Obstructive Sleep Apnea Screened by Overnight Pulse Oximetry and Higher Risk of Serious Cardiovascular Events: Prospective Cohort Study in the Primary Care

Abstract

Introduction: Obstructive sleep apnea (OSA) is a condition characterized by sleep disordered breathing which results in health impairment and other related injuries. Cardiovascular and neurocognitive morbidities and increased risk of motor vehicle accidents have been demonstrated in patients with untreated OSA. Overnight pulse oximetry is a good screening tool for OSA. There is no study to examine the prospective outcome of patients with screening positive OSA in the primary care setting. Methodology: This is a prospective cohort study involving consecutive patients whom had performed OSA screening by overnight pulse oximetry in a primary care clinic of Hong Kong from year 2011 to year 2012. One hundred and eighty consecutive OSA screening positive patients were the cohort group while 180 consecutive OSA screening negative patients were the control group. The five year incidence of serious cardiovascular complications and associated predictive factors were examined. Results: Both of cohort and control group patients were followed prospectively for 5 years. There was higher proportion of male (68.3% versus 45.0%, p<0.001) and obesity (58.3% versus 41.1%, p=0.001) patients in the cohort group. There was no statistical difference in concomitant chronic disease or difference in mean blood pressure and Epworth Sleepiness Scale (ESS) score among two groups. At five year follow up, there was no cardiovascular related mortality among two groups. The five year relative risk (RR) of screening positive OSA versus screening negative for serious cardiovascular event is 3.03 (95% CI, 1.16-7.86; p=0.018). By stratification, the relative risk for stroke is 1.69 (95% CI, 0.40-7.16; p=0.475), while for coronary artery disease (CAD) is 4.24 (95%CI, 1.18-15.29; p=0.017). Conclusion: Overnight pulse oximetry screening positive obstructive sleep apnea is the independent risk factor for coronary artery disease.