Acute caffeine administration impaired spatial working memory in habitual coffee/tea drinkers: A randomized, placebo-controlled, double-blind study.
Level 2 - randomized trial
Randomized, double-blind, placebo-controlled trial.
PubMed 39244155 · doi:10.1016/j.clnesp.2024.08.028
What was done
Eighteen healthy habitual coffee/tea drinkers participated in a randomized, double-blind, placebo-controlled study evaluating the acute effects of 200 mg oral caffeine versus placebo. Working memory was evaluated using backward digit span (verbal working memory) and spatial span tasks (spatial working memory) across delay conditions (0, 4, 8, and 6 seconds). Total scores and maximum scores achieved were the primary outcome variables, analyzed as a secondary analysis of previously published trial data.
What was found
Caffeine significantly impaired spatial working memory compared to placebo in a delay-independent manner (maximum score p = 0.013; total score p = 0.007). There were no significant main effects of caffeine on verbal working memory (maximum score p = 0.82; total score p = 0.56). Mean values, standard deviations, and effect sizes were not reported in the abstract.
Why it matters
These findings challenge the common belief that caffeine universally enhances cognition, indicating that acute caffeine administration may selectively impair spatial working memory in habitual consumers.
Limits
The sample size was very small (n = 18), limiting statistical power and generalizability. The abstract does not report baseline values, absolute effect sizes, or confidence intervals. The findings represent a re-analysis of previously collected data and are limited to habitual consumers receiving a single 200 mg dose.
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