Amyloidosis happens when abnormal proteins build up in different parts of the body. These clumps, called amyloid deposits, can damage organs — and, in severe cases, cause organ failure.

You may have also heard about amyloid deposits linked to Alzheimer’s disease, the most common form of dementia. In Alzheimer’s, these deposits collect in the brain and form what are called amyloid plaques, which some scientists believe may be part of what causes damage in the brain that leads to dementia.

Given this connection, you might wonder if systemic amyloidosis — the type that affects many organs — can also lead to dementia. While there’s no evidence that systemic amyloidosis causes dementia, the buildup of amyloid proteins in the brain is a hallmark of Alzheimer’s disease.

To better understand this relationship, it helps to know about the different types of amyloid deposits and where they show up. This article breaks down what’s known about amyloidosis and dementia and how these conditions may be connected.

What Is Amyloidosis?

Amyloidosis is a rare disease that occurs when certain proteins misfold and stick together, forming clumps called amyloid deposits. These deposits can build up in different organs and tissues, where they interfere with functioning. Over time, they may cause serious damage.

There are several types of amyloidosis, and each type can affect different organs. The condition may involve a single organ or multiple ones. Commonly affected organs include the:

• Kidneys
• Heart
• Liver
• Spleen
• Stomach or intestines
• Nervous system (including the brain, spinal cord, and nerves)

Amyloidosis affects people differently, depending on which organs are involved. Common early symptoms may include:

• Irregular heartbeat
• Diarrhea and constipation
• Severe fatigue (extreme tiredness that doesn’t improve with rest)
• Shortness of breath
• Unintended weight loss

Because the symptoms vary from person to person and can also resemble those of other conditions, amyloidosis can be hard to diagnose.

Can Amyloidosis Affect the Brain?

Systemic amyloidosis has not been shown to directly cause typical forms of dementia. However, a brain-specific condition called cerebral amyloid angiopathy (CAA) involves amyloid buildup in the brain’s blood vessels.

In CAA, these protein deposits can weaken the blood vessel walls and make them more likely to bleed. This bleeding can be minimal and go unnoticed, or it can be significant and lead to sudden confusion, strokelike symptoms, and cognition problems (trouble with thinking and memory).

CAA is a leading cause of hemorrhagic stroke (brain bleeding) and cognitive decline in older adults. However, it’s not the most common cause of overall cognitive decline — that’s usually the result of Alzheimer’s disease and other dementias.

What Is Dementia?

“Dementia” is a broad term that describes several conditions that affect how the brain works. It includes many different diseases, including Alzheimer’s. Dementia causes problems with memory, thinking, and decision-making, and it can eventually interfere with daily life.

Unlike amyloidosis, dementia mostly affects the brain and not other organs. Early signs of dementia include problems with short-term memory or everyday tasks, such as paying bills, cooking, and remembering appointments. Dementia is progressive — it gets worse over time. In some cases, symptoms progress quickly.

What Causes Amyloidosis and Dementia?

Both amyloidosis and dementia involve deposits of amyloid protein, but the reasons for the buildup appear to be different.

Amyloidosis Causes

Researchers have a basic understanding of some of the causes of amyloidosis, which vary depending on the type. Some forms are hereditary (passed down in families). Risk factors for amyloidosis include:

• Being older than 50
• Having an inflammatory disease
• Experiencing chronic infections
• Having a family history of amyloidosis
• Living with multiple myeloma (a type of blood and bone marrow cancer)
• Receiving dialysis (machine-assisted blood-filtering) for kidney disease for over five years

Dementia Causes

Dementia happens when neurons (nerve cells in the brain) are damaged and no longer work properly. Lesions (scarring) from the damage disrupt how brain regions communicate. For example, when brain cells in the area that handles memories are affected, memory loss may result.

Deposits of amyloid proteins are a key feature of Alzheimer’s. Some studies have found that as amyloid builds up in the brain, memory and thinking skills tend to decline. But scientists still don’t know whether amyloid buildup causes Alzheimer’s or is just one part of the disease process.

The Amyloid Hypothesis

For more than 40 years, the amyloid hypothesis has been the primary theory to explain Alzheimer’s disease. This idea suggests that the buildup of beta-amyloid — small fragments of amyloid proteins — is the main cause of Alzheimer’s. These beta-amyloid clumps may disrupt communication between brain cells and cause brain cells to die.

To test this hypothesis, researchers have studied the use of anti-amyloid antibodies — immune proteins that fight against beta-amyloid proteins — to prevent buildup. In 2016, a clinical trial found that this approach reduced beta-amyloids in the brain and slowed the rate of cognitive decline in people with mild or preclinical (early) Alzheimer’s disease.

The U.S. Food and Drug Administration (FDA) has approved two anti-amyloid medications, lecanemab and donanemab, to treat early-stage Alzheimer’s. These targeted therapies are designed to gradually remove amyloid plaques from the brain. The treatments are used in people with mild symptoms who have been confirmed to have amyloid beta plaques in their brains.

Even with these advances, scientists don’t fully understand the causes of Alzheimer’s disease. Researchers continue to explore the amyloid hypothesis, and some recent findings question the relationship between amyloid buildup and Alzheimer’s.

The Connection Between Amyloidosis and Dementia

Both amyloidosis and dementia involve an abnormal buildup of amyloid proteins, but they affect different parts of the body. In amyloidosis, the protein deposits form in organs such as the kidneys, heart, or liver. In Alzheimer’s, the buildup occurs in the brain.

In amyloidosis, amyloid buildup can cause organ damage. In dementia, scientists are focusing on how two proteins — beta-amyloid and tau proteins — form plaques and tangles, which may play a role in damaging brain cells.

Age is another link between these conditions. Amyloidosis is more likely to develop over age 50. Similarly, the risk of dementia and Alzheimer’s disease increases with age.

Ways To Support Brain Health if You’re Living With Amyloidosis

There’s no clear evidence that systemic amyloidosis directly raises the risk of dementia. Still, it’s important to care for your brain and strengthen your immune system throughout life — which is true for everyone. In one study, people who practiced four or five healthy lifestyle habits had a 60 percent lower risk of Alzheimer’s compared to those who followed none or just one. These healthy habits included:

• Eating a healthy diet
• Getting regular moderate to vigorous exercise
• Not smoking
• Drinking alcohol in light to moderate amounts
• Staying mentally active (such as working puzzles, reading, or learning new skills)

While there’s still much to learn about the connection between amyloidosis and dementia, taking steps to protect your brain and overall health can make a meaningful difference at any age.

Talk With Others Who Understand

MyAmyloidosisTeam is the social network for people with amyloidosis and their loved ones. On MyAmyloidosisTeam, members come together to ask questions, give advice, and share their stories with others who understand life with amyloidosis.

Are you living with amyloidosis? Share your experience in the comments below, or start a conversation by posting on your Activities page.