CAFFEINE RAISES BLOOD-PRESSURE AT WORK

Objective: The study investigated the effects of moderate doses of caf feine on ambulatory blood pressure and heart rate during workday activ ities. Methods: Healthy, nonsmoking, habitual coffee drinkers (N = 21) received daily doses of 100 mg and 500 mg of caffeine on 2 days in a crossover design. Treatment order was random and counterbalanced, and administration was double-blind. Ambulatory monitoring was conducted f or 6 to 9 hours during normal workday activities and diary entries wer e completed at each measurement. Ambulatory data were analyzed for the effects of caffeine dose, controlling for variations in posture, phys ical activity, and perceived stress. Results: The average workday bloo d pressure and heart rate were significantly higher when the higher do se of caffeine was consumed. Controlling for other factors, dose-relat ed differences were 4 mm Hg for systolic and 3 mm Hg for diastolic blo od pressure, and were 3 bpm for heart rate. Conclusions: Results suppo rt earlier evidence that caffeine raises blood pressure at work, and d emonstrate that these presser effects are independent of changes in po sture, physical activity, or stress. Daily blood pressure increases as sociated with caffeine consumption could increase the risk of developi ng cardiovascular diseases. In addition, caffeine consumption effects might confound ambulatory investigations of the cardiovascular effects of other psychosocial, personality, or health-behavior factors.