Coffee intake and stroke risk

A new study has revealed that drinking more coffee than usual could double your risk of a stroke. Prior research suggests a high risk of heart attack and sudden cardiac death in the hour after coffee intake. However, the risk of stroke associated with exposure to coffee remains unclear. The researchers at Harvard Medical School hypothesised that caffeine intake is associated with an elevated risk of stroke. They examined 390 stroke victims from America (209 men and 181 women), comparing each one's coffee intake in the hour before their stroke with their usual consumption over the previous year. Around one in ten had drunk coffee less than an hour before falling ill.

Coffee consumption was linked with a risk of stroke in the subsequent hour twice as high as during the periods where there was no coffee consumption. No such association was found with caffeinated tea or cola. The risk was mainly confined to those who exceed their normal intake of a cup or so a day.

It was observed that light coffee drinkers who normally have no more than one a day are twice as likely to suffer a blood clot on the brain if they increase that by an extra cup or two. The risk of a potentially fatal stroke was highest in the hour following consumption. After two hours, the coffee's effects had worn off and the risk of a stroke passed. But the danger lies in occasional exposure to relatively higher caffeine levels, making light coffee drinkers more susceptible.

This could be because coffee-lovers who get through several cups a day become desensitised to the effects of caffeine, such as raised blood pressure, stiffening of the arteries and higher norepinephrine levels, a stress hormone that increases heart rate. Caffeine intake can contribute to increased blood pressure, the single biggest risk factor for stroke, but it is known that antioxidants found in certain foods and drinks, including coffee, can help in the prevention of stroke.