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

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 ( r (2)=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 (Delta r (2)=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.