The Study
Maintenance of Vagal Tone with Time-Release Caffeine, But Vagal Withdrawal During Placebo in Caffeine-Habituated Men
This study gave different kinds of caffeine to 10 guys who drink a lot of coffee and measured how their heart rhythms changed. It shows that caffeine might help keep their heart's calming system working better than when they didn't get caffeine—but it's only one small test, so we can't be super sure.
Analysis score
Maximum 90 for a randomized controlled trial.
Where the score came from
People who drink a lot of coffee every day may need it to keep their heart’s calming system working properly.
Where does this study sit?
Reviews of RCTs (Meta-analyses)
Max 100Randomized Trials
Max 90Reviews of Cohort Studies
Max 85Cohort Studies
Max 72Reviews of Case-Control Studies
Max 63Case-Control Studies
Max 58Cross-Sectional & Case Series
Max 50Expert Opinion
Max 546 / 100
Quality score
Participants are randomly assigned to treatment or control groups, minimizing bias. The gold standard for testing whether an intervention causes an effect.
Key takeaways
Summary
Based on the study abstract and findings.
- 1Yes — this suggests caffeine helps maintain the body’s natural calming signal to the heart in regular users, and skipping it may reduce this protection.
- 2After 6 hours, people who took caffeine had a heart rate variability score of 0.84, while those who took placebo had 0.79 — a small but significant difference.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
Journal of Caffeine and Adenosine Research
Year
2018
Authors
Michael B. La Monica, D. Fukuda, Ran Wang, Adam M. Gonzalez, Adam J. Wells, J. Hoffman, Jeffrey R Stout
Related Content
Claims (7)
Drinking too much coffee or energy drinks over a long time can keep your body in 'fight or flight' mode, making your heart race and increasing your chances of irregular heartbeats and heart strain.
High levels of caffeine maintain continuous activity in the body's fight-or-flight system and reduce activity in the rest-and-digest system.
In young adults who regularly consume at least 200 mg of caffeine daily, a 194 mg dose of caffeine—whether time-release or instant—prevents the decline in parasympathetic nervous system activity measured by the HF/TP ratio of heart rate variability over 8 hours, while a placebo causes a measurable decline.
In people who regularly consume caffeine, stopping caffeine intake for 8 hours reduces a specific measure of heart rate variability that reflects parasympathetic nervous system activity.
In young people who regularly consume caffeine, the high-frequency component of heart rate variability relative to total power is higher six hours after caffeine intake compared to a placebo, but other heart rate variability measures show no difference.
In people who regularly consume caffeine, a slow-release 194 mg caffeine pill has the same effect on parasympathetic nervous system activity as a regular 194 mg caffeine pill over eight hours.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.