Should women take aspirin to prevent cardiovascular disease?

The following questions and answers summarize cases discussed in the January 2009 issue of Menopause e-Consult, a newsletter of the North American Menopause Society (NAMS).

Who should take aspirin to prevent cardiovascular disease?

Which women should take aspirin for primary prevention of cardiovascular disease (CVD)? What factors should you consider when deciding whether to recommend the drug?¹

The WHS followed 39,876 initially healthy women 45 years and older for 10 years to evaluate the benefits and risks of low-dose aspirin (100 mg on alternate days) for preventing major cardiovascular events-MI, stroke, and cardiovascular death.³ The trial showed a statistically nonsignificant overall reduction of 9% in major cardiovascular events but found that aspirin significantly lowered the risk of total stroke by 17% (95% CI; 1%–31%) and ischemic stroke by 24% (95% CI; 7%–37%). Aspirin didn't decrease the risk of MI or cardiovascular death, however.

As expected, aspirin increased bleeding risks: Gastrointestinal hemorrhages necessitating transfusion occurred 40% more often with aspirin, and the risk of hemorrhagic stroke increased a nonsignificant 24%.

Age seemed to be a major determinant of cardiovascular response to aspirin and the benefit-risk ratio of therapy.³ WHS participants older than age 65 showed clear benefit from aspirin; women younger than 65 experienced little or no protection. Women older than 65 taking aspirin had fewer major CVD events but more gastrointestinal hemorrhages requiring transfusion. Women younger than 65 showed no decrease in major CVD events but had a similar increase in gastrointestinal bleeding-resulting in a net adverse effect and unfavorable benefit/risk ratio. Age predicted benefit-risk ratio more strongly than Framingham Risk Score (few of the women had high 10-year coronary risks).

RECOMMENDATIONS

For primary prevention of CVD, meta-analyses suggest that aspirin significantly decreases the risk of MI but not stroke in men and stroke but not MI in women.³ Aspirin doesn't reduce major CVD events in women younger than 65 years, but it does decrease MI, stroke, and composite CVD events in women older than 65. Low-dose aspirin (81 mg–100 mg per day) should be considered, unless contraindicated, for women 65 years and older, who will likely derive a net benefit. Patients with diabetes or established CVD may need higher doses.

For most women younger than 65 years, the risks of aspirin may outweigh the benefits. It isn't known whether aspirin may benefit younger women at risk of CVD or whether higher doses are needed to protect the heart. The available evidence doesn't support using aspirin routinely for primary prevention in women younger than 65 unless they have a high coronary risk score (high 10-year risk by the Framingham or Reynold's Risk Score) or diabetes. This is also the position of the American Heart Association.⁶

JOANN E. MANSON, MD, DRPH, is Professor of Medicine and Elizabeth Fay Brigham Professor of Women's Health, Harvard Medical School, and Chief of Preventive Medicine and Co-Director of Connors Center for Women's Health and Gender Biology, Brigham and Women's Hospital, Boston, MA. She is a Member of NAMS Board of Trustees and NAMS Professional Education Committee.

DISCLOSURE: Dr. Manson reports no conflicts.

(Disclaimer: Note that the opinions expressed in the newsletter and summarized in Contemporary OB/GYN are those of the authors and are not necessarily endorsed by NAMS.)