When dealing with sleep apnea, fear and anxiety always seem to be close by. Many sleep apnea sufferers have recounted stories of waking up in fear in the middle of night or having outright panic attacks. Some have suspected that there was a medical explanation and recent studies have emerged to back this up.

A study published in 2009 concluded that patients exhibiting central sleep apnea are three times more likely to have an anxiety disorder than are those with no evidence of central apnea. It was found that 66% of the patients had at least one central or obstructive apnea event during their polysomnographic examination. After adjusting for sleep parameters such as sleep efficiency, percent of REM sleep, and apneahypopnea index; demographic covariates such as sex, BMI, age, and caffeine, alcohol, and tobacco consumption; and history of medical and psychiatric disorders, the researchers determined that the odds ratio for anxiety in patients with at least one CSA event was 3.0, which was statistically significant.

Another interesting study explored why sleep apnea can trigger anxiety and panic attacks to begin with. This study by University of Iowa researchers shows that carbon dioxide increases brain acidity, which triggers a protein that is central to fear and anxiety behavior. Researchers focussed on a brain protein known as acid-sensing ion channel 1a (ASIC1a), which is abundant in the amygdala — the region deep in the brain that processes fear signals and directs fear behavior. Blocking or removing ASIC1a is known to reduce innate fear and alters fear memory in mice. Scientists have known since 1918 that increased levels of carbon dioxide can produce abnormal behavior with those known to have anxiety disorders. The study team also found that making brain tissue less acidic blunted fear behaviour produced by carbon dioxide and reduced learned fear. They go on to suggest that breathing exercises could have anti-anxiety effects as well.