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Regular Low-Dose Aspirin Reduces Risk of Stroke in Women by at Least 17%, Study Finds

Women ages 45 and older who take 100 milligrams of aspirin every other day reduce their risk of stroke by at least 17%, although aspirin does not appear to protect women against heart attacks as it does men, according to a study presented on Monday at the American College of Cardiology meeting in Orlando, Fla., the Washington Post reports (Stein, Washington Post, 3/8). The study, published online in the New England Journal of Medicine, was led by epidemiologist Julie Buring and conducted as part of the Women's Health Study (Kohn, Baltimore Sun, 3/8).

In the study, about half of the 39,876 participants took a 100-mg dose of aspirin every other day; the other half took a placebo. The study lasted 10 years (Washington Post, 3/8). During that time, researchers recorded 391 heart attacks and 487 strokes (Gorner, Chicago Tribune, 3/8). According to researchers, women taking aspirin had a 17% reduced risk for stroke, including a 24% reduced risk for the most common form of stroke caused by blood clots (Sternberg, USA Today, 3/8).

The benefit was partially offset by an increased risk of rare bleeding events, such as ulcers and brain hemorrhages (Winslow, Wall Street Journal, 3/8). Of women taking aspirin in the study, 127 experienced stomach or intestinal bleeding requiring a blood transfusion, compared with 91 women in the placebo group (Marchione, AP/Greensboro News & Record, 3/7). The overall risk of heart attack in women taking aspirin was reduced by 9%, but researchers said the amount was not statistically significant.

Benefit More Pronounced in Women Over 65

A separate analysis of data including 4,097 women ages 65 and older when they entered the study found that aspirin reduced their risk of stroke by 26% and their risk of heart attack by 34% (Chicago Tribune, 3/8). However, that group of women, which accounted for 10% of study participants, experienced nearly one-third of total adverse effects from aspirin (Winslow, Wall Street Journal, 3/8).

According to the Los Angeles Times, the study results suggest that, for women over age 65, "the decision to prescribe aspirin should be made on exactly the same basis as it is in men," although for younger women, "the risk in taking aspirin routinely may outweigh the benefit" because of the risk of gastrointestinal bleeding (Maugh, Los Angeles Times, 3/8).

Vitamin E Effects Also Studied

The study also examined whether women taking 600 international units of vitamin E experienced heart benefits. Women taking vitamin E every other day experienced no significant reductions in heart attack or stroke, although there was an unexpected 24% reduction in all heart-related deaths, including sudden cardiac death.

Buring said, "There is little evidence that vitamin E confers a benefit in well-nourished groups in terms of cardiovascular disease," although she recommended further study on the total cardiovascular death reduction (Fauber, Milwaukee Journal Sentinel, 3/8).


According to Buring, the aspirin study "demonstrates the importance of studying medical therapies among women as well as men" (AP/Greensboro News & Record, 3/7). In previous studies involving few or no women, researchers found a low-dose of aspirin can reduce the risk of heart attack among healthy participants who are about 45 years old by 32% to 44% (Los Angeles Times, 3/8). However, previous findings based on studies involving mostly men indicated that aspirin provided no stroke risk reduction, and, in fact, could slightly increase the risk of stroke (Winslow, Wall Street Journal, 3/8).

According to the American Heart Association, women have about 10% more strokes than heart attacks; men have about 40% fewer strokes than heart attacks (Los Angeles Times, 3/8). Researchers say it is unclear why men and women have difference reactions to aspirin (Baltimore Sun, 3/8). Buring noted that women's risk for heart attack increases as they reach menopause and experience a decline in estrogen production (Duenwald, New York Times, 3/8).

"Age 50 in men is biologically about age 60 in women in terms of their risk of cardiovascular disease," Buring said (Washington Post, 3/8). Researchers also said the disparity could stem from biological or genetic differences between men and women (Baltimore Sun, 3/8). According to the Journal, the study "should further spur interest" about "the issue of sex-based differences in drug interactions and disease" (Won Tesoriero, Wall Street Journal, 3/8).


Elizabeth Nabel -- director of the NIH's National Heart, Lung and Blood Institute -- said the study has "major public health implications" (AP/Greensboro News & Record, 3/7). She added, "The bottom line is that many women, especially those 65 and older, may benefit from taking low-dose aspirin every other day to prevent stroke. But it is important for women to weigh the risk and benefits of taking aspirin and to consult with their doctor" (Chicago Tribune, 3/8).

Buring said, "The fact that there was a benefit on stroke is very important for women because we had many more strokes in our study than we had heart attacks." She added, "It appears that for women over 65 there may be a net benefit from taking low-dose aspirin, but for women under 65 there might not be."

Sidney Smith, director of the center for cardiovascular medicine at the University of North Carolina and co-author of AHA guidelines for preventing heart disease in women, said, "The really big message here is that women need to know their risk" (New York Times, 3/8).

C. Noel Bairey Merz, a heart disease specialist at Cedars-Sinai Medical Center, said, "These results have shown for the first time that aspirin can prevent stroke, and it should really stimulate both women and men to go to their health care providers and have their risks assessed. There are tens of thousands of lives that we could be saving annually in the U.S. alone if we could get the right people to start taking this low-dose aspirin" (Shelton, Orlando Sentinel, 3/8). The study is available online.

Broadcast Coverage

NPR's "All Things Considered" on Monday reported on the study. The segment includes comments from Buring and Dr. Charles Hennekens, a study author from Florida Atlantic University (Knox, "All Things Considered," NPR, 3/7). The complete segment is available online in RealPlayer. In addition, NBC's "Nightly News" on Monday reported on the study. The segment includes comments from Buring (Bazell, "Nightly News," NBC, 3/7). The complete segment is available online in Windows Media.

Additional Studies

The results of several other studies presented on Monday at the meeting appear below.

  • Laughter: Nineteen of 20 individuals had more relaxed blood vessels and increased blood flow after they watched a scene from the 1996 comedy film "Kingpin" than after they watched a scene from the 1998 war film "Saving Private Ryan," according to a study conducted by University of Maryland researchers, USA Today reports. For the study -- led by Michael Miller, director of preventive cardiology at the UM Medical Center -- researchers took 160 blood vessel measurements before and after participants viewed scenes from the films (Sternberg [2], USA Today, 3/8). The study found that 14 participants experienced reduced blood flow after they watched the scene from the war film. According to the study, average blood flow increased by 22% when participants laughed and decreased by 35% in periods of mental stress (Reuters/Los Angeles Times, 3/8). Researchers said that the comedy film might have prompted the release of nitric oxide, which relaxes blood vessels (Sternberg [2], USA Today, 3/8). ABCNews' "World News Tonight" on Monday reported on the study. The segment includes comments from Miller and Dr. Robert Vogel from UM Medical Center (McKenzie, "World News Tonight," ABCNews, 3/7).

  • Pacemakers: Pacemakers can reduce heart failure mortality rates by 36%, according to a two-year study of 813 patients conducted by European researchers, USA Today reports. The study, led by John Cleland of Castle Hill Hospital in Britain, found that participants who had pacemakers and took beta blockers were 50% less likely to die than those who did not receive such treatment (Sternberg [3], USA Today, 3/8).
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