The US National Sleep Foundation defines sleep apnea as a type of sleep disorder that is marked by abnormal breathing.
It has been known since the beginning of the COVID-19 pandemic that people with underlying health conditions are at a higher risk of more severe disease and negative outcome if they contract the infection. Those with lung disease are expected to be severely affected since COVID-19 is an upper respiratory tract infection and affects the lungs.
However, more and more studies have shown that people with diabetes and hypertension are also likely to suffer more if they contract the infection.
A new study published in Sleep Medicine Reviews now adds another group of people to this list and claims that those with obstructive sleep apnea are at an increased risk of more adverse outcomes from COVID-19 infection. The researchers behind this study, who are based in the University of Warwick, conducted a systematic review of studies to come to this conclusion.
How sleep apnea comes into the COVID-19 picture
The US National Sleep Foundation defines sleep apnea as a type of sleep disorder that is marked by abnormal breathing. There are three types of sleep apnea:
- Obstructive sleep apnea or OSA, where the airway at the back of the throat becomes physically blocked, leading to temporary lapses in breathing.
- Central sleep apnea or CSA, where there is a problem with the brain’s system for controlling muscles involved in respiration, leading to slow and shallow breathing.
- Mixed or complex sleep apnea, where a patient suffers from both OSA and CSA.
As the study in Sleep Medicine Reviews shows, not only does OSA have a higher prevalence, but it also leads to interruptions in breathing, blood oxygen desaturation and arousals from sleep due to partial or complete blockages of the airway during sleep. OSA is also associated with an increased prevalence of many other diseases: hypertension by 39 percent, obesity by 34 percent, depression by 19 percent, gastroesophageal reflux disease (GERD) by 18 percent, diabetes by 15 percent, high cholesterol by 10 percent and asthma by 4 percent.
Many of these diseases co-occurring with OSA have also been identified as risk factors for poor COVID-19 outcomes. And yet, previous studies have not been able to say conclusively if the virus might pose an increased risk for patients with OSA.
strong>Analysing COVID-19 risks for OSA patients
To understand the link between OSA and COVID-19, the researchers looked at 18 studies published up until June 2020 that mentioned both sleep apnea and COVID-19. Of these, only eight were mainly related to the risk of COVID-19 mortality and ten were related to diagnosis, treatment and management. The researchers then found that a number of different biochemical and inflammatory mechanisms of OSA are also associated with COVID-19.
The sleep-time disruptions in breathing that accompany OSA are associated with obesity, intermittent blood gas disturbances (hypoxemia) and increased inflammatory markers. If an OSA patient gets COVID-19, these factors can lead to worsening hypoxemia and the cytokine storm that is not only linked to severe COVID-19 disease but also a subsequent multi-organ failure.
Some studies have shown that increased melatonin, as well as vitamin D levels, may benefit COVID-19 patients. The new study in Sleep Medicine Reviews points out that OSA patients have impaired melatonin regulation and tend to suffer from low vitamin D levels. It may be useful for COVID-19 patients to be screened for OSA and provided with appropriate melatonin and vitamin D supplementation. The study also points out that patients with idiopathic pulmonary fibrosis (IPF) also present with OSA as comorbidity and IPF and other fibrotic changes have been observed in COVID-19 patients too.
It’s therefore important, the researchers say, to also screen COVID-19 patients with IPF for OSA and consider viable therapeutic options for them. The researchers also indicate that further studies into the causal relationship between COVID-19 and OSA should be conducted soon to make proper aid available to patients worldwide.
