In a pilot study out of King’s College London, participants with severe OSA experienced worse executive functioning as well as social and emotional recognition versus healthy controls.
Major risk factors for OSA include obesity, high blood pressure, smoking, high cholesterol, and being middle-aged or older. Because some researchers have hypothesized that cognitive deficits could be driven by such comorbidities, the study investigators recruited middle-aged men with no medical comorbidities.
“Traditionally, we were more concerned with sleep apnea’s metabolic and cardiovascular comorbidities, and indeed, when cognitive deficits were demonstrated, most were attributed to them, and yet, our patients and their partners/families commonly tell us differently,” lead investigator Ivana Rosenzweig, MD, PhD, of King’s College London, who is also a consultant in sleep medicine and neuropsychiatry at Guy’s and St Thomas’ Hospital, London, said in an interview.
“Our findings provide a very important first step towards challenging the long-standing dogma that sleep apnea has little to do with the brain – apart from causing sleepiness – and that it is a predominantly nonneuro/psychiatric illness,” added Dr. Rosenzweig.
The findings were published online in Frontiers in Sleep.
Brain changes
The researchers wanted to understand how OSA may be linked to cognitive decline in the absence of cardiovascular and metabolic conditions.
To accomplish this, the investigators studied 27 men between the ages of 35 and 70 with a new diagnosis of mild to severe OSA without any comorbidities (16 with mild OSA and 11 with severe OSA). They also studied a control group of seven men matched for age, body mass index, and education level.
The team tested participants’ cognitive performance using the Cambridge Neuropsychological Test Automated Battery and found that the most significant deficits for the OSA group, compared with controls, were in areas of visual matching ability (P < .0001), short-term visual recognition memory, nonverbal patterns, executive functioning and attentional set-shifting (P < .001), psychomotor functioning, and social cognition and emotional recognition (P < .05).
On the latter two tests, impaired participants were less likely to accurately identify the emotion on computer-generated faces. Those with mild OSA performed better than those with severe OSA on these tasks, but rarely worse than controls.
Dr. Rosenzweig noted that the findings were one-of-a-kind because of the recruitment of patients with OSA who were otherwise healthy and nonobese, “something one rarely sees in the sleep clinic, where we commonly encounter patients with already developed comorbidities.
“In order to truly revolutionize the treatment for our patients, it is important to understand how much the accompanying comorbidities, such as systemic hypertension, obesity, diabetes, hyperlipidemia, and other various serious cardiovascular and metabolic diseases and how much the illness itself may shape the demonstrated cognitive deficits,” she said.
She also said that “it is widely agreed that medical problems in middle age may predispose to increased prevalence of dementia in later years.
Moreover, the very link between sleep apnea and Alzheimer’s, vascular and mixed dementia is increasingly demonstrated,” said Dr. Rosenzweig.
Although women typically have a lower prevalence of OSA than men, Dr. Rosenzweig said women were not included in the study “because we are too complex. As a lifelong feminist it pains me to say this, but to get any authoritative answer on our physiology, we need decent funding in place so that we can take into account all the intricacies of the changes of our sleep, physiology, and metabolism.
“While there is always lots of noise about how important it is to answer these questions, there are only very limited funds available for the sleep research,” she added.
Dr. Rosenzweig’s future research will focus on the potential link between OSA and neuroinflammation.
In a comment, Liza Ashbrook, MD, associate professor of neurology at the University of California, San Francisco, said the findings “add to the growing list of negative health consequences associated with sleep apnea.”
She said that, if the cognitive changes found in the study are, in fact, caused by OSA, it is unclear whether they are the beginning of long-term cognitive changes or a symptom of fragmented sleep that may be reversible.
Dr. Ashbrook said she would be interested in seeing research on understanding the effect of OSA treatment on the affected cognitive domains.
The study was funded by the Wellcome Trust. No relevant financial relationships were reported.
A version of this article originally appeared on Medscape.com.