Cardiovascular disorders are common in patients with obstructive sleep apnoea syndrome (OSAS) but there is debate as to whether OSAS is an independent risk factor for their development, since OSAS may be associated with other disorders and risk factors that predispose to cardiovascular disease.
In an effort to quantify the risk of OSAS patients for cardiovascular disease arising from these other factors, the authors assessed the future risk for cardiovascular disease among a group of 114 consecutive patients with established OSAS prior to nasal continuous positive airway pressure therapy, using an established method of risk prediction employed in the Framingham studies.
Patients were 100 males, aged (mean±sd) 52±9.0 yrs, and 14 females, aged 51±10.4 yrs, with an apnoea/hypopnoea index of 45±22·h-1. Based on either a prior diagnosis, or a mean of three resting blood pressure recordings >140 mmHg systolic and/or 90 diastolic, 68% of patients were hypertensive. Only 18% were current smokers, while 16% had either diabetes mellitus or impaired glucose tolerance, and 63% had elevated fasting cholesterol and/or triglyceride levels. The estimated 10-yr risk of a coronary heart disease (CHD) event in males was (mean±sem) 13.9±0.9%, 95% confidence interval (95% CI) 12.1–16.0, and for a stroke was 12.3±1.4%; 95% CI 9.4–15.1, with a combined 10 yr risk for stroke and CHD events of 32.9±2.7%; 95% CI 27.8–38.5 in males aged >53 yrs.
These findings indicate that obstructive sleep apnoea syndrome patients are at high risk of future cardiovascular disease from factors other than obstructive sleep apnoea syndrome, and may help explain the difficulties in identifying a potential independent risk from obstructive sleep apnoea syndrome.