Obstructive sleep apnoea and lung function, and their association with nocturnal hypoxemia: results from the Swedish CArdioPulmonary bioimage Study (SCAPIS) – a cross-sectional study

Abstract

Background OSA is highly prevalent and characterised by abnormal respiration during sleep. This large, population-based study aimed to investigate the associations between OSA and lung function in subjects aged 50–64 years.Method The population-based Swedish CArdioPulmonary bioimage Study includes information on anthropometry, comorbidities and spirometry. The current analysis included data from three centres (Gothenburg, Umeå and Uppsala) on whole-night respiratory polygraphy as a meta-analysis examining the overall effect size of lung function on sleep apnoea severity, expressed as ß-coefficient after stratifying for sex and adjusting for age, waist circumference and smoking status.Results Data from 9016 participants (54% women, age 58±4 years, body mass index 27±4 kg/m2) with sleep recordings of good quality were included in the final analysis. Forced expiratory volume during 1 s (FEV1) (ß=−0.10 (95% CI −0.16 to −0.03)), forced vital capacity (FVC) (−0.15 (−0.21 to −0.10)) and diffusion capacity for carbon monoxide (DLCO) (−0.08 (−0.10 to −0.05)) were all negatively associated with the oxygen desaturation index (ODI) and also with per cent of registration with nocturnal oxygen saturation <90% FVC (−0.44 (−0.87 to −0.01)), FEV1 (−0.86 (−1.36 to −0.36)) and DLCO (−0.47 (−0.60 to −0.35)). Additionally, a positive association was observed between FEV1 (0.13 (0.05 to 0.22)) and DLCO (0.07 (0.04 to 0.09)) with the mean nocturnal saturation. There was a negative association between DLCO and apnoea-hypopnoea index, AHI, (ß=−0.04 (95% CI−0.06 to −0.03)), while no associations were found between FEV1 or FVC and AHI.Conclusion In OSA, lower lung function is more distinctly associated with the nocturnal hypoxic burden than AHI. Potential lung function impairment should be investigated in OSA patients with a high ODI relative to AHI.