Table 3.

Mechanisms underlying the relationship between asthma and OSAS.

OSAS (effects on asthma)

OSAS is linked to increased bronchial hyperresponsiveness (2, 56) and may be an independent risk factor for asthma exacerbations (4).

The presence of OSAS is associated with poor asthma control (43) both at daytime and night (57).

OSAS treatment improves asthma symptoms, morning peak flow values, and QoL (46).

Asthma (effects on OSAS)

A higher frequency of roncopathy in atopic women (47) was first reported by a 14-year prospective study showing a pathogenetic role of asthma in sleep respiratory disorder development (48).

Asthma may modify the pharynx collapsibility (58).

During asthma attacks, increased negative intrathoracic pressure may lead to higher pharynx collapsibility (59), which can also arise from decreased respiratory volumes (as in asthma patients) (60).

As asthma is also associated with respiratory muscles weakness and upper ways instability, sleep fragmentation due to asthma with nocturnal symptoms may also induce a loss of slow-waves sleep and cognitive impairment (61).

An additional way from asthma to OSAS is systemic inflammation and use of systemic and inhaled corticosteroids (62, 63). Corticosteroids, frequently prescribed in asthma patients, may lead to a pharyngeal structures remodeling and fatty tissue redistribution (54, 55, 64).

Study on dogs showed that dexamethasone may lead to instability of pharyngeal muscles (“floppy”) reducing their protective effect on upper airways during sleep (65).

Asthma and obesity

Major risk factor and a disease modifier of asthma both in children and adults. Obese subjects have increased risk of asthma.

Obese asthmatics have more symptoms, more frequent and severe exacerbations, a reduced response to medications and an overall decreased quality of life (66).

Different phenotypes within the obese asthma syndrome: those seen in lean individuals complicated by obesity, disease newly arising in obese individuals and phenotypes worsens by increased environmental pollutants response (67).

Different factors contributing to the syndrome of obesity-related asthma: Diet, microbiome, genetic factors, metabolic and immune function, environmental exposures, and mechanical effects (68).

Other conditions and comorbidities

Toxic effect on the pharyngeal mucosa by gastroesophageal reflux, a frequent condition in asthma (69), associated with laryngospasm and neurogenic inflammation (64).

OSAS patients display a higher frequency of acid reflux along with micro-aspiration phenomenon of gastric acid and nocturnal bronchoconstriction (70), thereby establishing a bidirectional relationship.

OSAS, Obstructive Sleep Disorder Syndrome; QoL, Quality of Life.