Fibrinogen as a risk factor for coronary heart disease and mortality in middle-aged men and women - The Scottish Heart Health Study

Aims Fibrinogen was measured in 5095 men and 4860 men aged 40-59 in a random population sample from 25 districts of Scotland recruited during 1984-87: the Scottish Heart Health Study. Fibrinogen was then related to the chance of fatal and non-fatal coronary events and death from any cause during a subsequent follow-up period of around 8 years. Methods and results Fibrinogen was measured by the Clauss assay. The effect of fibrinogen on coronary heart disease and death was assessed through age-adjusted means and Cox proportional hazards regression models, accounting for age, cotinine (a measure of tobacco smoke inhalation) and 11 other major coronary risk factors. Fibrinogen was found to be an important risk factor for coronary heart disease in men and women, with and without pre-existing coronary heart disease. There appears to be a threshold effect, with those in the highest fifth of the distribution having a much increased risk. Estimated age-adjusted hazard ratios by sex and pre-existing coronary heart disease group for the highest to lowest fifth of fibrinogen range between 1.93 and 4.86. Fibrinogen is also important as a risk factor for coronary death and all-causes mortality, with a similar threshold effect. Comparing the two extreme fifths, the hazard ratios for coronary death are 3.01 and 3.42, and for all-cause mortality are 2.59 and 2.20, for men and women respectively. Adjustment for cotinine reduces the hazard ratios, but further adjustment for the other 11 risk factors has little effect for coronary heart disease events. After full adjustment there is a remaining significant (P<0.05) hazard ratio for coronary death and death from any cause and for a coronary heart disease event for those free of coronary heart disease at baseline, amongst men, comparing the highest to the lowest fifth. Conclusion Fibrinogen is a strong predictor of coronary heart disease, fatal or non-fatal, new or recurrent, and of death from an unspecified cause, for both men and women. Its effect is only partially attributable to other coronary risk factors, the most important of which is smoking.