Oral contraceptives and oestrogen replacement therapy as determinants of plasma fibrinogen level and fibrinolytic activity - The Northern Sweden MONICA study

Objective: To investigate the relationship between the use of oral contrace ptive pills (OC) or oestrogen replacement therapy (ORT), and haemostasis an d fibrinolysis. Design: Cross-sectional population study. Setting: Populati on screening in the Northern Sweden MONICA Study. Material: 775 women betwe en 25 and 64 years. Outcome measure: Plasma fibrinogen, tissue plasminogen activator (tPA) activity, tPA antigen and plasminogen activator inhibitor 1 (PAI-I) activity according to OC use in premenopausal and ORT use in postm enopausal women. Results: After adjusting for age, tPA antigen and PAI-1 ac tivity were significantly lower in OC users compared to nonusers. The diffe rences remained statistically significant after adjusting for anthropometri c and metabolic factors; tPA antigen levels were 26% lower and PAI-I activi ty was 39% lower in OC users. No difference between the groups was found in fibrinogen and tPA activity OR-T users had significantly lower age-adjuste d plasma fibrinogen and tPA antigen compared to the non-users. After adjust ing for smoking, anthropometric and metabolic factors, the values were stil l lower, but the differences were no longer statistically significant. tPA activity and PAI-1 activity did not differ between the groups. Conclusion: Users of OC showed a favourable pattern in haemostatic or fibrinolytic vari ables when compared to non-users. Users of ORT did not differ from non-user s in these variables after adjusting for possible confounders.