Authors (including presenting author) :
Chiang LK, Kam CW, Ng VL
Affiliation :
Dept. of Family Medicine & General Outpatient Clinics (GOPCs), Kowloon Central Cluster (KCC)
Introduction :
Obstructive sleep apnea (OSA) is a condition characterized by disordered breathing during sleep which results in health impairment and other related injuries. Cardiovascular and neurocognitive morbidities and increased risk of motor vehicle accidents have been demonstrated in untreated OSA.
Objectives :
1. To investigate the five year incident of overnight pulse oximetry screened obstructive sleep apnea related stroke and coronary artery disease;
2. To examine the predictive correlation between overnight pulse oximetry screened obstructive sleep apnea and cardiovascular complications.
Methodology :
This is a prospective cohort study involving consecutive patients who had performed OSA screening by overnight pulse oximetry (OPO) in a primary care clinic from 1/1/2010 to 31/12/2011. Portable OPO was used for OSA screening, which measured and stored pulse rate and SpO2 value continuously. Oxygen desaturation was defined as a decrease of ≧4% from baseline SpO2. Subjects who had sleep disordered breathing events associated with 5 or more oxygen desaturation events of the peripheral artery of 4% or greater per hour (ODI_4 ≧5 events/hr) was defined as screening positive. Consecutive OSA screening postive and negative patients were allocated to cohort group and control group respectively. The five year incidence of serious cardiovascular complications and associated predictive factors were examined. Logistic regression modelling was used to estimate the effect of OSA on the incidence of CVD events before and after adjustment for other risk factors.
Result & Outcome :
180 cohort and 180 control 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 between two groups. At five year follow up, there was no cardiovascular related mortality among two groups. 17 events (incidence 9.44%) of significant cardiovascular complication occurred at cohort group, including 5 cases of ischaemic stroke, 7 cases of acute myocardial infarction (AMI) and 5 cases of ischaemic heart disease. 6 events (3.33%) of cardiovascular complications, including 3 cases of stroke and 3 cases of AMI occurred in the control group. The five year relative risk (RR) of screening positive OSA 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), and 4.24 (95%CI, 1.18-15.29; p=0.017) for coronary artery disease (CAD). In conclusion, OPO screening positive OSA is an independent risk factor for serious cardiovascular diseases. Well-structured management protocol for screening positive OSA patients and associated cardiovascular risk interventions should be formulated and implemented in the primary care setting.
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