Associations of haemostatic variables with body mass index: a community-based study.

Obesity is a risk factor for venous and arterial thrombosis. We examined relationships between body mass index (BMI) and a number of haemostatic and inflammatory variables in a community-based study of 150 adults (73 male, 77 female; age range, 23-80 years). Associations with BMI were sought after adjustment for age, smoking and diurnal variation. There were significant interactions of gender on the associations of BMI with fibrinogen (P = 0.002) and C-reactive protein (P = 0.02). In women, there were strong positive associations of BMI with fibrinogen (r = 0.57, P < 0.0001) and C-reactive protein (r = 0.40, P = 0.001). In men, these associations were non-significantly inverse. For all other variables there were no sex differences, so results for men and women were combined. Significant positive associations with BMI were seen for factor VIIc, activated factor XII, antithrombin activity, protein C activity and plasminogen activator inhibitor-1 activity. Inverse associations with BMI were seen for tissue plasminogen activator activity and activated protein C ratio. Increasing BMI is associated with elevation of certain coagulation factors, inhibitors of fibrinolysis, and inhibitors of coagulation, the latter potentially reflecting a compensatory response. Gender influences the association of certain inflammatory variables with BMI so the sexes should be considered separately in studies of inflammation and obesity.