Is there a relationship between asthma and obstructive sleep apnea (OSA)?

Relationship Between Asthma and Obstructive Sleep Apnea

Yes, there is a significant bidirectional relationship between asthma and obstructive sleep apnea (OSA), with asthma patients having 2.5 times higher risk of developing OSA, and OSA worsening asthma control and lung function, particularly in children. 1, 2

Epidemiological Evidence

The association between these conditions is substantial and goes beyond chance coexistence:

• Approximately 50% of asthmatic patients have comorbid OSA, with the adjusted risk being 2.5 times higher than in non-asthmatic individuals 3
• More severe or difficult-to-control asthma is independently associated with OSA (OR = 4.36), meaning patients with poorly controlled asthma have over 4-fold increased odds of having OSA 2
• The prevalence of OSA increases proportionally with asthma severity 1, 2

Pathophysiological Mechanisms Linking the Two Conditions

Direct Mechanistic Links

Corticosteroid-induced weight gain represents a critical pathway where asthma treatment directly increases OSA risk, as systemic corticosteroids used for refractory asthma often lead to obesity, the principal risk factor for OSA 4, 1

Upper airway effects of inhaled corticosteroids may generate myopathy in pharyngeal muscles through local deposition, similar to vocal cord effects causing dysphonia, potentially increasing pharyngeal collapsibility 3

Mechanical effects and inflammation create bidirectional pathways, with intermittent hypoxia from OSA potentially worsening airway inflammation, while asthmatic airway inflammation may increase pharyngeal collapsibility 1, 5

Shared Risk Factors

Both conditions share multiple aggravating factors including:

• Obesity (present in 60-90% of OSA patients) 6
• Gastroesophageal reflux disease 4, 5
• Rhinitis and nasal obstruction 4, 1
• Systemic inflammation 7

Clinical Impact on Disease Severity

OSA's Effect on Asthma

OSA significantly worsens lung function in asthmatic patients, particularly in children where the effect on forced expiratory volume (FEV1) is statistically significant 2. In adults, the trend toward decreased FEV1 exists but requires further confirmation 2.

Coexisting asthma and OSA produce worse outcomes than either condition alone, including:

• Poorer sleep quality with increased N1 and N2 sleep stages and decreased REM sleep 7
• More profound nocturnal hypoxemia (mean oxygen saturation 93.4% vs 94.7% in OSA alone) 7
• Higher systemic inflammation markers (elevated CRP and IL-6) 7
• Increased frequency of asthma exacerbations 8

Asthma's Effect on OSA

Asthma increases daytime sleepiness in OSA patients as measured by the Epworth Sleepiness Scale (WMD = 0.60) 2

Asthma may lower the arousal threshold in OSA, potentially resulting in the hypopnea-with-arousal phenotype rather than complete apneas 8

Clinical Screening Recommendations

When to Screen Asthma Patients for OSA

Screen all patients with moderate-to-severe or difficult-to-control asthma for OSA, particularly those who are overweight or obese 4, 1, 2

Specific indicators requiring OSA evaluation in asthmatic patients:

• Frequent nighttime asthma symptoms despite treatment 4
• Significant weight gain, especially in those on systemic corticosteroids 4
• Complaints of loud snoring, poor quality sleep, or excessive daytime sleepiness 4
• Unexplained worsening of asthma control 1

When to Screen OSA Patients for Asthma

Evaluate OSA patients for asthma when they present with:

• Nocturnal respiratory symptoms beyond typical OSA presentation 4
• Wheezing or variable airflow obstruction 4
• History of atopy or allergic rhinitis 4

Pulmonary function testing should be performed in patients with rhinitis and OSA symptoms to assess for coexisting asthma 4

Pediatric Considerations

Formal evaluation for OSA should be considered in children with chronic rhinitis and other sleep-disordered breathing risk factors, as rhinitis is a strong predictor of habitual snoring in children 4, 1

Diagnostic Approach

Polysomnography remains the gold standard for diagnosing OSA in asthmatic patients 1. Home sleep studies may have higher false-negative rates and should be interpreted cautiously in this population 4.

Important caveat: OSA presents many similar features to nocturnal asthma, and some scholars have termed the coexistence as "alternative overlap syndrome" 5. Accurate diagnosis is essential because CPAP treatment may disrupt sleep in asthma patients who do not actually have OSA 4.

Treatment Implications

Managing Comorbid Conditions

Weight management is crucial for patients with both conditions or at risk for OSA, as it addresses the primary modifiable risk factor 1, 6

Treatment of nasal obstruction and rhinitis may improve both conditions:

• Intranasal corticosteroids reduce nasal airway resistance and apnea-hypopnea frequency in patients with both OSA and rhinitis 4, 1
• In OSA patients with ragweed allergy, apnea-hypopnea episodes were more frequent during symptomatic periods with increased nasal resistance 4

Gastroesophageal reflux treatment should be considered, particularly in patients with frequent nighttime symptoms, using proton pump inhibitors and lifestyle modifications 4

Medication Considerations

Exercise caution with inhaled corticosteroid technique in patients with OSA, as pharyngeal deposition may contribute to upper airway muscle dysfunction 3

Consider ultrafine particle formulations with less pharyngeal deposition when treating asthma in OSA patients 3

CPAP Therapy Effects

Treatment of OSA with CPAP may improve asthma symptoms in patients with both conditions, though the evidence is primarily observational 4, 5. Randomized controlled trials are needed to definitively establish this benefit while controlling for confounding factors 8.

Common Pitfalls to Avoid

Do not assume OSA is absent in normal-weight asthmatic patients, as obesity is not required for OSA development, particularly in older adults 6

Do not attribute all nocturnal respiratory symptoms to asthma alone in patients with risk factors for OSA, as this leads to underdiagnosis and inadequate treatment of both conditions 4, 1

Do not overlook systemic corticosteroid-induced weight gain as a modifiable risk factor for OSA development in asthma patients requiring step 6 care 4, 1

Recognize that treatment of one condition may improve the other, making comprehensive evaluation and management of both conditions essential for optimal outcomes 1, 5