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