Cortical arousal and autonomic regulation: The role of cold <i>vs</i> tepid caffeinated beverages during prolonged orthostasis

BACKGROUND: The interplay between caffeine ingestion, beverage temperature, and orthostatic stress on cortical arousal and autonomic regulation remains poorly understood. Understanding these distinctions is critical in identifying non-pharmacologic strategies for mitigating orthostatic intolerance, presyncope, and fatigue. Furthermore, electroencephalogram (EEG) biomarkers may provide objective insights into cortical-autonomic coupling during prolonged standing. This emerging perspective offers a novel translational pathway for optimizing performance and well-being in both clinical and occupational settings. AIM: To investigate the effect of ingesting cold and tepid caffeinated beverages on brain waves during prolonged orthostasis. METHODS: Thirty-six male individuals, averaging 20 years old, who satisfied the inclusion criteria were selected using respondent-driven sampling. Caffeinated beverages containing 10-12 mg of caffeine per 100 mL at 10 °C (cold) or 37 °C (tepid) were used for the study. Baseline EEG and pulse rate in a sitting position were recorded. Orthostasis was defined as standing upright from a sitting position and lasting 20 min. An EEG was conducted using PowerLab 26T. RESULTS: Pulse rate was significantly elevated by orthostasis when compared with the baseline. Cold caffeinated beverages decreased the alpha/beta ratio and increased beta wave frequency when compared with tepid caffeinated drinks. Orthostasis also increased beta wave frequency but decreased alpha wave frequency and the alpha/beta ratio when compared with baseline. However, orthostatic individuals administered tepid caffeinated beverage showed no significant difference in the alpha/beta ratio with orthostatic individuals administered a cold caffeinated beverage. CONCLUSION: Neither cold nor tepid caffeinated beverages altered EEG responses to prolonged orthostasis; caution is advised during standing, particularly for elderly individuals and patients prone to orthostatic syncope or autonomic disorders.