Obstructive sleep apnoea and cardiovascular events in a Chinese cohort

Introduction: Although several clinical and epidemiological studies have reported an association between obstructive sleep apnoea (OSA) and cardiovascular (CV) events, the results remain inconsistent. We evaluated the role of OSA on the incidence of CV events in a Chinese cohort. Methods: The eligible cohort was drawn from those who received sleep studies between 01/01/2006 and 31/12/2010 in the Department of Medicine, Queen Mary Hospital. Follow-up data were drawn from the Hospital Authority Clinical Management System up to the day of data entry in this study. Apnoea-hypopnea index (AHI) from automated scoring of polysomnogram was used in the Cox regression model, controlling for age, gender, body mass index(BMI), daytime sleepiness, prior diabetes, hypertension and atrial fibrillation. Composite CV events were defined by the first hospitalisation of myocardial infarction, revascularisation procedures or exacerbation of congestive heart failure after the date of PSG. Results: 84 (7.2%) of 1159 subjects experienced CV events over a median follow-up of 7.3 years, giving an incident rate around 1.03 per 100 person-years. In both univariate and multivariate models, there were no significant association between AHI and CV events. On the other hand, BMI as an indicator of obesity was an independent and significant predictor of CV events. This analysis has not yet taken into account the effect of treatment intervention for OSA and possible deviation with use of manually scored sleep data. Conclusion: OSA per se, independent of obesity, did not predict CV outcomes of coronary heart disease and heart failure. Further investigation of the modifying effects of OSA treatment on this outcome is needed.