Revisiting the evidence on caffeine mouth rinse: effects on exercise and cognitive performance: a meta-analytic review

Abstract

Background: Caffeine mouth rinsing (Caff-MR) may activate oropharyngeal receptors and rapidly engage central networks for motivation, attention, and pacing without systemic absorption. The only prior meta-analysis found no stable ergogenic effect, yet the evidence base has continued to expand and remains heterogeneous. Methods: Six electronic databases were searched up to 2 October 2025 for Caff-MR studies on exercise and cognitive outcomes. Study quality was assessed using modified PEDro and RoB-2. Three-level meta-analyses synthesized both outcomes. Prespecified moderators were sex, training status, habitual caffeine use, feeding state, exercise or cognitive type, rinse duration, and total oral exposure. Sensitivity analyses addressed assumed within-subject correlations, outliers, and influential cases. Results: Thirty-one studies (k = 167 effects) met inclusion. Caff-MR was associated with trivial-to-small improvements in exercise performance (k = 114; g = 0.12, p = 0.01). Benefits were most consistent for aerobic endurance and in the fed state; ~5-s rinses outperformed longer durations. Primary dose–response suggested a U-shape (32–133 mg window), but this pattern was not robust to outlier removal; under 5-s conditions, higher total exposure related negatively to performance. Cognitive effects were inconsistent overall (k = 53; g = 0.23, p = 0.07), yet after outlier removal the overall and speed-based effects reached significance, whereas accuracy remained variable. Risk of bias was predominantly “some concerns”; GRADE certainty was moderate (exercise) and very low/low (cognition). Conclusions: Caff-MR is a practical, ingestion-free strategy yielding small, context-dependent benefits, optimized by brief (~5 s) rinses and moderate exposure, particularly for aerobic endurance. Standardized, well-powered trials are needed to refine dosing, timing, and cognitive applications.