Association of ambulatory blood pressure and dietary caffeine in adolescents

Background: Although relatively little is known about the responsible factors, there is an increased prevalence of essential hypertension in youth. Our previous research using casual blood pressure (BP) suggests a role for caffeine intake. The objective of this study was to assess the association between caffeine intake and ambulatory BP patterns among adolescents and to replicate our previous findings that compared caffeine intake to BP values obtained at a single time point. Methods: Eighty-two African-American and non-Hispanic white adolescents (15 to 19 years old) with normal systolic BP selected foods and beverages for a 4-day sodium-controlled diet. Subjects were stratified into three groups based on the amount of caffeine in these foods. Ambulatory BP measures (24-h) were recorded during I day of the 4-day diet. The effects of ethnicity, caffeine, and the interaction of ethnicity and caffeine on BP were assessed for daytime and nighttime hours controlling for gender and body mass index. Results: The level of dietary caffeine was positively associated with daytime systolic BP (F-2,F-76 = 3.1, P = .05, partial R-2 = 0.07) and daytime diastolic BP (F = 3.53(2,76), P =.03, partial R-2 = 0.07). Caffeine's effect on systolic BP was most pronounced for African-American subjects. These results replicated our earlier findings. There was no association between caffeine intake and nighttime BP. Conclusions: This investigation replicates and extends our previous findings that caffeine consumption impacts the BP of adolescents, during the daytime when sympathetic nervous system responses dominate BP control. Controlled studies that examine the pressor effects of caffeine intake at levels typical of the dietary patterns of today's adolescents are needed. (C) 2005 American Journal of Hypertension, Ltd.