Smoking and oral contraceptive risks
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Cardiovascular Risks of Smoking and Oral Contraceptive Use
Smoking and oral contraceptive (OC) use both increase the risk of cardiovascular disease, but the combination of these two factors leads to a much higher risk, especially in women over 35 years old or those with certain genetic predispositions like the factor V Leiden mutation 1567. The main cardiovascular risk associated with OCs is thrombosis, and this risk is higher with higher estrogen doses and with certain progestins (like desogestrel and gestodene) 15. Studies consistently show that the risk of heart attack and stroke is much greater in women who both smoke and use OCs, with some research indicating that heavy smokers who use OCs have a risk of myocardial infarction up to 30 times higher than women with neither risk factor 25678.
Thromboembolic Events and Platelet Aggregation
Smoking and OC use together increase the risk of thromboembolic events, such as venous thrombosis and acute myocardial infarction, more than either factor alone 259. Smoking reduces protective prostacyclin levels and increases thromboxane, leading to greater platelet aggregation and clot formation in OC users . The risk of venous thrombosis is especially high in young women who smoke and use OCs, with an almost ninefold increase compared to non-smokers who do not use OCs .
Age and Dose Considerations
The absolute risk of fatal cardiovascular events in women under 35 is low, but it rises sharply with age, particularly in smokers who use OCs 56. For women over 35, the combination of smoking and OC use is associated with a much higher risk of cardiovascular death, and experts recommend that women in this age group who smoke should avoid estrogen-containing contraceptives 56. Lower estrogen doses in modern OCs have reduced, but not eliminated, these risks 125.
Impact on Menstrual Cycle Control
Smoking also affects menstrual cycle control in OC users, leading to a higher frequency of spotting and bleeding. Heavier smokers are more likely to experience these issues, which can lead to discontinuation of OCs and increased risk of unintended pregnancy .
Mortality and Public Health Perspective
While OC use alone does not increase overall mortality, smoking significantly increases the risk of death from all causes, including cardiovascular disease. The harmful effects of smoking are evident even in women aged 35–44, and the risk is much higher in those who smoke 15 or more cigarettes per day 456. From a public health perspective, eliminating smoking would have a much greater impact on reducing the risk of myocardial infarction and overall mortality than eliminating OC use 48.
Other Health Risks: Inflammatory Bowel Disease
Both smoking and OC use independently increase the risk of Crohn’s disease, but there is no evidence of a synergistic effect between the two for Crohn’s or ulcerative colitis .
Conclusion
The combination of smoking and oral contraceptive use greatly increases the risk of serious cardiovascular events, especially in women over 35. While modern low-dose OCs have reduced some risks, smoking remains the dominant factor in increasing cardiovascular and overall mortality. Women who smoke, particularly those over 35, should avoid estrogen-containing contraceptives and be encouraged to quit smoking to reduce their health risks.
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