Memory Digest

Inflammation and the Brain

Inflammation, the body's defense response, appears to play a real role in Alzheimer's disease; learn what microglia do, what the research shows about midlife inflammation, and what you can and can't do about it.

Last reviewed: October 2026

Inflammation is the body's way of fighting infection and repairing injury. A swollen, red cut is inflammation doing its job. But when inflammation goes on too long, it can harm healthy tissue. Over the past 15 years, researchers have become convinced that inflammation is an important part of the Alzheimer's story, not just a side effect.

The brain's immune cells

The brain has its own immune cells called microglia. Normally they act like a cleanup crew, clearing away debris, dead cells and proteins such as amyloid. Other support cells called astrocytes help too.

In Alzheimer's disease, microglia gather around amyloid plaques. At first, this may help. Over time, though, they can get stuck in an "always on" state, releasing inflammatory chemicals that may damage nerve cells and the connections between them. A major 2015 review in Lancet Neurology, led by Michael Heneka, concluded that this inflammation is not just a reaction to the disease, but likely contributes to how it develops and worsens.

The National Institute on Aging lists chronic inflammation among the processes scientists believe are involved in Alzheimer's, along with amyloid, tau and blood vessel problems. See Amyloid and Tau Explained and Alzheimer's Disease for the bigger picture.

Clues from genetics

Some of the strongest evidence comes from genes. Large genetic studies have found that many genes linked to Alzheimer's risk are active in microglia. One example is TREM2: rare changes in this gene, which affects how microglia respond to damage, raise Alzheimer's risk substantially. This suggests the immune response itself helps decide who gets the disease.

Inflammation in the body, not just the brain

Inflammation elsewhere in the body may also affect the brain.

The ARIC study. Researchers measured inflammation markers in the blood of more than 12,000 middle-aged Americans and followed their thinking skills for 20 years. People with higher inflammation in midlife had somewhat faster decline in memory and thinking over the following two decades, even after accounting for other health factors. The effect was modest, and an observational study like this can't prove that inflammation caused the decline.

Long-lasting inflammation in the body is linked to:

• Obesity, especially belly fat
• Type 2 diabetes
• Smoking
• Gum disease
• Chronic infections
• Inactivity and poor sleep
• Some autoimmune conditions

Many of these are also known dementia risk factors.

Do anti-inflammatory drugs help?

Not so far. Years ago, studies noticed that people who regularly took anti-inflammatory painkillers (NSAIDs, such as ibuprofen or naproxen) seemed to get Alzheimer's less often. But when these drugs were tested in proper clinical trials, they did not prevent or slow Alzheimer's, and they carry risks such as stomach bleeding, kidney problems and heart problems. Don't start taking them for brain health.

Researchers are now testing more targeted approaches, such as drugs that change how microglia behave. These are still experimental. See Dementia Research Today and Joining a Clinical Trial.

Infections and inflammation

Some scientists think certain infections, like herpes viruses, may trigger inflammation and amyloid buildup in the brain. Interestingly, studies suggest the shingles vaccine may lower dementia risk. This is an active area of research. See Vaccines, Infections and Dementia Risk.

What you can do

There's no proven "anti-inflammatory diet" or supplement for preventing dementia. But habits that lower chronic inflammation are also good for the heart and brain:

• Move every day. Regular exercise lowers inflammation markers. See Exercise and the Brain.
• Eat a pattern rich in vegetables, fruit, whole grains, beans, nuts, olive oil and fish, such as the MIND diet.
• Keep a healthy weight and manage blood sugar.
• Don't smoke. See Smoking and Dementia.
• Sleep well. See Sleep for Brain Health.
• Care for your teeth and gums, and see a dentist regularly.
• Stay up to date on vaccines your doctor recommends.
• Treat chronic conditions such as diabetes or autoimmune disease with your doctor.

Be wary of supplements sold as brain "anti-inflammatories." See Supplements and Memory Claims.

The bottom line

Inflammation is now seen as a real player in Alzheimer's disease, especially through the brain's immune cells. No anti-inflammatory drug has yet been proven to prevent or treat it, but healthy habits that calm inflammation in the body are worthwhile for many reasons.

This article is for general information and is not a substitute for advice from your own doctor.

Sources

1. Heneka MT et al. Neuroinflammation in Alzheimer's disease. Lancet Neurology, 2015
2. Walker KA et al. Systemic inflammation during midlife and cognitive change over 20 years: The ARIC Study. Neurology, 2019
3. National Institute on Aging: What Causes Alzheimer's Disease?

Not medical advice. This article is general information, not a diagnosis or treatment plan for any individual. Talk with a doctor about your situation.

Related articles

• Amyloid and Tau Explained
• Dementia Research Today
• Vaccines, Infections and Dementia Risk
• Alzheimer's Disease
• Diabetes and Dementia