Nocturia, or nocturnal urination, is sometimes a symptom of sleep apnea. In fact, nocturia among younger individuals--who are less likely to have other medical causes of nocturia--is a strong indicator of sleep apnea. While the precise relationship has not been thoroughly studied, it appears that the most likely reason patients with untreated sleep apnea have more frequent urination at night is related to the increased pressure in the right side of the heart. This increased pressure is usually the result of low oxygen levels in the bloodstream caused by the apnea events: when oxygen levels fall, the heart works harder to get oxygen to the brain.
An increased pressure in the heart is a sign that there is too much liquid in the body: when the heart receives the stimulus of the increased pressure, higher levels of a hormone called atrial natriuretic peptide (ANP) are secreted. ANP is a diuretic that is associated with the increased need to urinate.
When sleep apnea is effectively treated, nighttime urination is also reduced. Studies have shown that ANP levels in patients with untreated sleep apnea are increased and levels reduced in patients using CPAP effectively. Remember, not all causes of frequent urination are related to untreated sleep apnea; prostrate problems, for example, may cause increased need for urination. Discuss any concerns you may have with your doctor.
Patrick J. Strollo, Jr., MD is the Medical Director of the Pulmonary Sleep Evaluation Laboratory at the University of Pittsburgh Medical School.
Return to Top
