Fainting, also called syncope (pronounced SIN-ko-pee), is caused by a sudden, but temporary drop in blood pressure. The brain does not get sufficient blood flow and you lose consciousness.
Fainting can be caused by random and isolated events like low blood sugar from hunger, dehydration, or when you experience severe pain. These often are not cause for concern. Still, frequent fainting may be a red flag for a serious medical issue. For instance:
* Heart blockage: A problem with the electrical impulses that control your heart, which makes it beats too slowly and thus cannot pump enough blood to the brain.
* Heart arrhythmia: An irregular rhythm of the heart’s ventricles, the main pumping chambers, which disrupts blood flow. It often feels like a fluttering or racing heartbeat.
* Pulmonary embolism (PE): Fainting after recent air travel could be a sign of PE, a potentially fatal blockage in the lungs, according to a recent study from the American College of Chest Physicians.
Fainting also can signal a medical condition that interferes with parts of the nervous system that regulate blood pressure and heart rate, such as diabetes and malnutrition.
Other possible causes
Fainting may run in the family, according to a study in the journal Neurology. Researchers examined 44 families and found that the ones with the highest number of average fainting episodes across three generations shared a strong linkage to a specific chromosome.
Everyday situations can make people more prone to fainting, too. For instance, you may have a problem with how your body controls blood pressure when you suddenly stand from a lying or sitting position. Called orthostatic hypotension, this type of fainting is common in older people and those with poor muscle tone. Some high blood pressure medication also can contribute, as can thyroid disorders or neurological conditions, like Parkinson’s disease.
Another possible cause is vasovagal syncope. This happens when the vagus nerve–the longest of the cranial nerves, extending from the brainstem to the abdomen–is briefly stimulated and lowers both your heart rate and blood pressure. This often occurs when you strain during a bowel movement (or when urinating, for men).
This is also the main trigger of more familiar fainting incidents, such as the sight of blood, emotional distress like hearing bad news, or even laughing or coughing too hard. When this happens, it is common to feel nauseated or break out in a cold sweat before fainting.
The bottom line is that fainting is not something to take lightly. If it occurs periodically, note the symptoms and circumstances of when you fainted and seek medical advice.