Associations of plasma fibrinogen and factor VII clotting activity with coronary heart disease and stroke: prospective cohort study from the screening phase of the Thrombosis Prevention Trial.

BACKGROUND: As with 'conventional' risk factors such as cholesterol and smoking, there is a need for large, long-term prospective studies on hemostatic factors. OBJECTIVES: To investigate the prospective relationship of fibrinogen and factor VII clotting activity (FVIIc) with risk of coronary heart disease (CHD) and stroke in a study with a large number of outcomes over a period of 15 years. PATIENTS/METHODS: A cohort of 22 715 men aged 45-69 years was screened for participation in the Thrombosis Prevention Trial. Men were followed up for fatal and non-fatal CHD and stroke events. There were 1515 CHD events (933 CHD deaths) and 391 strokes (180 stroke deaths). Hazard ratios (HRs) and 95% confidence intervals are expressed per standardized increase in log fibrinogen and log FVIIc, adjusting for age, trial treatment group, conventional CHD risk factors and regression dilution bias. RESULTS: Hazard ratios for fibrinogen were 1.52 (1.37-1.70) for all CHD events, and 1.36 (1.09-1.69) for all strokes. Exclusion of events within the first 10 years showed a persistent association between CHD and fibrinogen, with an adjusted HR of 1.93 (1.42-2.64). The HRs for FVIIc, adjusting for age and trial treatment, were 1.07 (1.01-1.12) for all CHD events and 1.07 (0.97-1.20) for all strokes, and the fully adjusted HRs were, respectively, 0.97 (0.84-1.05) and 1.07 (0.85-1.33). CONCLUSIONS: The persisting association between fibrinogen and CHD beyond 10 years may imply a causal effect. There is a small effect of FVIIc on CHD, after adjustment for age and trial treatment, but no association independent of other risk factors.