What is the link between sleep apnea and the nasal microbiota?
Obstructive sleep apnea is associated with a modification of the nasal microbiota and increased inflammation, two events which are thought to be self-sustaining and to exacerbate the disorder, according to a new study.
Sleep apnea is a common disorder associated with inflammation of the upper airway, systemic inflammation and a modified immune response. To what extent is the nasal microbiota involved in these different events? And how do they influence its composition? To answer these questions, a team of researchers recruited 565 volunteers from two cohorts taking part in sleep studies. Two-thirds of the first group were suffering from obstructive sleep apnea (OSA), considered severe in 9.5% of them. Almost three-quarters of the second group had OSA, 45% of whom had the severe form. After having subjected all participants to nasal irrigation, the researchers analyzed the nasal microbial composition of apneic patients and then compared it with that of healthy individuals.
A more diversified microbiota in patients with severe OSA
The results show that OSA is not reflected as a variation in the abundance of the nasal microbiota, which remains dominated by two bacterial species: Staphylococcus and Corynebacterium. However, it is associated with greater species diversity, which is more marked when the disorder is more severe. The species which enrich this flora are usually found in the oral microbiota (Streptococcus, Prevotella, Veillonella, Granulicatella).
More inflammatory markers
The authors suggest that the origin of this migration could, amongst other factors, lie in airway obstruction creating a reflux of oropharyngeal secretions (at the back of the oral cavity), which are normally swallowed, or in impaired nasal filtration in patients with severe apnea. The authors moreover observed the enhanced presence of nasal inflammatory markers in the apneic patients, and noted that they influenced the nature of the bacteria making up the microbiota which lines the nose.
A therapeutic approach
Continuous positive pressure treatment (CPP), the therapeutic gold standard which consists in preventing closure of the upper airway, had no effect on the diversity and composition of the microbiota. Nevertheless, this study confirms that the dysbiosis observed in the apneic patients is associated both with the disorder and inflammation, although its cause remains to be elucidated. It also allows a new approach to be considered in the treatment of severe apnea, through investigation of the role of the secretions contained in the reflux.
Wu BG et al. Severe Obstructive Sleep Apnea is Associated with Alterations in the Nasal Microbiome and Increase in Inflammation. American Journal of Respiratory and Critical Care Medicine https://www.atsjournals.org/doi/10.1164/rccm.201801-0119OC