Clinical Question: Does habitual caffeine intake increase the risk of hypertension in women?
Study Design: Cohort (prospective)
Synopsis: Caffeine intake acutely raises blood pressure, but the association between habitual intake and the risk of developing hypertension has been unclear. Investigators examined data obtained from two large-scale prospective cohort studies—the Nurses’ Health Studies (NHS) I and II. The NHS I cohort was assembled in 1976 with 121,700 female registered nurses, 30 to 55 years of age, reporting via self-completed questionnaire every two years. NHS II began in 1989 with 116,671 female registered nurses, 25 to 42 years of age, also reporting via self-completed questionnaire every two years. Follow-up for both cohorts occurred for more than 90 percent of participants. Questionnaires requested food and beverage intake measurements and collected data on various health outcomes including hypertension. Participants were not aware of the study hypothesis regarding a potential link between caffeine intake and hypertension. Health record reviews confirmed documented hypertension in a subset of women. In both cohorts, no significant linear association was detected between increasing caffeine consumption and the risk of developing hypertension. In subgroup analysis with multivariate adjustments, habitual coffee and tea consumption did not increase the risk of hypertension, but a significant association between consumption of cola beverages (sugared and diet) and the diagnosis of hypertension did exist.
Bottom Line: Habitual caffeine consumption does not appear to increase the risk of hypertension in women. In particular, coffee and tea are not associated with increased risk. The development of hypertension is, however, significantly associated with the intake of cola drinks, including sugared and diet versions. (Level of Evidence: 2b)