DURATION OF CAFFEINE ABSTENTION INFLUENCES THE ACUTE BLOOD-PRESSURE RESPONSES TO CAFFEINE IN ELDERLY NORMOTENSIVES

The effect of an acute oral caffeine load (250 mg capsule) and matching placebo on blood pressure and pulse rate were studied after 48 h caffeine abstention in 8 elderly, normotensive regular caffeine users. The caffeine loading phase was repeated after only 12 h abstention. Following 48 h abstention, supine systolic and diastolic blood pressure were higher for the 120 min study period after the acute caffeine load than placebo (12.1 mm Hg, 95 % C.I. 4.3-19.9 mm Hg; P = 0.008 and 7.4 mm Hg, 3.6-11.2 mm Hg; P < 0.001 respectively). Similar differences were seen in standing blood pressure, though pulse rate was unchanged throughout. The pressor response to the acute caffeine load was significantly greater after a 48 h than a 12 hour caffeine abstention period, for supine and standing systolic and diastolic blood pressure. The changes in plasma caffeine levels after acute loading were similar after the 2 different abstention periods. Caffeine ingestion after 48 h abstention has an acute pressor effect in normotensive elderly subjects which is abolished if the abstention period is reduced to 12 h. Acute caffeine ingestion is unlikely to have a significant pressor effect in elderly normotensive subjects who are regular caffeine users as the normal period of caffeine abstention (i. e. overnight) is too short to abolish tolerance.