Obstructive sleep apnea may cause early cognitive decline

Obstructive sleep apnea syndrome (OSAS) is a potentially dangerous condition. During sleep, the throat muscles of people with OSAS relax and block airflow into the lungs, so they repeatedly stop breathing. Common symptoms include restless sleep, loud snoring, daytime sleepiness, and prolonged morning headaches, which can be disabling for patients and distressing for their partners.

Sleep apnea: 80% of patients don’t know they have it

Obstructive sleep apnea is currently underdiagnosed: it can occur in 15-30% of men and 10-15% of women, or about 1 billion adults worldwide, of whom about 80% are unaware that they are affected by it. Major risk factors for OSAS include middle age or old age, obesity, smoking, chronic nasal obstruction, high blood pressure, and being male.

On the occasion of a new study, the results of which were published on April 6, 2023 in the journal Frontiers in SleepBritish, German and Australian researchers have shown for the first time that in middle-aged men, OSAS can also cause early cognitive decline, even in patients who are otherwise healthy and not obese.

“OSAS can lead to significant deficits in social cognition”

“We show poorer executive functioning and visuospatial memory and deficits in alertness, sustained attention, and psychomotor and impulse control in men with OSAS. Most of these deficits had previously been attributed to comorbidities”said Dr Ivana Rosenzweig, lead author of the study and a neuropsychiatrist running the Sleep and Brain Plasticity Center at King’s College London, in a communicated. “We have also demonstrated for the first time that OSAS can lead to significant deficits in social cognition”she adds.

Dr. Rosenzweig and her colleagues studied a group of 27 men between the ages of 35 and 70 with a new diagnosis of mild to severe OSAS but without any comorbidities. These patients are relatively rare, as most men and women with OSAS have comorbidities such as cardiovascular and metabolic disease, stroke, diabetes, chronic systemic inflammation, or depression.

The men were not current smokers or alcoholics and were not obese (ie, with a body mass index below 30). As a control, the researchers studied a group of seven men matched for age, BMI and education without OSAS. The diagnosis of OSAS was confirmed by a so-called “WatchPAT” test of their respiratory function during sleep at home, as well as by video-polysomnography at the King’s College sleep centre. With the latter method, the brain waves of sleeping subjects were measured by electroencephalography (EEG), while their blood oxygen levels, heart rate, breathing, and eye and leg movements were tracked.

Many cognitive abilities are affected by sleep apnea

The researchers also tested the subjects’ cognitive function with the Cambridge Neuropsychological Test Automated Battery (CANTAB). Results showed that patients with severe OSAS had lower alertness, executive functioning, short-term visual recognition memory, and social and emotional recognition than matched controls. Patients with mild OSAS performed better in these areas than patients with severe OSAS, but worse than controls.

“The most significant deficits were demonstrated in tests that assess both simultaneous visual matching ability and short-term visual recognition memory for non-verbal schemas, tests of executive functioning, and set change. attention, in alertness and psychomotor functioning, and finally, in social cognition and the recognition of emotions”, wrote the authors.

How does sleep apnea cause cognitive decline?

The authors conclude that OSAS is sufficient to cause these cognitive deficits, which previous studies have attributed to the most common comorbidities of OSAS such as systemic hypertension, cardiovascular and metabolic disease, and type 2 diabetes. hypothesized that cognitive deficits are due to intermittent low oxygen and high carbon dioxide in the blood, changes in blood flow to the brain, sleep fragmentation and neuroinflammation in patients suffering from OSAS.

“This complex interaction is still poorly understood, but it is likely to lead to widespread neuroanatomical and structural changes in the brain and associated functional cognitive and emotional deficits”says Dr. Rosenzweig.