Chronic effects of habitual caffeine consumption on laboratory and ambulatory blood pressure levels.
BACKGROUND
Uncertainty continues to surround the role of habitual caffeine consumption as a cardiovascular risk factor. The present study examined the effects of moderate caffeine intake on 24h blood pressure and heart rate in normotensive men and women.


METHODS
A double-blind, placebo-controlled, crossover design with counterbalancing was used, in which 36 healthy men and women participated in four experimental conditions involving the ingestion of placebo or caffeine three times daily for 6 days, followed by a seventh ('challenge') day of placebo or caffeine ingestion.


RESULTS
When caffeine was consumed on the challenge day, blood pressure was found to be elevated immediately after caffeine ingestion and was either unchanged or decreased (hypotensive effect) after a period of abstinence from the drug. Some diminution of the peak pressor effects was found when participants ingested caffeine after habitual use of the drug (6.0/5.2 mmHg) compared with when they had been abstinent before the challenge day (7.7/6.8 mmHg). This diminution in the reaction was comparatively small, however, and pressor effects persisted on caffeine-challenge days even when caffeine was consumed on preceding days.


CONCLUSIONS
Habitual consumption diminished, but did not eliminate, the pressor effects of caffeine. Considering the almost universal consumption of caffeine beverages, the persistent pressor effects of the drug could have important implications for cardiovascular health.
James
J E
JE
School of Behavioural Health Sciences, La Trobe University, Melbourne, Victoria, Australia.
D000293:Adolescent; D000328:Adult; D000704:Analysis of Variance; D001794:Blood Pressure / Q000187:drug effects*; D018660:Blood Pressure Monitoring, Ambulatory; D002110:Caffeine / Q000008:administration & dosage / Q000009:adverse effects*; D018592:Cross-Over Studies; D004311:Double-Blind Method; D005247:Feeding Behavior; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D008297:Male; D008875:Middle Aged; D013268:Stimulation, Chemical; D013997:Time Factors
D002110:Caffeine