Hypertension and OSA

There are many comorbid medical conditions associated with unmanaged obstructive sleep apnea (OSA) the most common of which is hypertension. The most recent research indicates that thirty to fifty percent of those who have essential hypertension have OSA. Individuals with drug-resistant hypertension are even more likely (eighty percent) to have OSA.

The pathophysiology of this relationship involves two primary pathways. Simply stated when oxygen levels in the blood drop abnormally due to obstructed breathing there is a decrease in available oxygen to produce nitric oxide in the body. No air breathed in on inspiration means no oxygen. An important function of nitric oxide is vasodilation of the blood vessels. Without sufficient amounts of nitric oxide in the blood, the vessels constrict which can result in hypertension. 

A second pathway to hypertension-related to OSA involves the “fight or flight” syndrome or sympathetic activation that occurs with every breathing obstruction during sleep. The sympathetic response in the body to each obstruction is an elevation in blood pressure, heart rate, and respiration rate. The repetitive collapse of the airway numerous times per hour throughout the night does not allow the blood pressure to reset to the usual level. During sleep blood pressure is known to drop ie “dip” about ten percent of the normal daytime level. Apneics are termed “non-dippers” as their blood pressure is repeatedly elevating and essentially remains at a higher level upon awakening and throughout the day.

Prevalence and associated factors of obstructive sleep apnea in patients with resistant hypertension. Am J Hypertens. 2014 Aug;27(8):1069-78. Muxfeldt, Margallo Guimarães,Salles

Association of sleep-disordered breathing, sleep apnea, and hypertension in a large community-based study. Sleep Heart Health Study. JAMA. 2000 Apr 12;283(14):1829-36;Nieto FJ1, Young TB, Lind BK, Shahar E, Samet JM, Redline S, D'Agostino RB, Newman AB, Lebowitz MD, Pickering TG.