OSAHS is a disease that occurs during sleep and is characterized by repeated blockages or narrowing of the upper airway (including the nasal cavity, oral cavity, and throat) during sleep, leading to reduced or even complete cessation of airflow.
This condition can cause patients to experience loud and uneven snoring, sleep apnea (i.e., snoring suddenly stops, and airflow through the mouth and nose is interrupted for several seconds or even longer), and decreased blood oxygen levels due to difficulty breathing during sleep at night.
Because breathing interruptions repeatedly disrupt normal sleep patterns, patients may experience significant daytime drowsiness and fatigue, difficulty concentrating, and impaired memory, even after sleeping for a sufficient amount of time.
Without effective intervention, this condition can also increase the risk of developing chronic diseases such as hypertension, heart disease, cerebrovascular disease, and diabetes.
Bronchial asthma is a chronic inflammatory disease of the airways. This inflammation is not caused by infection, but is related to physical and environmental factors, leading to an oversensitivity of the airways to various irritants (such as allergens, cold air, smoke, etc.).
When stimulated, the airway walls swell, smooth muscles contract, and excessive mucus may be produced. These changes together narrow the airway lumen, obstructing airflow.
As a result, patients will experience recurrent episodes of wheezing (with a whistling sound during breathing), shortness of breath, chest tightness, or coughing.
These symptoms are especially likely to appear or worsen at night or in the early morning.
An important characteristic is that this airflow limitation is usually reversible, meaning that the symptoms of difficulty breathing can be relieved and the airway can be restored after using certain medications or on its own.
OSAHS and bronchial asthma are two common diseases that seriously affect people’s health. A growing body of research shows a close link between these two diseases, often influencing each other and even occurring simultaneously in the same patient.
Specific data shows that up to 52% of OSAHS patients also suffer from asthma, with 33.6% of these having severe asthma.
On the other hand, sleep monitoring among asthma patients revealed that approximately 66% had sleep apnea (more than 5 apnea or shortness-of-breath episodes per hour), with 43% experiencing significant problems (more than 15 episodes per hour).
This reflects that asthma patients are more prone to OSAHS, and once they also have OSAHS, asthma patients often experience more frequent and intense nighttime symptoms, requiring higher medication dosages and making overall disease control more difficult.
The Correlation Between Asthma and OSAHS
Asthma patients often experience symptoms such as snoring, sleep apnea, and daytime sleepiness.
A Swedish study, after controlling for age, gender, and smoking habits, found that the incidence of snoring in the general population was 10.7%, rising to 21.3% in people with recurrent wheezing, and 17.0% in patients diagnosed with asthma.
The incidence of sleep apnea is 6.8% in the general population, 17.1% in those with recurrent wheezing, and 14.3% in those diagnosed with asthma.
Furthermore, a survey using the Berdin Questionnaire confirmed that the proportion of OSAHS-related symptoms is significantly higher in asthma patients than in the general population.
Asthma patients also have a higher risk of developing OSAHS in the future.
An eight-year long-term follow-up study conducted by the Wisconsin Sleep Research Center (starting in 1988) showed that among 205 asthma patients, 84 (41%) eventually developed OSAHS; while among 1287 participants without a history of asthma, only 369 (29%) developed the condition, and the difference between the two groups was statistically significant.
The study further indicated that individuals with a history of asthma had a 76% increased risk of developing OSAHS eight years later compared to those without a history of asthma, with this risk being more pronounced in children.
However, the study also found no significant difference in the severity of OSAHS between the two groups.
Patients with obstructive sleep apnea-hypopnea syndrome (OSAHS) often face poor asthma control.
A survey of 7,729 asthma patients found that up to 74% experienced nighttime coughing or wheezing at least once a week, 64% woke more than 3 times a week due to asthma attacks, and 40% woke at night due to asthma symptoms, indicating that poor nighttime asthma control is widespread.
Multiple studies have further clarified that OSAHS is an independent risk factor for poor asthma control.
A study evaluating 472 asthma patients found a significant association between OSAHS and poor asthma control, and this association was independent of other influencing factors such as obesity, gastroesophageal reflux, and nasal diseases.
Another questionnaire survey of 752 patients also showed a high incidence of OSAHS in asthma patients, regardless of whether their daytime symptoms were persistent or their nighttime symptoms were frequent.
Furthermore, research indicates that the prevalence of OSAHS can be as high as 95.5% in patients with unstable or refractory asthma. All this evidence collectively demonstrates a strong association between OSAHS and poor asthma control.
Causes of Asthma Attacks Due to OSAHS
1. Neuroreflex Factors
People with asthma already have more sensitive and strained airways than others.
If they also have OSAHS, the repeated sleep apnea during sleep acts like a series of stimuli to the airways, easily triggering or worsening asthma. The reasons are as follows:
1. Airway Disturbance: During sleep apnea, airflow is obstructed, and the body instinctively tries to inhale forcefully.
This creates a strong suction force in the chest cavity, pulling and stimulating the nerves in the airways, potentially causing airway constriction (spasm) and leading to wheezing.
2. Throat Vibration: Loud snoring and sleep apnea cause violent vibrations in the throat and glottis. This physical stimulation also triggers a nerve reflex, causing the bronchi to constrict.
3. Oxygen Deprivation: A direct consequence of sleep apnea is oxygen deficiency. Oxygen deficiency itself makes the airways more sensitive, and even minor stimuli can trigger asthma.
Simultaneously, the oxygen deficiency signal stimulates the “alarm” in the neck, causing the body to constrict the bronchi in a self-preservation response, which actually worsens asthma.
In simple terms, for asthma patients, the breathing interruptions, changes in intrathoracic pressure, and hypoxia caused by OSAHS are like repeatedly “provoking” the already sensitive airways at night, thus greatly increasing the risk of asthma attacks.
2. Gastroesophageal Reflux
Acid reflux during sleep is a significant cause of nocturnal asthma. When stomach acid refluxes into the esophagus, the acidic substance irritates the esophagus, potentially causing direct airway constriction and increased respiratory resistance.
It can also indirectly trigger asthma attacks through nerve reflexes. Therefore, actively treating acid reflux helps reduce nocturnal asthma attacks, lowers the risk of acute exacerbations, and improves the quality of life for asthma patients.
It is noteworthy that people with obstructive sleep apnea-hypopnea syndrome (OSAHS) are more prone to acid reflux than those who are simply obese or drink alcohol, with an incidence rate of approximately 58% to 62%.
This may be related to changes in intrathoracic pressure and impaired esophageal function during sleep apnea.
When OSAHS and gastroesophageal reflux coexist, they can influence each other, jointly leading to a significant worsening of nocturnal asthma symptoms.
3. Inflammation
OSAHS not only affects nighttime breathing but can also trigger or worsen asthma by inducing a persistent inflammatory response. This inflammation mainly includes the following two aspects:
First, locally in the airways, OSAHS patients have elevated levels of inflammatory factors (such as nitric oxide and interleukin-6).
These substances not only narrow the airway lumen and slow airflow but also make the airways more sensitive and prone to contraction upon stimulation, thus triggering asthma.
Second, OSAHS also causes systemic chronic inflammation, manifested by elevated levels of inflammatory markers such as C-reactive protein and tumor necrosis factor-α, which are correlated with the severity of OSAHS.
This systemic inflammation can further exacerbate the inflammatory state within the airways or directly stimulate airway smooth muscle contraction.
Furthermore, an increased number of neutrophils is frequently found in sputum examinations of OSAHS patients.
These types of inflammatory cells play an important role in the inflammatory process of non-eosinophilic asthma (especially some refractory asthma types), which also explains, from another perspective, that OSAHS may make asthma more difficult to control by promoting such inflammation.
4. Sleep Structure Disorder
For patients experiencing frequent nocturnal asthma attacks, sleep quality often deteriorates significantly.
Sleep monitoring data shows that these patients frequently wake up involuntarily during the night, have reduced overall effective sleep time, insufficient deep sleep, and exhibit disrupted and fragmented sleep structure.
These sleep problems, in turn, weaken the muscle tone and coordination in the throat during breathing, making the airway more prone to collapse or obstruction during sleep, thus inducing or worsening obstructive sleep apnea-hypopnea syndrome (OSAHS).
Compared to simple sleep deprivation, frequent interruptions in sleep structure (i.e., sleep fragmentation) have a more pronounced impact on nocturnal respiratory function.
This fragmented sleep state can lead to a significant increase in upper airway resistance, increasing its tendency to collapse and close during sleep
Therefore, sleep fragmentation caused by asthma further exacerbates airway instability and the risk of collapse, potentially worsening existing OSAHS and masking its typical clinical manifestations, ultimately making overall asthma control more difficult.
5. Obesity
Obesity is more than just weight gain; it affects your respiratory health in several ways, worsening asthma and sleep apnea:
1. Increased physical burden, making breathing more difficult: Excess fat, especially in the abdomen and chest, acts like a heavy “coat” constricting the chest, preventing the lungs from expanding fully and requiring more effort to breathe.
This “laborious breathing” state easily makes the already sensitive airways more strained and irritated.
2. Fat releases “inflammatory substances”: Fat tissue acts like a tireless “factory,” continuously producing substances called “inflammatory factors” (such as interleukin-6 and tumor necrosis factor-alpha).
These substances circulate throughout the body via the bloodstream, reaching your respiratory tract, where they exacerbate inflammation within the airways, directly triggering or making asthma symptoms more severe and frequent.
3. Causes and worsens sleep apnea: Obese individuals, especially those with thick necks and excess fat in the throat, are more prone to airway obstruction at night.
Repeated oxygen deprivation and sleep interruptions caused by sleep apnea can, in turn, stimulate the body to produce more inflammation, creating a vicious cycle of “obesity → sleep apnea → increased inflammation → worsening asthma.”
Simply put, controlling your weight not only reduces the burden on your body but also decreases the production of “inflammatory substances,” which helps stabilize your asthma condition and improves nighttime sleep breathing, breaking this mutually reinforcing cycle.
This is a crucial step in managing your overall health.
6. Abnormal Cardiac Function
Severe sleep apnea not only affects sleep but can also damage your heart, increasing the risk of heart failure, coronary heart disease, and other heart conditions.
This is because repeated pauses in breathing at night lead to intermittent oxygen deprivation and disrupted sleep structure.
Over time, this can damage blood vessel function, causing insufficient oxygen supply to the heart muscle, thus increasing the burden on the heart and potentially triggering or worsening heart failure.
Crucially, when heart function declines, it can also affect your breathing.
Studies show that poor heart function can make the airways abnormally sensitive, more prone to constriction in response to stimuli, leading to bronchospasm and airway hyperresponsiveness, often manifesting as nocturnal asthma attacks or exacerbations.
In short, this creates a vicious cycle: Sleep apnea → Increased burden on the heart → Triggering or worsening heart failure → Heart problems make the airways more sensitive → Triggering or worsening nocturnal asthma
Therefore, for patients with both asthma and suspected sleep apnea, actively assessing and treating OSAHS not only helps improve sleep and heart health but is also a crucial part of controlling nocturnal asthma.
7. Hormone Therapy
For asthma patients who need to use high-dose inhaled or even oral corticosteroids to control their condition, it is important to know that long-term use of these medications may increase the risk of developing sleep apnea.
Risk is dose-related. Studies have shown that compared to asthma patients who do not use inhaled corticosteroids, patients using small, medium, and large doses of inhaled corticosteroids have a progressively increasing risk of sleep apnea, approximately 2.3 times, 3.7 times, and 5.4 times higher, respectively.
This means that the higher the drug dose, the stronger the association with this risk.
There are two main reasons:
Changes in body shape: Long-term use of hormones may lead to fat accumulation around the torso and neck (central obesity, thickening of the neck), which physically narrows the upper airway.
Impact on muscle function: Especially oral hormones may affect the function of the muscles in the throat that maintain airway patency, making the airway more prone to collapse and blockage during sleep.
8. Nasal Diseases
Many asthma patients also suffer from allergic rhinitis or chronic sinusitis (commonly known as “sinusitis”).
In fact, examinations reveal that the vast majority of asthma patients have varying degrees of nasal inflammation. These nasal problems, such as nasal congestion and a runny nose, are not minor issues; they can create a chain reaction, affecting sleep and asthma control. The specific process is as follows:
Nasal congestion and difficulty breathing: When rhinitis or sinusitis causes nasal congestion, the resistance to airflow through the nasal cavity increases.
To inhale enough air, the body unconsciously forces itself to breathe, which causes the pressure deep in the throat to become lower than usual (similar to the feeling of forcefully sucking through a straw).
Inducing snoring and sleep apnea: This increased “suction” makes the already relaxed soft tissues of the throat more easily sucked together during sleep, causing vibration (snoring) or even complete collapse and blockage (sleep apnea), thus inducing or worsening obstructive sleep apnea-hypopnea syndrome (OSAHS).
Creating a vicious cycle: The oxygen deprivation and sleep interruption caused by sleep apnea, in turn, stimulate the body, making asthma more difficult to control and increasing the likelihood of nighttime symptoms.
The key good news is: this cycle can be broken!
Studies show that actively treating rhinitis and sinusitis (such as using nasal corticosteroids, nasal irrigation, and treating infections) can effectively reduce nasal congestion, thereby significantly improving breathing during sleep and reducing snoring and sleep apnea events. This is very helpful in improving overall asthma control.
Simply put, managing your nasal problems is not only about making breathing easier, but also a crucial part of improving nighttime sleep and helping control asthma.
Control and Treatment of OSAHS and Asthma
Sleep apnea and bronchial asthma often occur together and can exacerbate each other, making the other’s condition more difficult to control. Treatment of OSAHS and asthma usually interferes with each other.
Treating OSAHS can help control asthma: For patients with both conditions, nighttime asthma symptoms often significantly improve after using a CPAP machine to treat OSAHS.
This demonstrates that managing sleep apnea is a crucial part of asthma control.
Asthma medications may affect OSAHS: On the other hand, long-term basic asthma treatment (inhaled corticosteroids) requires special attention.
Studies have shown that using these medications, especially at higher doses, may increase the risk of developing or worsening OSAHS.
This may be due to changes in the local tissues of the throat that the medications may cause.
For patients who suffer from both asthma and OSAHS, CPAP is the core method for treating OSAHS and can effectively improve asthma control.
How does CPAP help with both conditions simultaneously?
1. Supporting the airway and stabilizing breathing: CPAP delivers gentle positive pressure airflow while you sleep, acting like an “invisible support” to open the throat and prevent airway collapse.
This directly addresses sleep apnea and hypoxia.
2. Reducing inflammation and allergies: Stabilizing breathing and improving hypoxia helps reduce systemic and airway inflammation levels, gradually calming oversensitive airways and reducing asthma attacks.
3. Reducing acid reflux: During sleep apnea, the dramatic rise and fall of the chest cavity can easily trigger acid reflux.
CPAP, by balancing chest pressure, can significantly reduce this reflux, preventing stomach acid from irritating the airway and esophagus, a major cause of nocturnal asthma.
What improvements can this treatment bring?
Studies have confirmed that consistent use of CPAP therapy can significantly reduce the frequency of nocturnal asthma symptoms and decrease the need for emergency bronchodilators (such as salbutamol inhaler), thereby improving overall quality of life.
