Experiments on primates with blocked nasal passages have demonstrated significant effects on the development and function of oral and craniofacial structures. These studies highlight how extended periods of oral breathing, caused by nasal obstruction, can influence growth patterns, dental alignment, and overall health.
It has been maintained that because of large adenoids, nasal breathing is obstructed leading to mouth breathing and an ‘adenoid face’, characterized by an incompetent lip seal, a narrow upper dental arch, increased anterior face height, a steep mandibular plane angle, and a retrognathic mandible. This development has been explained as occurring by changes in head and tongue position and muscular balance. After adenoidectomy and change in head and tongue position, accelerated mandibular growth and closure of the mandibular plane angle have been reported. Children with obstructive sleep apnea (OSA) have similar craniofacial characteristics as those with large adenoids and tonsils, and the first treatment of choice of OSA children is removal of adenoids and tonsils. It is probable that some children with an adenoid face would nowadays be diagnosed as having OSA. These children also have abnormal nocturnal growth hormone (GH) secretion and somatic growth impairment, which is normalized following adeno-tonsillectomy. It is hypothesized that decreased mandibular growth in adenoid face children is due to abnormal secretion of GH and its mediators. After normalization of hormonal status, ramus growth is enhanced by more intensive endochondral bone formation in the condylar cartilage and/or by appositional bone growth in the lower border of the mandible. This would, in part, explain the noted acceleration in the growth of the mandible and alteration in its growth direction, following the change in the mode of breathing after adeno-tonsillectomy.
Mouth breathing, particularly when caused by chronic nasal obstruction, can have significant effects on overall health, including potential impacts on growth hormone (GH) secretion.
Key Points on Mouth Breathing and GH Secretion:
1. Sleep Disruption and GH Secretion: Growth hormone is primarily secreted during deep sleep, especially during slow-wave sleep (SWS). Mouth breathing, often associated with sleep-disordered breathing (such as obstructive sleep apnea), can lead to fragmented sleep and reduced time spent in deep sleep stages. This disruption can result in decreased GH secretion, which is critical for growth, metabolism, and tissue repair.
2. Impact on Physical Growth: In children, chronic mouth breathing due to nasal obstruction has been linked to altered growth patterns. Since GH plays a vital role in growth and development, any reduction in its secretion can contribute to growth delays or stunted growth. This is particularly concerning during critical periods of development.
3. Indirect Effects via Sleep Apnea: Studies on children with obstructive sleep apnea, a condition often associated with mouth breathing, show that these children may have reduced GH secretion. This is because the repeated arousals and poor sleep quality associated with apnea can diminish the overall production of growth hormone.
Research Evidence
Research in humans and animal models supports the connection between sleep quality, GH secretion, and mouth breathing. While specific studies directly linking mouth breathing to reduced GH levels in humans may be limited, the broader body of research on sleep-disordered breathing and GH secretion provides substantial evidence of this relationship.
Chronic mouth breathing, particularly when it leads to sleep disruption, can have a negative impact on growth hormone secretion, potentially leading to growth and developmental issues, especially in children. Addressing the underlying causes of mouth breathing, such as nasal obstruction, is essential to mitigate these effects.