Caffeine Induced Changes in Cerebral Circulation

Caffeine Induced Changes in Cerebral Circulation To the Editor: We reported significant reductions in cerebral blood flow (CBF) 30 minutes and 90 minutes after the oral administration of 250 mg of caffeine in 14 normal volunteers (age 26 yrs, S.D. 6) in the SeptemberOctober 1985 issue of Stroke. As an extension of this study, we evaluated CBF responses to similar doses of caffeine in elderly subjects. The design of the experiment was identical to the one reported in our previous paper on the subject. CBF was measured with the '"Xenon inhalation technique before and 30 minutes and 60 minutes after the oral administration of 250 mg of caffeine or a placebo in groups of elderly subjects (age caffeine group 64 yrs, S.D. 9, four males and six females; placebo group 62 yrs, S. D. 5, three males and six females). The subjects were assigned to the caffeine and placebo group in a random fashion and the drug/placebo was administered under double-blind conditions. The CBF values obtained during the three measurements from the elderly and younger subjects (young-placebo, young-caffeine, elderly-caffeine, elderly-placebo) were compared using repeated measure analysis of variance (group x drug x period x region x hemisphere) (table 1). Significant group x drug x period interactions were found. Post hoc Newman-Keuls showed significant reduction in CBF, both at 60 minutes and 90 minutes after the administration of caffeine in the young patients only. None of the other groups showed any significant change in CBF values. The results of the study suggest reduced CBF responsiveness to caffeine in elderly subjects. The exact reason for this finding is unclear. Loss of elasticity of the cerebral capillaries and impairment of neurotransmission associated with aging might be responsible. It is also possible that there might be age-related changes in the pharmacokinetics of caffeine. It should be noted that cerebral blood flow responsiveness to hypercarbia, hypocarbia, hyperoxygenation, sensory stimulation and slow wave sleep have also been reported to be blunted in the elderly as compared to the young. Roy J. Matbew, M.D. Professor of Psychiatry References 1. Mathew RJ, Wilson WH: Caffeine induced changes in cerebral circulation. Stroke 16: 814-817, 1985 2. Shaw T, Meyer JS: Aging and cerebrovascular disease. In: Meyer JS, Shaw T (eds). Diagnosis and Management of Strokes and TIAs. Menlo Park, California: Addison-Wesley Publishing Co, 1982