Repeat MI and Stroke Risks Defined in 'Younger' Women on Oral Contraceptives

Veronica Hackethal

December 01, 2015

LEIDEN, THE NETHERLANDS — Women who have had a cardiovascular event while on oral contraceptives have a substantially higher long-term risk of ischemic stroke and MI compared with healthy women, according to a Dutch study published online on November 23, 2015 in JAMA Internal Medicine[1]. The analysis is based on a cohort of adult women who were aged 50 and younger at baseline.

"The risk can be seen as true to type, which means those women who experience a cardiovascular event are much more likely to have the same type of event than a different type," coauthor Dr Bob Siegerink (Center for Stroke Research, Berlin, Germany) commented to heartwire from Medscape.

The results highlight the negative consequences of cardiovascular events in young women that continue for decades, pointing to the need for lifelong prevention strategies.

"Women who initially had a myocardial infarction are much more likely to develop a second MI than a stroke," he explained, "This is an indicator that the mechanisms leading to the increased cardiovascular risk in these women is disease specific. Future studies will help us see if the recurrence mechanisms in these subtypes are also different, possibly leading to more tailored treatments in the future."

In the study, researchers drew on data from the Risk of Arterial Thrombosis in Relation to Oral Contraceptives (RATIO) study. It included female survivors aged 18 to 50 who had had a first MI or ischemic stroke between January 1995 and December 1998. The control group included women without a history of arterial thrombosis. Researchers followed women until December 2012 (mean of 18.7 years). They used data from Dutch registries to determine cause of death and hospital admissions and adjusted results for age, lifestyle, disease, and family history of cardiovascular events.

The analysis included 226 women with MI, 160 with ischemic stroke, and 782 controls (mean ages 42.4, 40.0, and 48.4 years, respectively).

Among women with MI, mortality rates were about 3.7 times higher (8.8 per 1000 person-years, 95% CI 6.2–12.3) than controls (2.4 per 1000 person-years, 95% CI 1.7–3.4). Among women with ischemic stroke, mortality rates were about 1.8 times higher than controls (4.4 per 1000 person-years, 95% CI 2.4–7.6).

The higher rates of mortality continued over time, mainly due to a high rate of deaths from acute vascular events.

Women who had experienced an MI had higher rates of cardiac events (10.1 per 1000 person-years, 95% CI 7.5–13.8) than cerebral events (1.9 per 1000 person-years, 95% CI 0.8–3.8).

Conversely, women who had experienced ischemic stroke had higher rates of cerebral events (11.1 per 1000 person-years, 95% CI 7.5–15.9) than cardiac events (2.7 per 1000 person-years, 95% CI 1.2–5.4).

Even though the relative risks are "quite substantial," the results need to be put into perspective by considering the absolute risks, Siegerink pointed out.

"After all, after almost 20 years of follow-up, the majority of the women were still alive—90% for ischemic stroke and 80% for myocardial infarction," he explained.

To reduce the risk of recurrence in patients like these, clinicians should address the risk factors that played a role in the disease, he continued.

"These results, as well as the results from other studies, indicate that it is important to try to keep the cardiovascular burden in these young patients as low as possible through secondary prevention and lifestyle changes," Siegerink stressed, "In this case, that [also] means that women who suffered from ischemic stroke or myocardial infarction should reconsider their [oral contraception] use and perhaps search for alternative ways of anticonception."

This study was funded by a grant from the Den Dulk Moermans Fonds and was also financially supported by the Fondazione Angelo Bianchi Bonomi. The authors report no relevant financial relationships.

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