Obstructive sleep apnea (OSA) can disrupt your breathing and sleep throughout the night, which can affect your blood oxygen levels. But can OSA also affect how well your blood carries oxygen through your body?

Researchers are exploring whether OSA is connected to anemia, a condition in which the blood doesn’t have enough healthy red blood cells or hemoglobin to carry enough oxygen throughout the body.

Current research hasn’t established that one condition directly causes the other, despite their many overlapping symptoms. However, the two conditions may be connected through other health conditions.

Here’s what research says about OSA and its potential relationship with anemia.

How Sleep Apnea Affects Oxygen and Your Body

OSA happens when the muscles in the back of the throat relax, causing the tongue and other tissues to narrow or block the upper airway. When this happens, you can’t get enough air, and the oxygen level in your blood may drop.

If your brain detects that you aren’t getting enough air while sleeping, it briefly wakes you so that you can reopen your airway and breathe again. Frequent awakenings and drops in oxygen levels at night may cause daytime symptoms such as:

• Tiredness or sluggishness
• Mood or mental health changes, such as irritability or depression
• Morning headaches
• Trouble concentrating or remembering
• Dry mouth or a sore throat from mouth breathing

Over time, repeated drops in oxygen levels and poor-quality sleep may contribute to health complications, including:

• Hypertension (high blood pressure)
• Heart disease
• Type 2 diabetes
• Stroke

Overlapping Symptoms Between Anemia and Sleep Apnea

Because anemia affects how much oxygen the blood can carry, it may cause symptoms similar to those of OSA. These symptoms include:

• Tiredness
• Shortness of breath
• Weakness
• Headaches
• Irregular heartbeat
• Lightheadedness

The intensity of anemia symptoms depends partly on how severe the condition is. People with mild anemia may have few symptoms or none at all.

Symptoms can also depend on the type of anemia. For example, iron-deficiency anemia is a common type that develops when the body doesn’t have enough iron to make hemoglobin, the oxygen-carrying protein in red blood cells.

Symptoms may change depending on your diet. In the same way, daytime OSA symptoms may change depending on your breathing and sleep quality the night before.

Is There a Connection Between Sleep Apnea and Anemia?

Current research hasn’t shown that OSA directly causes anemia or that anemia causes OSA.

Although both conditions can interfere with the body’s oxygen supply and cause similar symptoms, they do so in different ways. People with OSA have periods when they can’t breathe in enough oxygen during sleep. People with anemia don’t have enough healthy red blood cells or hemoglobin to carry enough oxygen to the body’s tissues.

In fact, some evidence suggests that OSA may have the opposite effect on hemoglobin levels. One large study found that people with OSA had slightly higher hemoglobin levels, on average, than those without OSA. Researchers suggested that this difference may reflect the body’s response to repeated periods of low oxygen.

Some of the individual studies included in the analysis found lower hemoglobin levels in people with OSA. However, these results weren’t statistically significant, meaning the differences may have happened by chance.

Slightly elevated hemoglobin levels may be a sign that the body has been responding to repeated periods of low oxygen. However, more research is needed, and doctors should consider other factors when interpreting the results. Genetics and health conditions linked to inflammation, such as obesity, may also affect hemoglobin levels.

Related Conditions Linked to Anemia

Although OSA and anemia don’t appear to have a direct causal relationship, it’s possible to have both at the same time. Some conditions that commonly overlap with OSA are also associated with anemia. Two examples are chronic kidney disease (CKD) and chronic obstructive pulmonary disease (COPD).

Chronic Kidney Disease

More than one-third of people with CKD also have OSA. CKD can increase the risk of anemia, especially in its later stages. Almost half of people in the United States with stage 3a CKD have anemia, and more than 9 in 10 have it by stage 5, also known as kidney failure.

CKD is associated with anemia for several reasons. Diseased kidneys may struggle to make enough erythropoietin, a hormone that tells the body to produce red blood cells. As a result, the body may produce fewer red blood cells and carry less oxygen. People may also lose blood through frequent laboratory tests or dialysis.

People with CKD may also have low levels of iron, vitamin B12, or folate, all of which the body needs to make healthy red blood cells. Even when enough iron is available, inflammation may make it harder for the body to use it properly. Obesity, diabetes, and heart failure can also contribute to inflammation. These conditions are also associated with OSA.

Chronic Obstructive Pulmonary Disease

OSA may coexist with lung conditions such as COPD. Having both OSA and COPD is often called overlap syndrome. Up to one-third of people with COPD have anemia.

People with COPD may develop anemia for several reasons. COPD-related inflammation can interfere with the body’s ability to use iron and produce healthy red blood cells. Iron deficiency is also common among people with COPD.

One MySleepApneaTeam member wondered whether having both OSA and COPD may contribute to other health complications, including anemia. “Maybe it explains the headaches I get almost every day and night. I’m also tired all the time,” they wrote.

When To Talk to Your Doctor

If your daytime OSA symptoms are getting worse, talk to your healthcare team. They can evaluate whether your OSA needs better management or whether another condition may be contributing to how you feel.

Although anemia isn’t known to be directly caused by OSA, it may be associated with an overlapping health condition such as CKD or COPD. Ask your doctor about anemia if you have one of these conditions or symptoms that may suggest anemia. They may order blood tests to count your red blood cells and examine their size and shape.

Abnormal findings, such as too few healthy red blood cells or low hemoglobin levels, may indicate anemia. Your doctor may order additional tests to identify the cause and recommend an appropriate treatment.

Treatments for Anemia With OSA

If you have both anemia and OSA, you and your doctor can work together to manage each condition. Treatment depends on the type and cause of anemia, along with your overall health, current medications, and other health conditions. Your lifestyle may also be considered when creating your treatment plan.

Treatments for some types of anemia include:

• Iron-deficiency anemia — Treatment may involve taking iron supplements or eating more iron-rich foods. If the anemia is caused by blood loss, the source of the bleeding must also be identified and treated.
• Vitamin-deficiency anemia — Treatment may include folic acid or vitamin B12 supplements and dietary changes. People who can’t absorb vitamin B12 adequately may need injections.
• Anemia of chronic disease — Treatment focuses on managing the underlying disease. If anemia becomes severe, treatment may include a blood transfusion or erythropoietin injections to stimulate red blood cell production.

Don’t start taking iron or vitamin supplements without speaking with your healthcare provider. Too much iron or certain vitamins can be harmful, and treatment should address the specific cause of your anemia.

Join the Conversation

On MySleepApneaTeam, people share their experiences with sleep apnea, get advice, and find support from others who understand.

Have you been diagnosed with both anemia and OSA? Let others know in the comments below.