Severe OSA linked to poorer lung function over time
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Key takeaways:
- Patients with high apnea-hypopnea index scores had more high attenuation areas on CT and lower measures of lung function over time.
- Belonging to the highest hypoxic burden quartile also led to these outcomes.
Over time, adults with severe obstructive sleep apnea had more high attenuation areas on CT and lower lung function, which may signal early interstitial lung disease, according to data published in Annals of the American Thoracic Society.
“There has been ongoing interest as to whether sleep-disordered breathing, which includes OSA, may have a harmful effect on the lungs and particularly in pulmonary fibrosis,” John S. Kim, MD, MS, of the division of pulmonary and critical care medicine at University of Virginia School of Medicine, told Healio. “Prior work has suggested increased adiposity may confound the association between OSA severity and lung imaging abnormalities and function. However, in our study we observed that the relationship between sleep apnea severity and these imaging markers of possible lung inflammation and fibrosis were persistent after accounting for body habitus.”
Kim and colleagues evaluated 784 older community dwelling adults (median age, 67 years; 54% women) from the Multi-Ethnic Study of Atherosclerosis (MESA) to determine whether there is a relationship between OSA severity and worse lung function over time using linear mixed effects models with random intercept that accounted for age, sex, smoking history, height and weight.
These patients had an apnea-hypopnea index (AHI) measurement, high attenuation areas ranging from –600 to –250 Hounsfield units and full-lung CT scans, and 677 adults also had spirometry assessments, which researchers evaluated to see if lung volume and FVC were linked to OSA severity.
Of the total cohort, 249 adults (38% women; BMI, 31 kg/m2) had an AHI of 15 events or more per hour, whereas 254 adults (53% women; BMI, 29 kg/m2) experienced five to less than 15 events per hour and 281 adults (69% women, 27 kg/m2) experienced less than five events per hour.
Among those in the group with the most severe measures of AHI, researchers found that every 10 years high attenuation areas increased by 11.3% (95% CI, 3.74%-19.35%) compared with adults with less than five events per hour.
When researchers evenly divided the cohort into quartiles of hypoxic burden, those in the highest quartile showed a 9.85% (95% CI, 1.4%-19.01%) rise in high attenuation areas per 10 years vs. the lowest hypoxic burden quartile.
In terms of lung function, adults in the highest AHI category (n = 220) also demonstrated a greater reduction in total lung volume than adults in the lowest AHI category (n = 229), with a 220.2 mL decrease (95% CI, –392.5 to –47.8) per 10 years. Researchers found a comparable result among adults in the highest vs. lowest hypoxic burden quartile, with a 308 mL decrease (95% CI, –504 to –112) in total lung volume imaged every 10 years.
Compared with those with an AHI of less than five events per hour, FVC decreased by 3.63% (95% CI, –6.83% to –0.43%) every 10 years among those with an AHI of 15 events or more per hour. Although adults in the highest vs. lowest hypoxic burden quartile had a greater decrease in FVC, the difference between the two groups was not significant.
Similar to the highest AHI quartile, researchers found an increase in high attenuation areas and decreases in total lung volume and FVC among adults in the highest oxygen desaturation index (ODI) quartile.
In interactions between high attenuation areas and total lung volume with polysomnography measures, BMI did not change these relationships; however, a BMI lower than 30 kg/m2 contributed to a stronger relationship between hypoxic burden and ODI with FVC, according to researchers.
Of the 1,148 adults who underwent interstitial lung abnormality (ILA) testing, 128 adults had an abnormality.
Notably, mortality was highest among adults with ILA in the group with the most AHI events per hour (18.8 per 1,000 person-years).
“While this study may not directly impact clinicians, it raises important questions of how sleep-disordered breathing may impact respiratory health,” Kim told Healio. “It is plausible that frequent drops in oxygen levels at night, the physical effects on the lung from breathing with an airway that is obstructed and that these events can occur very frequently during sleep may be harmful to the lungs.
“It remains unknown whether effective treatment for OSA can have a beneficial impact on the lungs and reduce the risk of development or progression of pulmonary fibrosis,” Kim added. “Alternatively, treatments for sleep apnea may actually be harmful to these patients as prospective and intervention studies are needed to answer this.”