Frequent nighttime urination, or nocturia, is defined as awakening from sleep to voluntarily urinate multiple times a night. Nocturia is a symptom of obstructive sleep apnea but is usually misdiagnosed as being related to prostate and bladder problems as well as being older in age.
During an episode of sleep apnea, the airways become obstructed causing the oxygen to decrease and the carbon dioxide to increase, causing the blood acid levels to raise, heart rate to decrease and the lungs to constrict. The combination of these symptoms alerts the body that something is wrong, causing the heart to beat rapidly.
These events signal to the body a false sense of fluid overload. The heart then begins to excrete a protein that signals the body to release fluid, causing the person to wake with the urge to urinate. In severe cases, a person with nocturia may be awakened to urinate five to six times during the night.