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Daybreak Is Dangerous for Heart Attacks

But men more likely than women to die during night attacks, says study

TUESDAY, Nov. 13, 2001 (HealthDayNews) -- Men and women may not be created equal when it comes to the timing of fatal heart attacks, new research suggests.

A Brazilian study has found that in the deaths of 508 heart attack patients, men tended to expire just before midnight and during the dawn, while women were most vulnerable just before sunrise.

"This study is an observational study with an unexpected finding," says Dr. Jose Fabri Jr., lead author. "We will now study what different factors could be responsible for these differences."

Fabri says his group came across the finding by accident, but he suggests that circadian rhythms and differences in heart parameters between men and women might explain the phenomenon. His group next plans a clinical trial in which heart patients will be given beta-blocker drugs, which combat the hardening of the arteries that usually accompanies heart disease.

"Generally, this disease is more severe in men than women," Fabri says. Add to that the fact that circadian rhythms, the biological ebb and flow of our body's hormone levels and bodily functions, mean increased blood flow to the heart at night.

"It makes it harder for men to tolerate heart attacks at night," he explains.

Fabri's group first decided to examine when people were most likely to die from heart attacks because previous studies have suggested the early morning hours are the most lethal.

In the study, the deaths of 508 patients who were hospitalized were analyzed. Of the 508, 308 were men and 200 were women. The average age of the patients was 59. They were all admitted with symptoms of heart failure, and received the standard treatment for their condition, which included bed rest, diet, ACE inhibitors, diuretics and digoxin for chest pain. The researchers found the men were most likely to die between 5 a.m. and 6:57 a.m., and also between 11 p.m. and midnight. The women were most likely to die just before dawn.

"I think it's very interesting; why there's this second peak in men," says Dr. Rose Marie Robertson, director of the Women's Heart Institute at Vanderbilt University. "It's not shown up in outpatient studies so far. This finding is a novel finding that deserves further research."

Fabri suggests that hormones may also be at play here, but he cautions that it's too soon to tell for sure.

Another cardiac expert agrees the findings are confounding.

"God knows what this means," says Dr. Irving Kron, chairman of cardiothoracic surgery at the University of Virginia Medical Center. "It's just so hard to know. I've never seen this, and it's not been talked about before. There aren't that many people that die in their sleep. It's not as common as you might think."

Kron notes that in a population study like Fabri's, it's hard to eliminate factors that may be skewing the results. The findings of a randomized clinical trial are much more definitive, he adds.

"There's no doubt in my mind there are some gender differences in these types of events, but I can't find the logic in this one. The data set is too small," Kron says.

That's exactly why Fabri says his group plans to start a clinical trial where 1,000 heart patients will be given beta-blocker drugs. That trial will observe the patients for two to three years.

Despite advances made in identifying the causes of heart disease and new treatments for it, experts say they still don't know why women experience heart attacks differently than men -- why they're more likely than men to have the less common symptoms, why younger women who have heart attacks are more likely to die than men and what role estrogen plays in heart disease.

"The differences between men and women are really still incompletely understood," says Robertson. "The field is ripe for further investigation and clarification."

That's why, after years of heart attack studies that looked only at men, the National Institutes of Health (NIH) now insists that all such studies include women.

The use of beta blockers to treat heart disease is also new territory for researchers.

In one of the first human studies of beta blockers and heart disease, Swedish scientists recently found that daily doses of beta blockers slowed thickening of the arteries by roughly 40 percent in people with early signs of coronary disease.

Experts say beta blockers may become as common as aspirin, a blood thinner that many people take daily to prevent heart attacks. Yet the prescription drugs can cause occasional impotence and depression.

Fabri says he hopes this latest study might eventually change the way doctors treat their male and female heart patients.

"We expect to change the view of physicians about the physiological course of this in the night, and have them change medications with men to act on these changes," he says.

What To Do

For more on exactly how heart failure happens, go to the American Heart Association.

To read more about beta blockers, visit the American Academy of Family Physicians or the Heart Information Network.

SOURCES: Interviews with Jose Fabri Jr., M.D., assistant physician, Brazil Heart Institute, University of Sao Paulo Medical School, Saõ Paulo, Brazil; Irving Kron, M.D., chairman, cardiothoracic surgery, University of Virginia Medical Center, Charlottesville, Va.; Rose Marie Robertson, M.D., director, Women's Heart Institute, Vanderbilt University, Nashville, Tenn.; Nov. 13, 2001, presentation, American Heart Association's Scientific Sessions 2001 conference, Anaheim, Calif.
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