How Underlying Conditions Affect Your Immune System

Robin Berzin, MD
Medically Reviewed
March 27, 2020

While you may be familiar with—or even have—one of the conditions that make someone at higher risk of developing a severe case COVID-19 such as diabetes, asthma, and heart disease, you may be wondering, “why does someone with diabetes have an increased risk of severe respiratory illness like coronavirus?”

Chronic health conditions like those listed above impact 6 out of 10 American adults . That means the majority of us walking around, looking and feeling mostly healthy, have a chronic condition that may be compromising our underlying immunity. The physiology of that compromise can vary based on the condition, but across the board these illnesses that many of us have become accustomed to living with, can have a negative impact on our immune system —the complex network that defends our body against infections like COVID-19. If this system that protects us is impaired, it can leave us more susceptible to both contracting illnesses and more likely to experience a severe case of the illness itself.

How does diabetes and high blood sugar impact the immune system?

Diabetes is a disease that occurs when the body’s ability to produce or respond to the hormone insulin is impaired resulting in blood sugar levels that are too high, a state called hyperglycemia.

Chronic hyperglycemia—both in poorly controlled type 1 and type 2 diabetes—can affect the immune system by damaging the function of white blood cells such as neutrophils and T cells that help to fight against harmful pathogens like viruses, toxins, and bacteria. That’s likely why research has shown a greater frequency of infection in diabetics . High blood sugar also weakens the body’s antioxidant system which helps fight against free radicals and oxidative stress.

Additionally, people with uncontrolled diabetes often have reduced blood flow because high blood sugar levels create increased blood viscosity —making it hard for blood to get to all the tiny blood vessels in the eyes, heart, nerves, feet, arms, and kidneys. With reduced internal blood flow, the body is not as capable of mobilizing normal immune defenses and essential nutrients that promote the body’s ability to fight infection.

What about pre-diabetes or metabolic syndrome?

The impact on the immune system in these conditions would be similar to the above though not as severe. But with more than 100 million U.S. adults now estimated to have either diabetes or pre-diabetes and 47 million estimated to have metabolic syndrome, it is a rampant problem. Should COVID-19 be with us for a long time, we will need to—as a nation—get more serious about managing blood sugar than ever before.

How does heart disease impact the immune system?

Heart disease, which affects 121.5 million adults in the United States in some form, describes a range of conditions that affect the heart such as coronary artery disease, congenital heart defects, and issues that affect the heart’s muscle, valves, and rhythm. Most commonly , cardiovascular disease refers to conditions that arise when blood vessels become narrowed or blocked and blood can’t flow as freely—creating a risk for heart attacks or stroke. Similar to diabetes, reduced blood flow in individuals with heart disease due to narrowed blood vessels creates issues with proper circulation of immune supportive nutrients and impairs the efficient removal of toxins and waste.

In those with heart disease the immune system perceives the cholesterol-containing plaque inside coronary blood vessels as a foreign invader and works to eliminate it—spurring inflammation , the first response of the immune system to irritation. As the body continues to mount an immune defense against the coronary blockages, the prolonged state of inflammation that results puts a strain on the immune system as it’s continuously kept in an activated state. Think of this as a ‘distraction’ for the immune system—being chronically inflamed diverts the attention of your immune system, uses up its resources, and confuses our surveillance systems.

Heart disease can also impact your lung function. A damaged heart can’t effectively pump blood from your lungs to the rest of the body which can raise pressure in the pulmonary veins and push fluid into the lungs—making it harder to breathe. This connection between the heart and lungs and the strain that results between the two in advanced heart disease can set the stage for a respiratory infection, like COVID-19, to cause more harm to the body’s already weakened system.

How do chronic lung diseases like COPD, severe asthma, and fibrosis impact the immune system?

Lung conditions such as severe asthma, chronic obstructive pulmonary disease (COPD), pulmonary fibrosis, and chronic pneumonia are a group of diseases that block airflow to the lungs and make it difficult to breathe. These conditions are directly linked to the immune system because irritated lung cells in patients with the above conditions are regularly inflamed.

These inflamed lung cells are problematic because they fuel an immune system cycle in which they recruit additional inflammatory immune cells and create a chronic inflammatory environment in the lungs. Over time, ongoing lung inflammation leads to both extensive lung damage and impaired immunity to respiratory infections—making viruses such as COVID-19 that much more dangerous for these individuals.

What about immunocompromised people with cancer or those on certain medications?

Being immunocompromised means your immune system is impaired and unable to fight against pathogens. Many conditions can cause a person to be immunocompromised, including cancer treatment, bone marrow or organ transplantation, poorly controlled HIV or AIDS, and prolonged use of certain medications. Certain individuals are also born with congenital disorders that result in immunodeficiency, and elderly individuals, while by no means immunodeficient, do not respond to immune challenges as well as the young.

No matter the specific cause, immunocompromised patients produce fewer T cells, macrophages, and complement proteins, which are all key parts of the immune system. Therefore, when it comes to COVID-19, a virus that is considered highly infectious , those that are immunocompromised have little defense in place to help combat illness.

Does an autoimmune condition make you immunocompromised or at higher risk?

More than 24 million people in the United States have some sort of autoimmune condition, such as celiac disease, Hashimoto’s thyroiditis, or rheumatoid arthritis. Unlike those that are immunocompromised and have an underactive immune system, those with autoimmunity have an overactive immune system—so much so that their immune system starts attacking its own healthy cells.

While autoimmune disease is not currently identified as a higher risk population when it comes to developing a severe case of COVID-19, medical experts believe that individuals with certain autoimmune diseases, including Type 1 diabetes, lupus, rheumatoid arthritis, and multiple sclerosis, may be at increased risk of contraction of COVID-19 and of having severe complications from the disease—though research on this patient population is still needed. As far as we know as of now, not all autoimmune conditions appear to increase risk and some may not increase risk meaningfully, if at all.

When it comes to COVID-19, what might be more problematic for those with autoimmune disease is that these patients are often taking biologic medications —strong drugs that suppress the immune system in order to dampen the autoimmune response. The action of these drugs in altering the immune system may actually put these patients at higher risk of COVID-19 complications although their specific effects in regards to novel coronavirus are still widely unknown.


If you do have an underlying condition that puts you at higher risk of developing a severe case of COVID-19, the good news is that if your chronic health issues are well managed through nutrition, lifestyle, and medications, the risk of getting severely sick—from anything from the flu to COVID-19—greatly decreases.

Right now, the best way to protect ourselves is to stay calm, to stay informed, and to start—or keep —taking great care of our health.
If you’d like to learn more about COVID-19, we recommend you read some of the additional articles written by our doctors on managing coronavirus anxiety , practicing appropriate social distancing , understanding COVID-19 testing , and differentiating coronavirus from symptoms of the common cold or flu .

Robin Berzin, MD

Dr. Robin Berzin is the Founder and CEO of Parsley Health, America's leading holistic medical practice designed to help women overcome chronic conditions. She founded Parsley to address the rising tide of chronic disease in America through personalized holistic medicine that puts food, lifestyle, and proactive diagnostic testing on the prescription pad next to medications. Since founding Parsley in 2016, Dr. Berzin has seen 80% of patients improve or resolve their chronic conditions within their first year of care, demonstrating the life-changing value of making modern holistic medicine accessible to everyone, anywhere. Parsley is available online nationwide.

Dr. Berzin attended medical school at Columbia University and trained in Internal Medicine at Mount Sinai Hospital in New York City. Her book, Prescription for Happiness: How to Eat, Move, and Supplement for Peak Mental Health, was published by Simon Element in January 2022.

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