Effect of lung function on the apnea-hypopnea index in patients with overlap syndrome: a multicenter cross-sectional...

Patients with chronic obstructive pulmonary disease (COPD) and obstructive sleep apnea (OSA) are referred to as having overlap syndrome (OVS). However, the relationship of lung function with the apnea-hypopnea index (AHI) in patients with OVS has not been evaluated. This multicenter study aimed to evaluate the relationship.

COPD patients diagnosed by spirometry were recruited from four Chinese tertiary hospitals. Those patients were requested to attend an overnight polysomnography (PSG). The relationships between parameters of lung function and sleep respiration in patients with OVS were assessed using multiple regression analyses.

A total of 520 OVS patients and 246 patients with COPD only finally met inclusion criteria for study. After adjustment for age, sex, body mass index, neck circumference, economic status, smoking status, alcohol consumption, and hypertension, the forced expiratory volume in the first second (FEV₁) had a positive correlation with the AHI in patients with OVS (β, 0.17; 95% CI, 0.06-0.28; P < 0.01). However, when the severity of lung function of patients with OVS was stratified, the correlation with the FEV₁ of each grade and the AHI was absent (P > 0.05). Additionally, The FEV₁ was positively correlated with the nadir oxygen saturation (SaO₂) (β, 0.18; 95% CI, 0.08-0.27; P < 0.01) and was negatively correlated with the percentage of time spent with an SaO₂ below 90% (TS90%) (β,- 0.41; 95% CI,- 0.61-0.21; P < 0.01) in patients with OVS using multiple regression analyses.

Lung function was associated with the AHI in patients with OVS. The lower FEV₁ may play some protective role in the severity of AHI in OVS patients. Trial registry ClinicalTrials.gov , No.: NCT03182309, URL: www.clinicaltrials.gov .