The acute effects of decaffeinated coffee on cognitive function and brain activity: a single-center experience

Background Coffee is one of the most widely consumed beverages worldwide and is known for its beneficial effects on various diseases, which is often attributed to caffeine. However, other bioactive compounds in coffee also play an important role. The aim of this study was to investigate the acute effects of decaffeinated coffee. Methods Thirty-one healthy adults participated in the study. Resting-state functional magnetic resonance imaging (rs-fMRI), cognitive-behavioral tests, self-report scales, and physiological measures were completed at baseline and 30 min post-drink. Based on rs-fMRI, we used static and dynamic amplitude of low-frequency fluctuations (ALFF), fractional amplitude of low-frequency fluctuations (fALFF), and regional homogeneity (ReHo) to observe changes in spontaneous brain activity following acute decaffeinated coffee intake. Definitions of static- (s-) and dynamic- (d-) prefixes for resting-state metrics: Static indices (sALFF, sfALFF, sReHo) were calculated across the entire resting-state time course without sliding-window segmentation, representing the mean level of spontaneous brain activity during the whole scan session. Dynamic indices (dALFF, dfALFF, dReHo) were derived via a sliding-window approach: ALFF, fALFF or ReHo was computed within each successive window, and the standard deviation of these window-wise values was taken as the final dynamic metric, reflecting the temporal variability of regional spontaneous neural activity. Results After consumption, participants showed significantly faster reaction times in the 1-back ( p = 0.002), 2-back ( p = 0.023), Continuous Performance Test ( p = 0.003), and Finger Tapping Task ( p = 0.009). At the neural level, the participants showed significantly higher sfALFF in the fusiform gyrus (FFG) and inferior temporal gyrus (ITG) and significantly lower sReHo in the medial orbital of the superior frontal gyrus (PFCventmed) after consuming decaffeinated coffee compared with before, with no significant differences in sALFF. The sfALFF values in the FFG were significantly negatively correlated with RTs on Continuous Performance Test (CPT). Dynamic analysis revealed significantly lower dALFF values in the FFG and cerebellum, and significantly higher dALFF and dReHo values in the supplementary motor area (SMA). No brain regions showed significant differences in dfALFF after consuming decaffeinated coffee compared with before (GRF-corrected, voxel-level p < 0.01, cluster-level p < 0.05). In addition, diastolic blood pressure significantly increased ( p = 0.004), and headache scores were higher ( p = 0.033), while no significant changes in systolic blood pressure or heart rate were observed. Conclusion These results suggest that decaffeinated coffee may affects cognitive performance and brain activity, providing insights into the effects of non-caffeine components of coffee and their underlying mechanisms. As an initial exploratory study, it provides a foundation for future research. Randomized, placebo-controlled trials with long-term assessments are now needed to validate and extend these findings.