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The Link Between Alzheimer’s, Inflammation, and Oxidative Stress

Medically Reviewed by Carol DerSarkissian, MD on August 03, 2022

Researchers aren’t sure exactly what causes Alzheimer’s, but they do know that it’s linked to a buildup of protein clumps and knotted clusters of molecules in the brain. Called beta-amyloid plaques and tau tangles, these are two telltale changes in the brain associated with Alzheimer’s disease.

Now scientists increasingly suspect that Alzheimer’s may also be linked to two other risk factors that affect everyone: oxidative stress and inflammation.

How Alzheimer’s Happens

The disease unfolds slowly. Changes in the brain might start 10 years before you notice the first symptoms of Alzheimer’s-related dementia, which interferes with your ability to think, reason, and remember. Scientists think that the clumps of protein make it difficult for brain cells to talk to each other. Over time, the brain cells die off.

We know that certain things raise your chances for Alzheimer’s disease. They include:

Some of those risk factors are driven by oxidative stress and inflammation, which are natural processes in our bodies.

Oxidative Stress

This is when your body has too many damaging molecules called free radicals. Your cells make free radicals, which are healthy in low amounts. You can also get exposed to them from outside sources like cigarette smoke and air pollution.

Antioxidants in your body destroy free radicals before they can damage and age your cells. But if free radicals outnumber your antioxidants, it results in oxidative stress. In turn, that stress may lead to Alzheimer’s as well as a host of other diseases such as Parkinson’s, multiple sclerosis, cancer, cardiovascular disease, and diabetes.

Beta-amyloid, the protein that builds up in the brains of many people who are found to have had Alzheimer’s, is a type of antioxidant.

But oxidative stress might cause your cells to make a faulty version of beta-amyloid that forms harmful plaques. As you age, it becomes harder for your body to break down these misfolded proteins. At the same time, the plaques might spur your body to make more free radicals, triggering a vicious cycle of oxidative stress and plaque buildup.

Inflammation

This is your body’s protective response to infection. But germs and viruses aren’t the only invaders that can trigger inflammation. So can a poor diet, smoking, stress, and even your own immune system if it goes haywire.

But chronic, or long-term, inflammation can damage healthy brain cells. This is what happens in Alzheimer’s. Inflammation in the brain can worsen amyloid plaques and tau tangles and lead to dementia. Certain genes and exposure to cigarette smoke, air pollution, and other chemicals can raise your risk for inflammation in the brain.

What You Can Do About Oxidative Stress and Inflammation

Don’t smoke. The toxins in cigarette smoke are packed with free radicals. Smoking also raises your risk for other problems associated with dementia, like heart disease and diabetes. Avoiding or quitting smoking can lower your risk for Alzheimer’s.

Limit alcohol. Some studies have suggested that moderate drinking protects you against Alzheimer’s. But, heavy drinking is linked to faster brain aging and a higher risk for dementia. Alcohol is a toxin and causes inflammation in the brain. Moderate drinking is one drink (usually a single can of beer or glass of wine) a day for women or two drinks a day for men.

Eat a healthy diet. You can fight oxidative stress and inflammation by eating more fruits and vegetables, which often contain antioxidants. Vitamins C and E are two common antioxidants. Oily fish like salmon, leafy greens, and olive oil have anti-inflammatory effects. Avoid fried and processed foods.

But you can’t just eat your way to good health. It takes a whole healthy lifestyle to help keep diseases away. Antioxidant supplements haven’t been shown to prevent age-related diseases like Alzheimer’s. Taking too many might even be harmful, because a healthy body needs a small amount of free radicals.

Try probiotics. Some scientists think that oxidative stress and inflammation in the brain might be linked to the health of your gut bacteria. People with Alzheimer’s disease tend to have fewer inflammation-fighting bacteria and more inflammation-causing bacteria than similar people do. Studies suggest, but don’t prove, that probiotics, which contain helpful live bacteria, might help with some cognitive symptoms of Alzheimer’s. Yogurt, kimchi, fresh sour dill pickles, and aged cheese are some foods that contain probiotics.

Exercise. Working out moderately helps your body to make more antioxidants. Regular exercise can significantly lower your chances for getting Alzheimer’s. Aim for three to five exercise sessions (20-30 minutes each) per week. Day-to-day activities like gardening or brisk walking count as exercise. Don’t push yourself too hard: overtraining can cause your muscles to release free radicals.

Keep a healthy weight. Obesity (a BMI of at least 30) might promote inflammation throughout your body, including the brain. As a result, people who are overweight or obese are more likely to get dementia, including Alzheimer’s disease.

Minimize stress. Mental and physical stress lead to inflammation and oxidative stress. Over time, it can raise your chances for getting Alzheimer’s and other neurodegenerative disorders. Journaling, yoga, deep breathing exercises, or meditation can help keep your stress in check.

Get enough sleep. Sleep helps your brain to clear out beta-amyloid plaques. Poor sleep is linked with having more plaques, which in turn affects how your brain stores memories. As a result, sleep problems like insomnia can cause inflammation in your brain and raise your chances for getting Alzheimer’s disease. Get a good night’s sleep by following a regular sleep schedule, exercising often, and letting in bright light in your room in the morning.

Show Sources

SOURCES:

Alzheimer’s & Dementia: “Inflammation as a central mechanism in Alzheimer’s disease.”

Alzheimer’s Society: “Physical exercise and dementia,” “Sleep and dementia risk,” “Smoking and dementia.”

Aging: “Efficacy of probiotics on cognition, and biomarkers of inflammation and oxidative stress in adults with Alzheimer’s disease or mild cognitive impairment — a meta-analysis of randomized controlled trials.”

Cleveland Clinic: “Alzheimer’s Disease,” “Inflammation.”

Frontiers in Behavioral Neuroscience: “Alcohol-Induced Neuroinflammatory Response and Mitochondrial Dysfunction on Aging and Alzheimer’s Disease.”

Frontiers in Physiology: “Lifestyle, Oxidative Stress, and Antioxidants: Back and Forth in the Pathophysiology of Chronic Diseases.”

International Journal of Epidemiology: “Higher risk of dementia in English older individuals who are overweight or obese.”

Journal of Alzheimer’s Disease: “Association of Stress with Risk of Dementia and Mild Cognitive Impairment: A Systematic Review and Meta-Analysis.”

Journal of Personalized Medicine: “Obesity and Diabetes Mediated Chronic Inflammation: A Potential Biomarker in Alzheimer’s Disease.”

The Lancet Neurology: “Implications of sleep disturbance and inflammation for Alzheimer's disease dementia.”

Neurobiology of Stress: “Chronic stress as a risk factor for Alzheimer's disease: Roles of microglia-mediated synaptic remodeling, inflammation, and oxidative stress.”

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