"Habitual Caffeine Intake and the Risk of Hypertension in Women," published in the Journal of the American Medical Association (JAMA) and authored by Wolfgang C. Winkelmayer, MD, ScD, et al., examined the association between caffeine intake and the incidence of hypertension in women.

"Caffeine acutely increases blood pressure, but the association between habitual consumption of caffeinated beverages and incident hypertension is uncertain," the authors noted.

The study was based on results from the Nurses' Health Studies (NHSs) I and II of 155,594 U.S. women free from physician-diagnosed hypertension followed up over 12 years (1990-1991 to 2002-2003 questionnaires). Caffeine intake and possible confounders were ascertained from regularly administered questionnaires. The associations with types of caffeinated beverages also were tested.

"During follow-up," the study found, "19,541 incident cases of physician-diagnosed hypertension were reported in NHS I and 13,536 in NHS II. In both cohorts, no linear association between caffeine consumption and risk of incident hypertension was observed after multivariate adjustment (NHS I, P for trend = .29; NHS II, P for trend = .53). Using categorical analysis, an inverse U-shaped association between caffeine consumption and incident hypertension was found. Compared with participants in the lowest quintile of caffeine consumption, those in the third quintile had a 13% and 12% increased risk of hypertension, respectively (95% confidence interval in NHS I, 8%-18%; in NHS II, 6%-18%). When studying individual classes of caffeinated beverages, habitual coffee consumption was not associated with increased risk of hypertension. By contrast, consumption of cola beverages was associated with an increased risk of hypertension, independent of whether it was sugared or diet cola (P for trend <.001)."

The authors, therefore, state, "No linear association between caffeine consumption and incident hypertension was found. Even though habitual coffee consumption was not associated with an increased risk of hypertension, consumption of sugared or diet cola was associated with it. Further research to elucidate the role of cola beverages in hypertension is warranted."

The American Beverage Association (ABA) issued the following statement in response to the article:

"The authors themselves acknowledge the limitations of their study and state that it is too soon to draw any conclusions regarding soft drinks.

"Other factors are known to be associated with hypertension, such as lifestyle, stress, personality, behavior and other health conditions, and further study could help determine the relative importance of these factors as compared to consumption of soft drinks.

"Importantly, no association was found in this study between hypertension and consumption of caffeine, one of the most widely studied ingredients in the food supply today. The study, involving more than 150,000 women, excludes caffeine as a risk factor for hypertension, not only in coffee and tea but most likely in soft drinks, which contain substantially less caffeine than these other beverages."

Sources: JAMA, ABA