Lightheadedness, nausea, ringing ears, blurred vision. Suddenly you lose consciousness and wake up on the ground. These are your “mayday” signals when vasovagal syncope attacks.

Vasovagal syncope, also known as vasodepressor syncope, is the most common cause of fainting. It can be triggered by various situations, including dehydration, extreme heat or standing for long periods of time. Emotional triggers such as seeing blood, feeling stressed or being in pain can cause vasovagal syncope too. These triggers can activate involuntary (autonomic) reflex responses that slow your heart rate and widen your blood vessels. As a result, your blood pressure drops suddenly, leading to less blood flow and oxygen to your brain, and causing fainting. “Syncope” is the scientific word for fainting.

The cause of vasovagal syncope has been a longstanding mystery. Some suggest it could be due to an exaggerated autonomic response to certain triggers. Others think that it is a disease and that some people are more likely than others to experience it due to genetics. While the mechanism of vasovagal syncope remains unclear, the vagus nerve is known to play an integral part in generating this reflex by regulating cardiovascular function.

Anyone can experience vasovagal syncope at any age. Children and young adults younger than 40 are most likely to have it. In older adults, vasovagal syncope accounts for more than 50% of fainting cases. Interestingly, people with autonomic nervous system dysfunction have a lower risk of experiencing vasovagal syncope.

While vasovagal syncope itself—your body’s autonomic responses being triggered—is not dangerous, fainting episodes can be hazardous because you can hurt yourself when you fall. Recognizing the symptoms and knowing how to manage them are important to help keep yourself safe. In most cases, you’ll notice pre-fainting symptoms, or the mayday signals, I mentioned earlier before a syncope episode. You might also experience heart palpitations or feel sweaty or weak before you faint.  

To make a vasovagal syncope episode less severe or less likely to happen, try to avoid your triggers. Staying hydrated and moving slowly when you change body positions can help too. When the mayday signals come, doctors often advise people to lie down on their back until the symptoms pass to prevent a fainting episode. In severe cases, your doctor might recommend a heart pacemaker to regulate your cardiovascular responses. It’s best to see a doctor when you experience frequent fainting episodes. Your doctor can help you become familiar with the mayday signals and your triggers so you’ll be ready to launch your management plan for the next syncope attack.