Obstructive Sleep Apnea Syndrome and Diabetes-Related Eye Disease
Common disorder linked to heart disease, other vision complications.
By A.Paul Chous, MA, OD, FAAO
Obstructive Sleep Apnea Syndrome (OSAS) is a disorder of the upper respiratory system caused by blockage of the passage connecting the nose to the windpipe. It is a very common condition in patients who are overweight or obese, including many patients with diabetes.
Symptoms of sleep apnea include:
- momentary stoppage of breathing while sleeping (up to several hundred times a night),
- anytime sleepiness,
- generalized fatigue.
It is often a person's sleeping partner who notices a pattern of discontinued breathing and, amazingly, patients are typically totally unaware that this is happening. For several years now, we have known that OSAS increases the risk of stroke. More recently, OSAS has been linked to heart disease and increased risk of several eye diseases, including diabetic retinopathy, glaucoma and nonarteritic anterior ischemic optic neuropathy (NAION - essentially, a stroke of the optic nerve).
When breathing ceases repeatedly throughout sleep, blood and tissue levels of oxygen are diminished significantly, a condition known as ‘chronic intermittent hypoxia.' This lack of oxygen supply disrupts normal cellular metabolism, resulting in thickening of the blood vessel wall with increased risk of both pulmonary hypertension (increased blood pressure within the lungs) and formation of plaques that may occlude blood vessels, leading to stroke and heart attack. The eye contains many blood vessels, so it is not surprising that Obstructive Sleep Apnea Syndrome increases the risk of vascular eye disease.
A recent study conducted in the UK showed that more than half of patients with type 2 diabetes and OSAS have diabetic retinopathy, compared with about 30% of patients with type 2 diabetes and no sleep apnea. These effects were independent of blood glucose control, high blood pressure, age, body mass index and duration of diabetes. In fact, having sleep apnea was more predictive of retinopathy in this analysis than either glycosylated hemoglobin or control of hypertension, two well-established, leading indicators of retinopathy risk. Likewise, the prevalence of glaucoma in patients with sleep apnea in various studies ranges from 7% to 27%, whereas in the general population, glaucoma affects between 1-2% of patients. As for NAION, OSAS has been shown to quintuple the likelihood of this severe eye disease and is believed to be its singular most important risk factor.
Diagnosis and Treatment
A larger neck circumference is associated with Obstructive Sleep Apnea Syndrome: women with a neck size greater than 16 inches and men with a neck size greater than 17 inches are substantially more likely to have sleep apnea. Definitive diagnosis is based on medical and family history, physical examination, and the results of a formal sleep study, called a polysomnogram, which measures breathing and heart rate, eye movement, brain activity, and blood concentrations of oxygen; this is typically performed overnight at a sleep lab. Treatment of sleep apnea includes weight loss and sleeping on your side to prevent airway blockage, as well as avoidance of alcohol and certain medicines. Continuous positive airway pressure (CPAP) is the most common treatment for sleep apnea in adults, and consists of a face or nose mask that gently blows air into the throat. CPAP has been shown to reduce cardiovascular and stroke risk in patients with sleep apnea, and even reduced the risk of death by up to 60% in patients who had already suffered a stroke. Various surgical approaches are also available for Obstructive Sleep Apnea Syndrome.
We have no studies yet to demonstrate that CPAP (or any other sleep apnea treatment) improves pre-existing eye disease, but it seems quite likely. Because diabetic retinopathy, glaucoma, and ischemic optic neuropathy are strongly associated with diabetes and OSAS, patients with these eye disorders should be referred by their eye doctors for testing and treatment of sleep apnea, if appropriate. More importantly, all patients with diabetes should be screened for Obstructive Sleep Apnea Syndrome in order to lower their risk of developing any of the serious vascular complications associated with this common respiratory condition.
For more information on diabetic eye disease, consult Dr. Chous' book Diabetic Eye Disease: Lessons From a Diabetic Eye Doctor, Fairwood Press, Seattle, 2003.
Read more about Dr. Chous here.
Visit Dr. Chous' website here.
NOTE: The information is not intended to be a replacement or substitute for consultation with a qualified medical professional or for professional medical advice related to diabetes or another medical condition. Please contact your physician or medical professional with any questions and concerns about your medical condition.
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