Background: The aim of this study was to characterize the acute effects of caffeine on peripheral and central blood pressure (BP) in healthy individuals, using validated noninvasive techniques.
Methods: In a randomized double-blind study, 300 mg caffeine or matching placebo was administered orally to 20 healthy adults and hemodynamic responses were observed. Central BP and augmentation index (AIx) were determined by pulse wave analysis; cardiac index (CI) was estimated by transthoracic bioimpedance; and heart rate variability (HRV) given by power spectral analysis of pulse interval. Pressure amplification (peripheral to central pulse pressure ratio) and systemic vascular resistance index were also calculated.
Results: Caffeine administration increased central systolic and diastolic BP by 7 +/- 3 (P <.01) and 3 +/- 2 mm Hg (P <.05), respectively (mean +/- SEM) at 45 min, but had no effect on peripheral BP. Caffeine caused AIx to increase by 7 +/- 2 and 0 +/- 1%, respectively (P <.05), and pressure amplification to decrease by 1.0 +/- 0.1 v 0.2 +/- 0.2 (P <.001) placebo at 45 min.
Conclusions: Acute caffeine intake significantly increases central BP and large artery waveform transmission and diminishes pressure amplification in healthy adults. Therefore, the effects of caffeine on BP may be significantly underestimated by measurement of BP at the brachial artery.