Independent contribution of psychological factors to fibrin turnover in subjects with sleep apnoea and/or systemic hypertension

Abstract

By promoting atherosclerosis and thrombosis, a blood-clotting diathesis could contribute to excess cardiovascular morbidity and mortality in patients with systemic hypertension and/or obstructive sleep apnoea. Since psychological states affect haemostatic activity, we wondered about the contribution of behavioural factors to a hypercoagulable state in subjects with increased risk of cardiovascular disease. To tease apart the potential additive nature of cardiovascular disease risk, we examined four patient groups–hypertensives and normotensives, with and without sleep apnoea. The procoagulant molecules thrombin–antithrombin III complex, fibrin D-dimer and von Willebrand factor antigen were measured in 88 subjects (mean age 47 years; range 32–64 years) who underwent full polysomnography. Subjects completed the Center for Epidemiological Studies–Depression (CES-D) Scale, the Cook–Medley (CM) Hostility Scale, and the Profile of Mood States (POMS). Sleep apnoea, hypertension status, age, body mass index and psychological variables (CES-D, CM Stress, and POMS Vigour–Activity) together explained 29% of the variance in D-dimer, a marker of fibrin turnover (r2 = 0.29, P = 0.001). CES-D, CM Stress and POMS Vigour–Activity explained 17% of this variance even after controlling for sleep apnoea, hypertension status, age and body mass index (Δr2 = 0.17, P = 0.001). Thrombin–antithrombin III complex and von Willebrand factor were not significantly related to psychological variables, but this may reflect limited statistical power. Thus psychological factors are independently associated with D-dimer and explain as much of its variance as do traditional correlates (hypertension, sleep apnoea, age and body mass index). These results may provide a rationale for linking behavioural aspects with cardiovascular events.