DURHAM, N.C. -- Drinking a few extra mugs of coffee each day can boost blood pressure, heart rate and stress levels enough to increase a person's risk of developing heart disease over a lifetime of moderate caffeine consumption, according to a Duke University researcher.
In a study of 19 habitual coffee drinkers who wore "ambulatory" blood-pressure monitors throughout their daily jobs, the researcher found that the equivalent of four to five cups raised blood pressure an average of five points, compared to days when they consumed only one cup. The effect occurred within an hour of consumption, and the subjects' blood pressure remained elevated throughout the day, the study found.
The volunteers also reported higher levels of stress during the day when they received the higher, 500-milligram dose of caffeine, and they showed a corresponding increase in heart rate, said James Lane, associate research professor of psychiatry at Duke and lead author of the study. Results of the study, funded by the National Heart, Lung and Blood Institute, are published in the May issue of the journal Psychosomatic Medicine.
While a 5-point increase in blood pressure is not excessive, it can have significant clinical implications over time, Lane said. A review of nine major studies of blood-pressure and cardiovascular-disease risk showed that a 5-point difference in diastolic blood pressure -- the lower number used to assess health risk -- was associated with at least a 34 percent increase in the incidence of stroke and a 21 percent increase in the incidence of coronary heart disease.
In another unrelated study, called the Hypertension Detection and Follow-up Program, researchers reported that reducing blood pressure by five points through medication was associated with a 20 percent reduction in 5-year mortality, Lane said.