SATURDAY, Feb. 7, 2004 (HealthDayNews) -- You are more likely to suffer a stroke in the early morning than any other time, and this increased risk is linked to the body's natural rhythms.
Circadian rhythms seem to play a part in blood pressure, body temperature, and other body functions, new research finds. During the early morning, when blood pressure is higher, the risk for stroke appears to increase.
A stroke is a sudden loss of brain function, resulting from a loss of blood supply to part of the brain. When the stroke is caused by a blood clot it is called an ischemic stroke. Ischemic strokes account for 85 percent of the 600,000 strokes a year in the United States.
A stroke caused by a ruptured blood vessel in the brain, which results in bleeding, is called a hemorrhagic stroke.
In their study, the research team collected data on 735 men and women who had had a first stroke and were part of the Northern Manhattan Stroke Study from July 1993 and August 1997. Of these patients, 45 percent had their stroke between 6 a.m. and noon.
For the 431 patients whose time of ischemic stroke was known, 5 percent occurred between midnight and 6 a.m., 42 percent between 6 a.m. and noon, 30 percent between noon and 6 p.m. and 23 percent between 6 p.m. and midnight.
In addition, patients older than 70 had more strokes between 6 a.m. and noon compared to younger patients, the researchers report.
They also found that all types of ischemic stroke happened more commonly in the morning.
The researchers presented their findings Feb. 6 at the American Stroke Association's annual meeting in San Diego.
"We are not the first people to report this," says lead researcher Dr. Mitchell S. Elkind, an assistant professor of neurology at Columbia University College of Physicians and Surgeons and an assistant attending neurologist on the stroke service at New York Presbyterian Hospital.
It has been known for some time that there are circadian rhythms that dictate certain body functions, he adds. Elkind notes that blood pressure is higher in the morning and there are other physiological functions that change in the morning that might lead to an increased risk for stroke.
The prevalence for strokes in the morning was the same in every group they looked at: men and women, blacks, whites and Hispanics, Elkind says.
Elkind adds they had expected to see the same pattern for hemorrhagic stroke, but they didn't. He believes there were too few hemorrhagic strokes in the study group to determine a consistent pattern.
"It is important to remember that strokes can occur at any time of day," Elkind says. In addition to stroke, these circadian rhythms seem to apply to heart attack and breathing problems, which are also more common in the early morning, he adds.
The most important thing, Elkind says, is that "when you suspect that you or a family member is having a stroke, get to the hospital fast, because there are treatments available."
Dr. David L. Katz, director of the Yale Prevention Research Center at Yale University, comments that while the explanations for the increased risk of stroke and heart attack in the morning have to do with variations in hormone levels and blood pressure, "there is also a common-sense component: going from asleep in bed to the challenges of the day is stressful."
He adds that "this stressful transition is downright dangerous for those with underlying vascular disease."
Katz also notes this study emphasizes the need to manage vascular risk factors all day. "Medications that wear off before the early morning are not nearly as good as those that truly last 24 hours," he says.
The best defense against stroke or heart attack in the early morning or at any other time is healthy blood vessels, Katz says.
"Early morning stress does not cause strokes in people free of underlying vascular disease. This is an instance where the proverbial ounce of prevention is fully worth a pound of cure," he says.
"A health-promoting lifestyle -- prudent diet, no tobacco, regular physical activity -- over a lifetime may not eliminate early morning stress, but it will surely increase your chances of living through it unscathed," he says.