Does caffeine intake enhance absolute levels of cognitive performance?
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- Jarvis, M.J. Psychopharmacology (1993) 110: 45. doi:10.1007/BF02246949
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The relationship between habitual coffee and tea consumption and cognitive performance was examined using data from a cross-sectional survey of a representative sample of 9003 British adults (the Health and Lifestyle Survey). Subjects completed tests of simple reaction time, choice reaction time, incidental verbal memory, and visuo-spatial reasoning, in addition to providing self-reports of usual coffee and tea intake. After controlling extensively for potential confounding variables, a dose-response trend to improved performance with higher levels of coffee consumption was observed for all four tests (P<0.001 in each case). Similar but weaker associations were found for tea consumption, which were significant for simple reaction time (P=0.02) and visuo-spatial reasoning (P=0.013). Estimated overall caffeine consumption showed a dose-response relationship to improved cognitive performance (P<0.001 for each cognitive test, after controlling for confounders). Older people appeared to be more susceptible to the performance-improving effects of caffeine than were younger. The results suggest that tolerance to the performance-enhancing effects of caffeine, if it occurs at all, is incomplete.