The Heart of the Pressor Effect: Acute Caffeine Ingestion and Resting Heart Rate Variability

Rationale: Epidemiological research is yet to ascertain if caffeine consumption contributes to the development of cardiovascular disease. Consequently, there is a need for further experimental research to investigate the etiology of caffeine's effects on the cardiovascular system. Objectives: To examine the relationship between autonomic regulatory capacity and the cardiovascular response to caffeine ingestion. Methods: A block-randomized, double-blind, placebo-controlled, crossover experiment investigated the cardiovascular responses of 20 participants ( n = 10 males) to acute caffeine ingestion. In a novel approach within caffeine research, the underlying autonomic regulatory capacity of the participants was indexed by measuring resting heart rate variability (HRV) and used to guide the analyses of the cardiovascular responses. Results: Results indicated that at rest, caffeine exerted a significant increase on the blood pressure of participants with higher, but not lower, resting HRV. Placebo elicited no cardiovascular differences. This suggests that individuals with greater autonomic regulatory capacity are more responsive to the pharmacological effects of caffeine. Conclusion: Overall, the findings suggest that autonomic regulatory capacity may represent an interindividual difference that predicts differential cardiovascular responsivity to caffeine ingestion. Further research is required to replicate this novel finding.