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Centre for Evidence-
Based Medicine

Cardiovascular Disease - Oral contraceptive may increase risk

Clinical Bottom Line

Increased risk of stroke in patients taking OCs. Lower dose pills are now in common use and may be safer than the higher dose pills examined in this study. Even with the older higher dosages, the absolute risks of ischaemic stroke in OC users are low; 5880 women would need to take OCs for 1 year to cause 1 additional stroke.

Citation

Mant J, Painter R, Vessey M. Risk of myocardial infarction, angina and stroke in users of oral contraceptives: an updated analysis of a cohort study. Br J Obstet Gynaecol 1998;105:890-6.

Clinical Question

What is the association between oral contraceptive use in women and the risk for cardiovascular disease?

Search Terms

PubMed was searched using the terms "oral contracept*" AND "cardiovascular disease" AND "risk factor*" AND "cohort stud*" AND "prospective".

The Study

17,032 women aged 25 to 39 years were recruited between 1968 and 1974 from 17 family planning clinics in England and Scotland. They provided information annually about contraception method. 15,292 (90%) were still participating at age 45. Women were categorised in terms of OC use. Hospital-confirmed diagnoses of cardiovascular events (myocardial infarction, angina, ischaemic stroke, subarachnoid haemorrhage, intracerebral haemorrhage, and transient ischaemic attack) were recorded.

The Evidence

Outcome Relative Risk* 95% Confidence Interval
MI 1.5 0.6 to 3.2
Angina 0.5 0.1 to 1.4
Ischaemic Stroke 2.9 1.3 to 6.7
* Adjusted for age, parity, social class, smoking, comorbidity

Comments

Risk of MI was significantly increased in heavy smokers who used OC compared with non-users

Appraised By

Alba DiCenso, RN, PhD.
School of Nursing
McMaster University, Hamilton, Ontario, Canada.
Fax: (905) 546-0401
Email: dicensoa@fhs.mcmaster.ca
Appraised February 1999.

Expiry Date

2000