LONDON — Snoring could be a sign that cognitive decline will appear sooner rather than later, a new study explains. Researchers in London say sleep apnea, which often causes patients to snore heavily, cuts off blood and oxygen to the brain — destroying neurons in the process.
According to a 2017 report by American Academy of Sleep Medicine (AASM), OSA affects 12 percent of U.S. adults. That’s approximately 30 million people. Moreover, four in five cases go undiagnosed. The walls of the throat relax and narrow, interrupting normal breathing several times a night.
“We show poorer executive functioning and visuospatial memory and deficits in vigilance, sustained attention, and psychomotor and impulse control in men with OSA. Most of these deficits had previously been ascribed to co-morbidities,” says lead author Dr. Ivana Rosenzweig, a neuropsychiatrist who heads the Sleep and Brain Plasticity Center at King’s College London, in a media release.
“We also demonstrated for the first time that OSA can cause significant deficits in social cognition.”
The findings are based on 27 otherwise healthy 35 to 70-year-old men who visited the clinic with a new diagnosis of mild to severe OSA. Such patients are relatively rare as most will also have conditions like obesity, cardiovascular and metabolic disease, stroke, diabetes, chronic systemic inflammation, or depression.
Those with severe OSA had worse vigilance, executive functioning, short-term visual memory, and social and emotion recognition. This was compared to a group of healthy controls without the sleep disorder who the team matched based on age, BMI (body mass index), and education.
Results show OSA is serious enough to cause loss of brainpower, which has been previously linked to high blood pressure, cardiovascular and metabolic diseases, and Type 2 diabetes. The phenomenon could be due to intermittent low oxygen and high carbon dioxide in the blood, changes in blood flow to the brain, sleep fragmentation, and neuroinflammation in OSA patients.
“This complex interplay is still poorly understood, but it’s likely that these lead to widespread neuroanatomical and structural changes in the brain and associated functional cognitive and emotional deficits,” Rosenzweig says.
OSA is highly debilitating for patients and their partners. It’s a potentially life-threatening condition. Symptoms include loud snoring, restless sleep, daytime napping, and prolonged morning headaches. It may occur in up to 30 percent of men and 15 percent of women — around one billion adults worldwide.
Major risk factors include middle or old age, being obese, smoking, chronic nasal blockage, high blood pressure, and being male. Dr. Rosenzweig’s team, along with colleagues in Germany and Australia, have now shown for the first time that sleep apnea can cause early cognitive decline in middle-aged men.
The participants were not current smokers or alcohol abusers and had a BMI below 30. Doctors confirmed sleep apnea diagnoses by respiratory function tests during sleep at home and in the King’s College lab. The group also wore EEG (electroencephalography) skull caps which measure brain waves, while the team tracked blood oxygen levels, heart rate, breathing, and eye and leg movements. Whether comorbities have similar negative effects on cognition above and beyond those directly resulting from OSA is not yet clear.
“Our study is a proof of concept. However, our findings suggest that co-morbidities likely worsen and perpetuate any cognitive deficits caused directly by OSA itself,” the study author continues. “What remains to be clarified in future studies is whether co-morbidities have an additive or synergistic effect on the latter deficits, and whether there is a difference in brain circuitry in OSA patients with or without co-morbidities.”
Overweight individuals are particularly prone to sleep apnea. Preventative measures include shedding excess weight or wearing a mask in bed which blows air into the back of the throat. The condition blights the lives of up to one in eight people. Diabetics, smokers, and drinkers are particularly at risk.
Twice more common in men than women, it can begin at any time, including during childhood. According to the CDC, roughly six million Americans suffer from Alzheimer’s disease or other forms of dementia.
The study is published in the journal Frontiers in Sleep.
South West News Service writer Mark Waghorn contributed to this report.