Individuals with OSA often experience both nighttime and daytime symptoms. Nighttime symptoms include loud snoring, gasping for breath, and apneic episodes (often witnessed by a bed partner). Daytime symptoms can involve excessive sleepiness, especially with impairment of driving, feeling unrefreshed upon morning awakening, dry throat, poor concentration, morning headaches, and erectile dysfunction in men.
OSA initiates a chain of events that stresses the cardiovascular system and increases the risk of hypertension, cardiac arrhythmias, stroke, and premature death. Basically, the combination of disturbed sleep and oxygen starvation creates stress on the body. The hypoxemia associated with sleep apnea triggers the sympathetic nervous system to release stress hormones, including adrenaline, which causes an increased heart rate and BP. In response to high BP, the heart secretes atrial natriuretic factor, a hormone that acts on the kidneys to increase urine output and lower BP. This phenomenon leads to another OSA symptom: frequent nighttime urination (nocturia).
OSA affects more than sleep and the cardiovascular system. Repetitive arousals prevent the body from entering the deep stage of sleep during which growth hormone is released. Growth hormone, in addition to increasing height in children and adolescents, helps keep muscles and bones strong, maintains blood glucose, stimulates the immune system, and reduces body fat. Sleep apnea may also lead to mood changes and exacerbate disorders such as anxiety and depression.
Untreated OSA is associated with a number of chronic conditions, including obesity and diabetes, which both predispose patients to OSA and are exacerbated by it. Obesity is the main risk factor for OSA. Sleep deprivation leads to higher levels of the hormone ghrelin, which causes an increased appetite, and lower levels of the hormone leptin, which tells the body it's full and to stop eating. This imbalance leads to overeating and weight gain.
When sleep apnea leads to excessive daytime sleepiness, beginning and sustaining an exercise program becomes increasingly unlikely. Accordingly, treatment of sleep apnea is an important aspect of weight control that can enable the patient to act on his or her motivation to embark on and maintain an effective weight loss program. It's generally agreed that as little as a 10% decrease in weight can lead to significant improvements in sleep apnea symptoms.