Stroke Risk Reduction Found In Women Who Consume Coffee
< Feb. 18, 2009 > -- Spanish and American researchers suggest that drinking coffee appears to lower the risk for stroke among women, with more consumption translating into more protection.
The study finds that consuming two or more cups of coffee a day can even boost protection for nonsmokers.
The findings were released in an issue of the medical journal Circulation. The study tracked both coffee habits and stroke occurrence among tens of thousands of American women across nearly a quarter century. It addressed earlier indications that coffee might offer some protection against diabetes, while not raising the risk for heart trouble.
However, the current evidence also includes a cautionary note for smokers. Their habit seems to wipe out whatever protection long-term coffee drinking might otherwise provide.
"Many people have been very concerned that coffee might actually be a risk factor for stroke, that it might, in fact, increase the risk of stroke," says study's co-author, Dr. Rob M. van Dam, an assistant professor at Harvard Medical School and Harvard School of Public Health. "But here we saw that it might end up being beneficial rather than detrimental."
Coffee Consumption and Stroke Risk - Is There a Link?
To explore possible links between coffee drinking and stroke risk among women, the authors analyzed data on more than 83,000 women, whose age averaged about 55 and had participated in the Nurses' Health Study between 1980 and 2004. At the start of the study, none of the women had a history of stroke, heart disease, diabetes or cancer.
Based on the women's answers on seven food-habit surveys administered during the study, the researchers found that 84 percent of the women consumed at least some caffeinated coffee. Half said they drank decaffeinated coffee, 78 percent drank tea and 54 percent drank caffeinated sodas.
During the study's 24-year span, nearly 2,300 strokes occurred. More than half were ischemic strokes, which followed blood vessel blockage.
However, coffee drinking was not linked to either the lowered the increased risk of stroke among women who developed high blood pressure, diabetes, or high cholesterol.
But after considering factors such as cigarette and alcohol consumption, Dr, van Dam and his colleagues found that healthy women who consumed two to three cups of caffeinated coffee a day had, on average, a 19 percent lower risk for any kind of stroke than did women who drank less than one cup a month. Drinking four or more cups a day lowered risk by 20 percent.
Women who drank five to seven cups of coffee a week were 12 percent less likely to have a stroke than were those who downed just one cup a month, the study concludes.
Stroke Risk Reduced In Smokers
Noting that coffee drinkers are often also smokers, the research team focused on the impact tobacco might have on the coffee-stroke link.
What they found was striking - among women who never smoked or had smoked but quit, drinking four or more cups of coffee a day conferred a 43 percent reduced risk for all types of stroke. However, among women with similar coffee habits who also smoked, stroke risk fell by just 3 percent.
It remains unclear what specific ingredient in coffee plays the principal role of stroke risk reduction. However, the researchers note that caffeinated tea and soft drinks carried no similar benefit - implying that some other component in coffee, apart from caffeine, might provide the protective effect.
More Coffee Studies Ahead
Although the link between coffee consumption, smokers, and stroke risk reduction seems favorable, the study authors point out that certain conditions - such as insomnia, anxiety, high blood pressure, and cardiac complications - can be negatively affected by coffee drinking.
They further cautioned that the current findings need confirmation with continued research.
"This is quite an early finding," Dr. van Dam states "And previous studies have been quite small. But the data we do have is very convincing in the sense that we feel comfortable that we definitely found no association between high coffee consumption and a higher stroke risk. So women can continue to enjoy their coffee and focus on other things to reduce stroke risk, such as engaging in more physical activity, reducing salt intake, and stopping smoking."
Dr. Anthony Comerota, director of the Jobst Vascular Center at Toledo Hospital in Ohio, describes the degree of benefit as "somewhat surprising."
"But what is not surprising," he says "is the deleterious impact of cigarette smoking, which we know is the most potent risk factor - perhaps other than diabetes - for heart attack and stroke and general cardiovascular-related risk among both men and women."
Dr. Comerota suggests that future research should explore physical activity patterns among coffee drinkers and nondrinkers. "There may be behavior patterns which link increased physical activity with coffee drinking," he notes, "and we know the more physical activity one has, the better cardiovascular risk reduction that person enjoys.
A Related Study: Diet and Stroke Risk
Another large study appearing in the same issue of Circulation offered insight into the impact of diet on stroke risk. It noted that American women who closely follow a traditional Mediterranean diet (high in monounsaturated fats, plant-based proteins, whole grains and fish) have a much lower risk for both heart disease and stroke.
As with Dr. van Dam's research, this study - led by Dr. Teresa T. Fung of Simmons College and the Harvard School of Public Health - was also based on analysis of participants in the Nurses' Health Study, nearly 75,000 of whom were tracked for two decades to see how their dietary habits stacked up against their incidence of both stroke and heart attack.
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What Are The Different Types of Stroke?
Strokes can be classified into two main categories: ischemic strokes and hemorrhagic strokes.
An ischemic stroke occurs when a blood vessel that supplies the brain becomes blocked or "clogged" and impairs blood flow to part of the brain. The brain cells and tissues begin to die within minutes from lack of oxygen and nutrients. The area of tissue death is called an infarct. About 88 percent of strokes fall into this category. Ischemic strokes are further divided into two groups, including the following:
thrombotic strokes -strokes caused by a thrombus (blood clot) that develops in the arteries supplying blood to the brain. This type of stroke is usually seen in older persons, especially those with high-cholesterol levels and atherosclerosis (a build-up of fat and lipids inside the walls of blood vessels).
Sometimes, symptoms of a thrombotic stroke can occur suddenly and often during sleep or in the early morning. At other times, it may occur gradually over a period of hours or even days. This is called a stroke-in-evolution.
Thrombotic strokes may be preceded by one or more "mini-strokes," called transient ischemic attacks, or TIAs. TIAs may last for a few minutes or up to 24 hours, and are often a warning sign that a stroke may occur. Although usually mild and transient, the symptoms caused by a TIA are similar to those caused by a stroke.
A type of stroke that occurs in the small blood vessels in the brain is called a lacunar infarct. The word lacunar comes from the Latin word meaning "hole" or "cavity." Lacunar infarctions are often found in people who have diabetes or hypertension (high blood pressure).
Another type of ischemic stroke is called an embolic stroke. Embolic strokes are usually caused by an embolus (a blood clot that forms elsewhere in the body and travels through the bloodstream to the brain). Embolic strokes often result from heart disease or heart surgery and occur rapidly and without any warning signs. About 15 percent of embolic strokes occur in people with atrial fibrillation, a type of abnormal heart rhythm in which the upper chambers of the heart do not beat effectively.
Hemorrhagic strokes occur when a blood vessel that supplies the brain ruptures and bleeds. When an artery bleeds into the brain, brain cells and tissues do not receive oxygen and nutrients. In addition, pressure builds up in surrounding tissues and irritation and swelling occur. About 11 percent of strokes are caused by hemorrhage. Hemorrhagic strokes are divided into two main categories, including the following:
An aneurysm is a weakened, ballooned area on an artery wall and has a risk for rupturing. Aneurysms may be congenital (present at birth), or may develop later in life due to such factors as hypertension or atherosclerosis.
An AVM is a congenital disorder that consists of a disorderly tangled web of arteries and veins. The cause of AVM is unknown.
The recurrence of stroke occurs in about 25 percent of stroke victims within five years after a first stroke. The risk is greatest right after a stroke and decreases over time. The likelihood of severe disability and death increases with each recurrent stroke. About 3 percent of stroke patients have a second stroke within 30 days of their first stroke, and about one-third have a second stroke within two years.
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