Circulating cardiovascular risk factors in obstructive sleep apnoea: data from randomised controlled trials


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Abstract

Background:Obstructive sleep apnoea (OSA) is associated with high cardiovascular morbidity and mortality and is an independent risk factor for hypertension. Novel circulating cardiovascular risk markers enabling a more accurate prediction of cardiovascular risk have been identified. Examination of these markers may clarify the increased risk in OSA and contribute to an analysis of the benefits of treatment.Methods:Plasma levels of total cholesterol and triglyceride and activated coagulation factors XIIa and VIIa, factors VII, VIII, XII, fibrinogen, thrombin-antithrombin (TAT), von Willebrand factor antigen (vWFAg), soluble P-selectin (sP-sel), and homocysteine were measured before and after treatment for 1 month with therapeutic or subtherapeutic (control) continuous positive airways pressure (CPAP) in 220 patients with OSA.Results:Levels of activated coagulation factors XIIa, VIIa, TAT and sP-sel were higher in OSA patients at baseline than in unmatched controls, but did not fall with 1 month of therapeutic CPAP treatment. The raised sP-sel levels correlated only with body mass index (p = 0.002). There was a trend towards a significant fall in total cholesterol with therapeutic CPAP (p = 0.06) compared with the control group. In the therapeutic group there was a clinically significant mean fall in total cholesterol of 0.28 mmol/l (95% confidence interval 0.11 to 0.45, p = 0.001) which may reduce cardiovascular risk by about 15%.Conclusion:A number of activated coagulation factors are increased in untreated OSA patients, potentially contributing to vascular risk, but they do not fall with 1 month of CPAP treatment. Nasal CPAP may produce a clinically relevant fall in total cholesterol level, potentially reducing cardiovascular risk, but this needs to be verified in a larger prospective study.

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