For decades, Alzheimer’s disease was viewed as a condition caused by plaques, tangles, and the gradual breakdown of neurons. But a new body of research is turning that narrative on its head — pointing to the immune system as a surprising and powerful contributor to cognitive decline.

Could Alzheimer’s, in part, be the result of the brain’s immune response gone wrong?

Meet the Brain’s Immune Cells: Microglia

Inside the brain, specialized immune cells called microglia act as a cleanup crew. Their job is to clear away damaged cells, debris, and toxic proteins like beta-amyloid — one of the key hallmarks of Alzheimer’s.

Under normal conditions, microglia protect the brain. But when they become overactive or dysregulated, they can cause damage instead of preventing it.

How an Overactive Immune Response May Harm the Brain

Researchers now believe that chronic immune activation may:

• Trigger inflammation in brain tissue
• Destroy healthy neurons in an attempt to clean up protein buildup
• Disrupt communication between brain cells, impairing memory and reasoning
• Accelerate brain shrinkage, especially in regions involved in learning and recall

A 2021 study in Nature Neuroscience found that people with Alzheimer’s showed increased levels of inflammatory immune markers — even in the earliest stages of the disease.

What Triggers This Response?

While the exact causes are still under investigation, potential triggers of chronic brain inflammation include:

• Infections (such as viral or bacterial pathogens)
• Autoimmune activity
• Environmental toxins
• Stress and aging

This new understanding opens the door to novel treatment approaches — not just targeting plaques, but also calming the immune system before it causes irreversible damage.

What Can You Do to Support a Healthy Immune-Brain Connection?

While there’s no surefire way to prevent Alzheimer’s, supporting immune health may help reduce risk:

• Eat anti-inflammatory foods (e.g., leafy greens, berries, fatty fish, olive oil)
• Exercise regularly, which reduces both systemic and brain inflammation
• Get quality sleep, as sleep deprivation activates microglia
• Avoid smoking and limit alcohol, both of which disrupt immune function
• Stay socially and mentally engaged, which promotes brain resilience

Final Thoughts

The idea that Alzheimer’s may be partly driven by an overreactive immune system marks a powerful shift in how we understand — and one day may treat — this devastating condition.

Instead of simply clearing plaques after they’ve formed, the future of Alzheimer’s care may lie in identifying and addressing inflammatory triggers early, before the brain’s cleanup crew becomes a wrecking crew.