Why Do We Yawn When We’re Tired?

Fact-Checked

The average person yawns five to 10 times per day (1). You started yawning while still in the womb and will continue throughout your entire life. Yawning is not exclusive to humans either. This behavior has been documented in other mammals, reptiles, birds, and fish (2).

Although yawning is most commonly associated with tiredness or boredom, there are complex physiological processes behind how and why we yawn. Other reasons for yawning may include response to ear pressure, maintaining your body’s core internal temperature, and certain diseases.

The Mechanics of Yawning

Yawning is an involuntary movement (3) during which the mouth opens and the lower jaw fully widens. Yawns begin with a deep inhalation through the nose and mouth, then end with an exhalation through the same passages. Many people stretch their arms or legs during yawns as well. The average yawn lasts five seconds.

Research suggests yawning can help you feel more awake. Your heart rate rises when the yawn reaches its peak, and this increase can continue for several seconds after you are finished yawning.

Why Do We Yawn?

Yawning usually happens due to drowsiness. Many attribute yawning to boredom, but boredom occurs when your external environment is unable to hold your attention. This disengagement with your surroundings triggers drowsiness, which in turn produces a yawn. Boredom may be the reason you yawn in certain instances, but drowsiness is still the primary cause. Other reasons for yawning may include:

Social Empathy

There is strong evidence to suggest yawning is contagious. We often feel the urge to yawn when we are in the presence of someone else who yawns, or when we view a person yawning in a movie or on television.

Experts believe contagious yawning is rooted in social empathy. Using imaging techniques, scientists have recorded responses to contagious yawning in areas of the brain that belong to a neural network associated with social behavior. Moreover, patients with disorders that limit social interaction are less likely to yawn when someone else yawns in their presence.

Brain Cooling

In recent years, researchers have explored thermoregulation (your body’s way of controlling its temperature) as another reason for yawning. Animals and humans have been observed yawning during periods of heat stress or hypothermia, which occurs in extreme cold. This has led some to speculate that yawning provides cooling when the brain’s temperature rises. One study found people are less likely to yawn during the winter (4) compared to warmer times of the year.

Ear Pressure Relief

Ear pressure is common on long flights, in elevators, and in other environments where rapid altitude changes occur. Yawning can reduce this discomfort, and may also improve hearing issues related to ear pressure. Some have proposed yawning can be a defense mechanism in response to significant altitude changes and other instances where air becomes trapped in the middle ear and cannot escape. Yawning causes the eustachian tube in the middle ear to open, releasing air in the process.

However, some have rejected this notion because yawning is not the only physiological function that causes the eustachian tube to relax. Swallowing also has a similar effect, as does the Valsalva maneuver that involves exhaling while pinching the nostrils shut and closing the mouth. More research is needed to determine whether ear pressure relief is a primary reason for yawning.

What Is Excessive Yawning?

Excessive yawning is loosely defined as yawning that occurs much more often than five to 10 times per day. The most common cause of excessive yawning is sleep debt, which affects people who habitually don’t get enough sleep (5). As the sleep you lose accumulates over time, you are more likely to feel sleepy during the day. In addition to excessive yawning, other common symptoms of long-term sleep debt include a weakened immune system, a greater risk of accidents, and memory problems.

Other reasons for excessive yawning (6) may include:

  • Vasovagal Reaction: This reaction occurs when the vagus nerve is stimulated, typically due to a heart attack or aortic dissection, which is when a tear occurs in the largest artery leading out from the heart.
  • Medical Conditions Affecting the Brain: These include a stroke, a tumor, epilepsy, or multiple sclerosis.
  • Medications: Although rare, some selective serotonin reuptake inhibitors (SSRIs) (7) can cause excessive yawning. SSRIs are normally prescribed for depression, obsessive-compulsive disorder, and other mental health disorders.
  • Thermoregulation Issues: Excessive yawning may occur when the body has trouble regulating its core temperature, but this is also rare.

Even in cases where drowsiness is the main culprit, excessive yawning may warrant attention from a physician. Contact your doctor if you do not know the reason for your excessive yawning, or if the yawning is related to feeling exceptionally tired during the day.

References

+ 7 Sources
  1. 1. Accessed on September 20, 2021.https://www.karger.com/Article/FullText/307071
  2. 2. Accessed on September 20, 2021.https://www.karger.com/Article/FullText/228262
  3. 3. Accessed on September 20, 2021.https://pubmed.ncbi.nlm.nih.gov/23776833/
  4. 4. Accessed on September 20, 2021.https://pubmed.ncbi.nlm.nih.gov/24721675/
  5. 5. Accessed on September 21, 2021.https://aasm.org/resources/pdf/pressroom/adult-sleep-duration-consensus.pdf
  6. 6. Accessed on September 20, 2021.https://medlineplus.gov/ency/article/003096.htm
  7. 7. Accessed on September 20, 2021.https://pubmed.ncbi.nlm.nih.gov/19617949/

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