Obstructive sleep apnea (OSA) affects an estimated 15% of the population, of whom 80% are undiagnosed; the estimated annual economic burden of this disease in the United States is $150 billion. A study that was published online as part of the ATS 2020 International Conference examined the clinical value of spirometry to predict OSA diagnosis and severity.
The authors performed a retrospective chart review of diagnostic sleep studies performed at two hospitals between November 2017 and October 2018 (Canberra Hospital) and November 2017 and March 2018 (Prince of Wales Hospital). The associations between apnea-hypopnea index (AHI) and forced expiratory volume 1 percentage predicted (FEV1%) and forced vital capacity percentage predicted (FVC%) were analyzed using Spearman’s Rho test; FEV1% and FVC% were used as test variables in receiver operating characteristic (ROC) analysis.
Final analysis included 241 patients who received obstructive spirometry (n=46), restrictive spirometry (n=44), or normal spirometry (n=151). In the obstructive group, FEV1% (P=0.012) and FVC% (P=0.012) were significantly correlated with AHI. In normal and restrictive spirometry patients, no correlations were observed between AHI and FEV1% or FVC%. In the obstructive group, more than half of patients (n=25; 54.3%) were diagnosed with chronic obstructive pulmonary disease (COPD), and 20 patients (43.5%) were diagnosed with asthma. For FEV1%, the area under the ROC curve to identify moderate to severe OSA in obstructive spirometry patients was 0.710 (P=0.025); for FVC%, the value was 0.707 (P=0.027).
The study authors concluded that FEV1% and FVC% may be of use in identifying moderate to severe OSA in patients who have obstructive spirometry, noting that many of these patients had an asthma and/or COPD diagnosis.
“The interrelationship between airways disease and OSA requires further study. The negative correlation of FEV1% and FVC% with AHI suggests that there may be an association between the severity of airways disease and the severity of OSA,” they summarized.