Researchers have shown that obstructive sleep apnea (OSA) causes early cognitive decline in middle-aged men, even in otherwise healthy and non-obese patients. An international study led by King’s College London in the UK looked at a group of 27 men aged 35 to 70 who were newly diagnosed with mild to severe OSA but without any co-morbidities. The researchers published their findings in the journal Frontiers in Sleep.
These patients constituted a rare cohort for the study because men and women with OSA have comorbidities such as cardiovascular and metabolic disease, stroke, diabetes, chronic systemic inflammation, or depression.
Ivana Rosenzweig, lead researcher and neuropsychiatrist. at King’s College London says “We show poorer executive function and visuospatial memory and deficits in vigilance, sustained attention, and psychomotor and impulse control in men with OSA. Most of these deficits were previously attributed to comorbidities, we also show for the first time that OSA can cause significant deficits in social cognition”.
The CANTAB or ‘Cambridge Neuropsychological Test Automated Battery’ tests were used to examine the subjects’ cognitive function.
“The most significant deficits were demonstrated in tests that assess both simultaneous visual matching ability and short-term visual recognition memory for nonverbal patterns, tests of executive functioning and directed attentional set shifting, vigilance, and psychomotor functioning, and finally social cognition and emotion recognition,” the authors wrote.
Obstructive sleep apnea
The authors concluded that OSA is sufficient to induce these cognitive deficits, which previous studies attributed to the most common comorbidities of OSA, such as systemic hypertension, cardiovascular and metabolic disease, and type 2 diabetes.
The men were not current smokers or alcoholics and were not obese (body mass index or BMI below 30). The researchers studied a group of seven men of the same age, BMI and education without OSA as controls. The researchers also confirmed the patients’ OSA diagnosis using the WatchPAT test and video polysomnography.
The WatchPAT test is a sleep apnea diagnostic tool that uses the peripheral arterial signal (PAT) for diagnosis and measures up to 7 channels (PAT signal, heart rate, oximetry, actigraphy, body position, snoring and chest movement) through three contact points. .
However, the researchers said that the mechanism by which this happens is still unclear. The authors speculated that cognitive deficits are caused by intermittent low oxygen and high blood carbon dioxide, changes in cerebral blood flow, sleep fragmentation, and neuroinflammation in OSA patients.
OSA is a condition where during sleep in people with OSA, the neck muscles relax and block the flow of air to the lungs, causing them to repeatedly stop breathing. Common symptoms include restless sleep, loud snoring, daytime sleepiness, and long-lasting morning headaches. Major risk factors for OSA include middle or old age, obesity, smoking, chronic nasal obstruction, high blood pressure, and being male.
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