As many as 25 million Americans suffer from obstructive sleep apnea (OSA), a sleep disorder that represents a major danger to the brain. OSA heightens risk for potentially brain-damaging physical conditions, such as high blood pressure, stroke, heart disease, and diabetes. In addition, people with the sleep disorder—the vast majority of whom remain undiagnosed—often experience mental symptoms, such as difficulty with concentration and decision-making, poor memory, major depression and stress.
“The number of Americans with OSA is staggering, and most likely related to the obesity epidemic our nation is experiencing,” says Kenneth Sassower, MD, an MGH neurologist and expert in sleep disorders. “If OSA is not diagnosed and treated, it may cause brain injury that leads eventually to cognitive impairment, depression, and greater risk for dementias such as Alzheimer’s disease (AD) and vascular dementia. Fortunately, effective treatments are available to restore normal sleep and reverse OSA-related brain injury, which means that identifying and managing the condition would likely translate into prevention or delay of mental impairment in many seniors.”
WHAT CAN YOU DO?
re you at risk for OSA? You are more likely to develop OSA if you:
- Are obese or overweight.
- Are over 65 years old.
- Have high blood pressure or allergies.
- Are male.
- Are related to someone who has sleep apnea.
- Have certain physical attributes, such as a deviated septum, a receding chin, an abnormally narrow airway, or enlarged tonsils or adenoids.
- Drink to excess, use sedatives, or smoke.
OSA is characterized by periodic and repeated closures of the airway during sleep. The throat muscles sag, narrowing the airway and briefly interrupting breathing and/or causing loud snoring, gasping, and choking that can trigger repeated awakenings. Frequent morning headache, dry mouth or sore throat, and excessive daytime drowsiness may also be indications of the sleep disorder. Dr. Sassower advises people with these symptoms to seek medical evaluation.
Although vulnerability to OSA may be related to factors beyond the individual’s control (See What You Should Know for OSA risk factors), there are a number of lifestyle strategies that may help lower a person’s risk for the sleep disorder or help to reduce its symptoms. These strategies include:
▶ Weight loss. Excess weight is associated with a higher incidence of OSA, as is a larger neck size, since this may indicate the presence of fatty tissue that can narrow the airway. Men with neck circumferences of 17 inches or more, and women with circumferences of 15 inches or more are at greater risk. Research suggests that losing weight and maintaining a healthy weight are some of the most effective ways to conquer OSA.
▶ Controlling hypertension (high blood pressure). More than 33 percent of individuals with hypertension and 80 percent with treatment-resistant hypertension have OSA, which has been found to significantly increase the risk for a brain-damaging stroke. If you are among the 36 percent of Americans whose hypertension is not controlled, seek treatment to lower your blood pressure (aim for a systolic reading of 139 or less, and a diastolic reading of 89 or less) and ask your doctor about your risk for OSA.
▶ Smoking cessation. Smoking damages the cardiovascular system and compounds the brain damage caused by OSA-related lack of oxygen to the brain, in addition to all its other negative effects on health.
▶ Avoiding substance abuse. Excessive alcohol consumption (more than two drinks per day for men, and one drink per day for women), especially close to bedtime, is associated with greater risk for OSA because heavy drinking tends to promote relaxation of throat muscles. Sedating drugs also act to relax throat muscles, and their use should be limited or avoided if possible, especially at night.
▶ Controlling allergies to reduce inflammation that interferes with breathing.
▶ Using a saline nasal spray or breathing strips (external nasal dilators) to clear nasal passages and make breathing easier.
▶ Adjusting your sleep position. Symptoms of OSA are associated with sleeping on your back. Sleeping on your side or elevating your head with a cervical pillow or by raising the head of your bed about four inches can often help open airways.
▶ Improving your overall sleep hygiene through strategies such as exercising regularly, maintaining a regular sleep schedule, and avoiding heavy meals or caffeine close to bedtime.
It is not yet known precisely how OSA causes cognitive impairment; however, scientists have identified a number of potentially damaging brain changes associated with the disorder.
A paper published in the August 2016 issue of the Journal of Sleep Research suggests significant alterations in two brain chemicals—the neurotransmitters gamma-aminobutyric acid (GABA), which helps slow brain activity and promote feelings of calm, and glutamate, which acts to boost brain activity, but at high levels can cause stress and damage nerve calls in the hippocampus and other key memory regions. In the people with OSA whom they studied, researchers found unusually low levels of GABA and abnormally high levels of glutamate. The findings suggest that OSA changes the way the brain works, and that developing treatments to help restore normal levels of neurotransmitters might help reverse OSA symptoms.
Other research has linked sleep apnea to deterioration of the brain’s white matter in certain regions, metabolic problems involving insulin that interfere with the delivery of nutrients to brain cells, and chronic oxygen deprivation that leads to the injury and death of neurons. Brain function may be affected further when repeated awakenings and sleep deprivation impair memory consolidation that occurs during sleep and lead to fatigue and depression that impairs not only memory, but also critical functions such as attention, decision-making and thinking.
“More than half of people with OSA have symptoms of depression, and it is well documented that depression increases the risk for sleep problems and cognitive impairment,” says Dr. Sassower. “The two conditions seem to be interrelated, so that treating both may well result in an improvement in mood that, in turn, leads to better sleep and better cognition, and vice versa.”
Treatment for OSA usually involves adherence to healthy lifestyle strategies and the use of devices designed to increase oxygen delivery to the brain. These include the continuous positive airflow pressure device (CPAP, which delivers a constant flow of air into breathing passages through a mask covering the nose and mouth) and dental devices designed to reposition the lower jaw or tongue in order to open the airway during sleep.
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