort. NDSS keeps a free guide to current trials.⁴ Our page on joining a dementia clinical trial explains what to ask.

Planning ahead as a family

Many adults with Down syndrome live with aging parents. Parents may be in their 70s or 80s when their adult child starts to show symptoms. Planning early can prevent a crisis later.

Caring for an adult child or sibling with dementia can bring deep grief, even while the person is still here. Our page on grieving someone still here and caregiver stress may help.

When to get help

See a doctor soon if an adult with Down syndrome:

• Loses skills they had before, such as at work or in self-care
• Has a clear change in personality, mood or sleep
• Has new trouble walking, or falls
• Seems confused, lost, or less able to talk

For questions and support, you can call the Alzheimer's Association 24/7 Helpline at 800-272-3900 or the National Down Syndrome Society (NDSS) Helpline at 800-221-4602 (weekdays, 9 a.m. to 5 p.m. Eastern).^3,4

Education only. This page is general information written from the sources listed. It is not medical, legal or financial advice and does not replace a doctor, therapist or lawyer who knows your situation. How we write and check pages.