But it also may decrease when a person becomes dehydrated from conditions such as diarrhea, excessive sweating, and excessive urination, which often occurs with untreated diabetes or Addison's disease. Fainting also can result when the compensatory mechanisms are affected by signals sent via the nerves from other parts of the body. For example, an intestinal cramp may send a signal to the heart via the vagus nerve that slows the heart rate enough to cause a person to faint. Such fainting is called vasomotor or vasovagal syncope. Fainting caused by urinating is particularly common in the elderly.
Swallowing syncope can accompany diseases of the esophagus.
Sometimes, anxiety leads to hyperventilation. When the carbon dioxide level decreases, the blood vessels in the brain contract, and the person may feel faint but not actually lose consciousness. Weight lifter's syncope may result from hyperventilating before lifting. In rare cases, typically in the elderly, fainting may be part of a mild stroke in which the blood flow to a part of the brain suddenly decreases. Symptoms Dizziness or light-headedness may precede fainting, especially when a person is standing.