Smoking is a known risk factor for dozens of diseases, but its relationship with obstructive sleep apnea has remained surprisingly understudied. A new study published in Scientific Reports provides some of the strongest evidence yet that smoking — and even a history of past smoking — significantly worsens sleep apnea severity.
Researchers from the Study of Health in Pomerania (SHIP), a large population-based cohort in northern Germany, analyzed 1,206 adults who underwent complete overnight polysomnography alongside detailed smoking assessments. Unlike many previous studies that relied on questionnaires or home sleep tests, this research used the gold-standard laboratory sleep study to objectively measure breathing interruptions during sleep.
The Numbers
Current smokers had 75% greater odds of more severe sleep apnea compared to people who had never smoked (odds ratio 1.75, 95% CI 1.27–2.41, P<.001). The measure used was the apnea-hypopnea index (AHI), the standard clinical metric that counts the number of breathing pauses and shallow breaths per hour of sleep.
What caught the researchers' attention was the finding for former smokers: they showed virtually identical elevation in risk, with 76% greater odds of higher AHI severity compared to never-smokers (OR 1.76, 95% CI 1.27–2.43, P<.001).
Stratified analyses confirmed these effects held across both younger and older age groups, suggesting the association is not simply a product of age-related airway changes.
Why Quitting Doesn't Fully Reverse the Damage
The persistent risk in former smokers points to structural changes in the upper airway that do not fully resolve after smoking cessation. Decades of research have documented several mechanisms through which smoking damages the tissues that keep the airway open during sleep:
- Chronic inflammation: Cigarette smoke triggers persistent inflammation in the pharyngeal mucosa — the soft tissue lining the throat — causing swelling that narrows the airway
- Mucosal edema: Fluid accumulation in the upper airway tissues further reduces the available space for airflow
- Impaired neuromuscular reflexes: Nicotine and other toxins may damage the nerve endings that sense airway collapse and trigger the protective muscle contractions that reopen the airway during sleep
- Structural remodeling: Long-term exposure can permanently alter the collagen and elastic fiber composition of upper airway tissues, reducing their ability to resist collapse
While some of these changes — particularly acute inflammation and edema — improve after quitting, the structural remodeling and potential nerve damage may persist for years or indefinitely.
An Overlooked Factor in Sleep Apnea Screening
The findings have practical implications for clinical screening. Current sleep apnea risk calculators heavily weight factors like body mass index, neck circumference, age, and sex. Smoking history is not a prominent component of the most widely used screening tools, including the STOP-Bang questionnaire.
The Pomerania data suggest that clinicians should be asking about both current and past smoking when evaluating sleep apnea risk. A former smoker who quit 10 years ago and has a borderline BMI may carry more apnea risk than screening tools currently estimate.
This is particularly relevant given the high prevalence of both conditions. An estimated 936 million people worldwide have obstructive sleep apnea, and approximately 1.3 billion people use tobacco globally. The overlap between these populations is substantial, yet the connection remains underappreciated in primary care settings.
The Compounding Effect
Sleep apnea and smoking share many of the same downstream consequences — cardiovascular disease, systemic inflammation, and metabolic dysfunction. When both are present, the effects may compound rather than simply add.
A patient with moderate sleep apnea who also smokes faces cumulative oxidative stress during sleep: each apnea event drops blood oxygen levels, while the residual effects of smoking impair the body's ability to respond to and recover from those oxygen dips. This combination may accelerate the development of hypertension, atrial fibrillation, and stroke risk beyond what either condition would produce alone.
What This Means for Patients
If you smoke and have symptoms of sleep apnea — loud snoring, witnessed breathing pauses during sleep, excessive daytime sleepiness, or morning headaches — the urgency of seeking evaluation is heightened. Smoking may be making your apnea worse than your weight or anatomy alone would predict.
If you are a former smoker, do not assume that quitting eliminated your risk. The airway changes from years of smoking may persist, and a sleep evaluation may still be warranted if symptoms are present.
For patients already diagnosed with sleep apnea, quitting smoking remains one of the most impactful lifestyle changes available — even if it does not fully reverse the AHI elevation, it reduces the cardiovascular burden that makes apnea dangerous.
The full study is available in Scientific Reports.
