Caffeine and Blood Pressure Regulation in Hypertension

Principal Investigator: William Lovallo, PhD

Abstract:

The goal of this project is to examine whether caffeine has a persistent effect on blood pressure and stress hormone levels in men and women with hypertension.  Caffeine taken acutely raises blood pressure (BP) for several hours, and this effect is larger in persons developing hypertension and in unmedicated hypertensives.  Caffeine's health consequences are often considered negligible based a presumption that regular use causes pharmacologic tolerance.  However, we do not know if regular intake eliminates caffeine's BP and stress hormone responses in hypertensives.  This study will be an extention of our previous work showing lack of complete tolerance in normotensive adults and our work using acute caffeine doses in hypertension risk groups.  Hypertensive patients will be tested in a 2-week, double-blind, crossover study of caffeine vs. placebo effects on blood pressure (BP) and levels of the stress hormone, cortisol.  Subjects will meet diagnostic criteria for Stage I hypertension (BP=140-159 mmHg systolic or 90-99 mmHg diastolic) or be medicated for essential hypertension.  On a caffeine week they will consume unmarked capsules at home for 5 days (200 mg/capsule x 2=400 mg/day), undergo ambulatory BP monitoring on day 5 and visit the laboratory for a test protocol on day 6, where they will have a single challenge dose of 200 mg on the morning of testing and be monitored at rest and during behavioral stress.  On the placebo week, all capsules will contain 0 mg of caffeine.  This allows us to evaluate the BP and cortisol in at rest and during controlled stressors in relation to a daily caffeine dose similar to that taken in the diet of the average adult coffee consumer.  The design accordingly allows a comparison of a caffeine effects using a highly sensitive within-person design.  We predict that hypertensive patients will have the large and persistent BP and cortisol responses to both dietary and challenge doses of caffeine.  These responses are expected to persist despite 5 days of intake of a moderately high dose of caffeine (400 mg/day).  A persistent effect of caffeine on BP in these patients would have an adverse impact on achieving BP reduction through lifestyle modification or medication.

Patient Inclusion Criteria:

Patient Compensation:

Contact Information:

William Lovallo, PhD (405) 270-0501  Ext 3124