Sleep apnea syndrome has a certain genetic tendency, but not everyone will inherit it.
Sleep apnea is associated with multiple factors, including genetics. Studies have linked mutations in certain genes, such as the leptin receptor gene and the perineuronal protein gene, to the development of sleep apnea.
Abnormal expression of these genes may lead to structural abnormalities or muscle dysfunction in the upper airway, thus causing sleep apnea. Therefore, people with a family history of the condition may be at increased risk.
Studies have shown that family history is an important risk factor, and genetics may increase the risk of disease by affecting maxillofacial structure, fat distribution, and respiratory control function. However, environmental factors, such as obesity and lifestyle, also play a key role.
How Do Genetic Factors Affect Sleep Apnea?
1.Abnormal Craniofacial Structure
Genetics may affect upper airway anatomy (such as mandibular retraction and velopharyngeal stenosis), leading to airway collapse. Studies have found that approximately 30%-40% of craniofacial features are related to genetics. Even people with normal weight may be susceptible to airway stenosis.
2.Obesity And Fat Distribution
Approximately 70% of patients with OSA are obese, and body mass index (BMI) and fat distribution patterns are hereditary. For example, fat accumulation in the neck can compress the airway, while excess abdominal fat can impair respiratory muscle function.
3. Defects In Respiratory Regulation
Some patients have genetic abnormalities in neural regulation, which reduces the sensitivity of the respiratory center to low oxygen or high carbon dioxide levels during sleep, making them prone to sleep apnea.
4. Inflammation And Metabolism-related Genes
Systemic inflammatory responses and metabolic disorders often accompany OSA. Certain genes (such as the hypoxia-inducible factor gene) may indirectly increase the risk of the disease by regulating the levels of inflammatory factors.
5. Sleep And Circadian Rhythm Regulation
A person’s genes can influence their innate sleep schedule, sleep quality, and whether they suffer from other sleep disorders.
The activity of the nerve cells that control breathing in our bodies is affected by our sleep and wakefulness.
Research has found that families often share similar sleep habits and circadian rhythms (such as when they feel sleepy and wake up), suggesting that these traits can be inherited.
Sleep, circadian rhythm, melanin secretion, and body temperature regulation are all controlled by an area in the brain called the suprachiasmatic nucleus, which is like the “biological clock commander” of the human body.
Studies of families with advanced sleep phase syndrome (characterized by consistently going to bed early and waking up early) have found that their sleep-wake times are generally advanced, and their melatonin secretion and body temperature rhythms are abnormal. This condition is inherited in an autosomal dominant manner, meaning that if one parent has the condition, the child is likely to also develop the same symptoms.
Genetic Factors For Sleep Apnea
1.Genes That Cause Obesity
Sleep apnea syndrome (SAHS) is linked to genetics, particularly genes that predispose to obesity.
These genes include leptin, which controls appetite; β3-adrenergic receptors, which influence energy expenditure; tumor necrosis factor-α, which is involved in inflammation; and insulin-like growth factor 1 and its receptor, which regulate growth.
These genes often affect multiple body functions, not only involving obesity, but may also be directly or indirectly involved in the occurrence of apnea.
(1) Leptin
Leptin is a substance that controls appetite and energy consumption, affects a person’s weight and fat distribution, and is closely related to insulin resistance (which can easily lead to diabetes).
Research has found that certain genetic variants of the leptin receptor are associated with obesity. Among patients with sleep apnea-related sleep apnea (SAHS), higher levels of obesity are associated with higher leptin levels.
Furthermore, after six months of effective CPAP treatment, patients experienced a decrease in leptin levels, which was associated not only with weight loss but also with a reduction in the number of apneas.
(2) HLA-A2 Antigen
A study found that people with sleep apnea syndrome (SAHS) are nearly twice as likely to carry the genetic marker HLA-A2 as those without the condition. Furthermore, SAHS patients with HLA-A2 are significantly more obese than those without the marker.
This suggests a link between HLA-A2, obesity, and sleep apnea, but it’s unclear whether HLA-A2 causes obesity and subsequently sleep apnea, or whether the gene directly influences both conditions. Further research is needed to understand the underlying mechanisms.
(3) Tumor Necrosis Factor-alpha (TNF-α)
Tumor necrosis factor-α (TNF-α) is a substance involved in inflammatory responses in the human body. Studies have found that its overexpression in adipose tissue is closely associated with obesity and insulin resistance (a poor insulin response, which can lead to diabetes).
Specifically, people with certain variants of the TNF-α gene (such as -308A) tend to have higher body mass index (BMI), more pronounced insulin resistance, and even higher leptin levels. Recent studies have also found that among people with type 1 diabetes, those with the A variant of the gene are more insulin-resistant, though other studies have reached different conclusions.
Serum TNF-α levels are significantly higher in patients with obstructive sleep apnea (OSAHS) than in healthy controls, particularly at night when blood oxygen saturation falls below 85%.
The TNF-α secretion rhythm is also disrupted: the peak of secretion, which is typically higher at night, disappears and instead occurs during the day. Even when CPAP therapy alleviates apnea symptoms, the TNF-α rhythm remains difficult to normalize, suggesting that it may be a fundamental factor in the disease.
This elevated TNF-α is not associated with obesity but is positively correlated with the frequency of apnea hypopnea (AHI). High levels of TNF-α and another inflammatory cytokine, IL-6, also lead to daytime sleepiness, suggesting they may directly influence symptoms. Furthermore, elevated TNF-α can weaken throat and respiratory muscles, further exacerbating nocturnal apnea.
2.Genes For Face And Jaw Shape
Sleep apnea syndrome (SAHS) is sometimes linked to genes that influence facial and jaw shape.
Genes such as transforming growth factor-β (TGF-β) and retinoic acid receptors play a key role in the development of these structures.
Studies have found that mice lacking the TGF-β gene develop facial deformities such as a retracted chin and a small jaw, demonstrating that this gene is crucial for the normal development of the cranial and facial skeleton. TGF-β is also involved in lung development and the development of some lung diseases, and abnormal changes in it can even precede the onset of lung function problems.
However, no significant differences in TGF-β levels have been found between SAHS patients and healthy controls.
Additionally, mutations in the retinoic acid receptor gene can also cause facial and jaw morphological abnormalities.
Structural issues such as a receding chin and a small jaw are common risk factors for SAHS. Therefore, further research is needed to clarify the specific relationship between these genes and sleep apnea.
3.Genes That Control Breathing
Sleep apnea syndrome (SAHS) is associated with several genes that affect respiratory control, including ET-1, RET, and brain-derived neurotrophic factor (BDNF).
Research has found that mice with the ET-1 gene deleted develop symptoms similar to SAHS, including respiratory failure, abnormal respiratory control, maxillofacial developmental problems, and hypertension. These mice also exhibit significantly reduced responses to hypoxia and high carbon dioxide levels.
Knockout of the RET gene reduced mice’s response to high carbon dioxide levels. Mice lacking the BDNF gene, however, exhibited irregular breathing rhythms and were prone to apnea, particularly in response to hypoxia.
Although these results are primarily from animal studies and have not yet been validated in humans, they provide important clues to our understanding of the genetic mechanisms of respiratory control.
Furthermore, certain variants of the ACE gene (such as the I allele) can reduce ACE activity in the body, potentially enhancing the body’s ability to adapt to high-altitude hypoxia and improving blood oxygen saturation.
Recent studies have also suggested that the human response to hypoxia may be influenced by the ACE genotype and that polymorphisms in this gene may also be associated with the development of SAHS.
4.Genes That Influence Sleep And Biological Clocks
The occurrence of obstructive sleep apnea syndrome (OSAHS) is related to some genes that affect sleep and biological clocks, mainly including Orexin and hPer2 genes.
Orexin is a substance that promotes wakefulness and reduces deep sleep. Without this gene, laboratory mice develop symptoms similar to narcolepsy, including difficulty staying awake and disrupted transitions between sleep and wakefulness.
Another genetic disorder, familial advanced sleep phase syndrome (which causes people to fall asleep and wake up very early), has been linked to mutations in the hPer2 gene, which can cause changes in the body’s circadian rhythms.
How to Reduce Genetic Risk?
1.Weight Management
Even with genetic susceptibility, controlling weight (BMI < 25) can reduce the risk of developing the disease by more than 50%. Reducing visceral fat can significantly alleviate airway pressure.
2. Improve Sleeping Habits
Measures such as sleeping on your side (to reduce tongue drop), avoiding alcohol (to reduce throat muscle tension), and treating nasal congestion (to keep the nasal cavity open) can help reduce sleep apnea.
3. Early Screening And Intervention
Polysomnography (PSG) is recommended for those with a family history, especially if they have snoring, daytime sleepiness, or other symptoms. Children with adenoid hypertrophy or maxillofacial abnormalities require prompt correction.
4. Targeted Training
Oral muscle training (such as playing wind instruments and pronunciation exercises) can strengthen pharyngeal muscle tension; continuous positive airway pressure (CPAP) therapy can effectively improve symptoms.
