Elsevier

Medical Hypotheses

Volume 103, June 2017, Pages 96-99
Medical Hypotheses

Rhinitis and sleep disorders: The trigeminocardiac reflex link?

https://doi.org/10.1016/j.mehy.2017.04.019Get rights and content

Abstract

Rhinitis, allergic or non-allergic, is an inflammatory condition of the nose. It is associated with a wide range of sleep disorders that are generally attributed to nasal congestion and presence of inflammatory mediators like cytokines and interleukins. However, the pathophysiological mechanisms behind these sleep disorders remain unclear. On the other hand, the trigeminocardiac reflex (TCR) has recently been linked to various sleep disorders like obstructive sleep apnea, sleep bruxism and rapid eye movement (REM) sleep apnea. TCR can be incited by stimulation of the trigeminal nerve or the area innervated by its branches including the nasal mucosa. Trigeminal nasal afferents can be activated on exposure to noxious stimuli (mechanical or chemical) like ammonia vapors, carbon-dioxide, nicotine, hypertonic saline, air-puffs and smoke. In rhinitis, there is associated neuronal hyper-responsiveness of sensory nasal afferents due to inflammation (which can be suppressed by steroids). This may further lead to increased occurrence of TCR in rhinitis. Moreover, there is involvement of autonomic nervous system both in rhinitis and TCR. In TCR, parasympathetic over activity and sympathetic inhibition leads to sudden onset bradycardia, hypotension, apnea and gastric motility. Also, the autonomic imbalance reportedly plays a significant role in the pathophysiology of rhinitis. Thus, considering these facts we hypothesize that the TCR could be the link between rhinitis and sleep disorders and we believe that further research in this direction may yield significant development in our understanding of sleep disorders in rhinitis.

Introduction

Rhinitis, allergic as well as non-allergic, is a common respiratory condition that may often be chronic. Allergic rhinitis (AR) is a multifactorial condition with both inflammation and neurological involvement (neurogenic inflammation) playing significant roles [1]. Nasal congestion, seen in rhinitis, is a known risk factor for sleep-disordered breathing (including snoring, hypopnea, apnea), [2] while inflammation has been associated with suppression of both REM and NREM sleep [3]. The relationship between rhinitis, nasal obstruction and sleep disordered breathing is well established [4]. The resulting sleep impairment can have significant impact on quality of life. However, the mechanisms underlying sleep disorders in rhinitis are still not well established.

In recent years, trigeminocardiac reflex (TCR), one of the most powerful autonomic reflexes of the body, has been found to have a role in sleep disorders like sleep bruxism (SB), sleep apnea (SA) and obstructive sleep apnea (OSA) [5]. Another variant of the TCR, the diving reflex (DR), has recently been linked to sudden infant death syndrome (SIDS) [6] where there is unexplained death of a seemingly healthy infant, usually during asleep. The TCR can be activated by stimulation of the trigeminal nerve anywhere along its course and manifests as mild to severe negative cardiorespiratory changes such as bradycardia, asystole, hypotension or apnea, due to sympathetic withdrawal and parasympathetic overactivity via the vagus nerve. Various subtypes of the TCR are reported and include the peripheral TCR (occulocardiac reflex, nasocardiac reflex, maxillomandibular reflex), gasserian ganglion type and the central TCR [7]. The TCR assumes significance in clinical practice as its role in various neurosurgical and maxillofacial procedures is well established [8]. This reflex can be elicited by either mechanical, chemical or electrical stimuli [9] in the areas innervated by trigeminal nerve such as surgery, cold exposure, smoke, secretions or inflammation. Here, we intend to hypothesize the role of the TCR in nasal inflammation/ infection (rhinitis) associated sleep disorders.

Section snippets

The hypothesis/theory

Allergic rhinitis and non-allergic rhinitis (NAR) are associated with a high incidence of different sleep disorders. In addition, there exists an autonomic imbalance in rhinitis, with parasympathetic overactivity. Also, the DR has been reported to be exaggerated in non-eosinophilic non-allergic rhinitis (NENAR) [10]. On the other hand, TCR has been implicated in sleep disorders like REM sleep apnea, SB and OSA [5]. It is also speculated that the nasotrigeminal reflex, a form of TCR, may have a

Rhinitis and sleep disorders

AR affects up to 40% of population worldwide [15]. It occurs due to air borne particles (allergens) in people who are allergic to them [16] and is an important cause of nasal congestion. Sneezing, nasal obstruction, rhinorrhea and nasal itching are the most common signs of AR [17]. NAR most commonly presents with nasal obstruction and rhinorrhea, while sneezing and itching are less common [18].

Typical sleep disorders seen in AR include sleep disordered breathing (SDB), sleep apnea and snoring.

Consequences of hypothesis and discussion

AR affects a wide percentage of population with reported prevalence of up to 40% in both children and adults. Approximately 80% of them are symptomatic before the age of 20 years [30]. Upto 68% of those with perennial AR and 48% of those with seasonal AR report sleep disturbances [31]. Apart from this, AR can directly cause impaired cognition, reduced productivity, impaired work performance and learning impairment in children. These effects are likely to be exaggerated by sleep impairment [32].

Funding

None.

Conflict of interest

None to declare.

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