1. ¹Department of Medicine, State University of New York, USA
2. ²Millard Fillmore Hospitals, Buffalo, New York, USA
3. ³Departments of Psychiatry and Behavioral Sciences, Oklahoma City, Oklahoma, USA
4. ⁴Department of Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, USA
5. ⁵Veterans Administration Medical Center, Oklahoma City, Oklahoma, USA

Correspondence: Dr. Bong Hee Sung, Millard Fillmore Hospitals, Department of Cardiology, 3 Gates Circle, Buffalo, NY 14209.

^*This work was supported by the Oklahoma Center for the Advancement of Science and Technology, and by Grant HL-32050 from the National Heart, Lung, and Blood Institute.

Abstract

The present study examined the effects of caffeine on blood pressure (BP) regulation in hypertensive men during exercise. Twenty unmedicated, mild hypertensives (HT, BP= 140/90 to 160/105 mm Hg) and 12 age-matched, nonnotensives (NT, BP < 130/ 80 mm Hg) performed 30 min of extended bicycle exercise following a single dose of caffeine (3.3 mg/kg, equivalent to 2 to 3 cups of coffee) and placebo in a double-blind, cross-over design. Hemodynamic measurements were made at predrug, 40min postdrug and during exercise. At predrug baseline, HT had significantly higher HR (67 v 57 beats/min) and BP (141/96 v 118/72 mm Hg) than NT. At postdrug baseline, caffeine increased systolic and diastolic BP, and peripheral vascular resistance (P < .01 in all cases), decreased HR (P < .05) and did not significantly change stroke volume and cardiac output for both groups. During exercise, HR response was greater on caffeine day than placebo day in HT (P < 0.05) only. Systolic BP was consistently elevated on caffeine day compared to placebo day in both groups (P < .001). Diastolic BP was elevated in HT for 30 min of exercise on caffeine day, but this pressor effect disappeared at 15 min of exercise in NT. As a result, rate-pressure products were significantly higher on caffeine days in HT at postdrug and during exercise. On caffeine day, 7 (39%) HT and 1 (8%) NT showed an excessive BP response (>230 for systolic or >120 for diastolic) during exercise. In conclusion, caffeine has significant hemodynamic effects on mild hypertensives at rest and during exercise. The increased rate-pressure products following caffeine during exercise place a greater workload on the heart, and abstinence from caffeine, especially before exercise, may be beneficial for persons with hypertension.