The Study
Concentration–effect relationships of plasma caffeine on EEG delta power and cardiac autonomic activity during human sleep
This study gave people caffeine or a sugar pill and measured how their brain and heart behaved during sleep. Because they randomly picked who got what and didn't tell anyone, we can say caffeine probably caused the changes they saw — but only in these 21 guys.
Analysis score
Maximum 90 for a randomized controlled trial.
Where the score came from
This study tested how caffeine affects your brain waves and heart while you sleep, using a special pill that releases caffeine slowly.
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 566 / 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.
- 1Even though caffeine made the heart more relaxed during sleep, it still disrupted the deepest, most restorative brain activity needed for good sleep.
- 2Caffeine made deep sleep brain waves drop when blood levels were above 7.4 μmol/L, slowed heart rate by about 3.2 beats per minute above 4.3 μmol/L, and increased a heart signal linked to relaxation above 4.9 μmol/L.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
Journal of Sleep Research
Year
2023
Authors
D. Baur, Dario A Dornbierer, H. Landolt
Related Content
Claims (4)
In healthy young men, consuming caffeine shortly before sleep increases a specific measure of heart rate variability during deep sleep stages, and this effect becomes significant when caffeine levels in the blood exceed about 4.9 μmol/L.
In healthy young men, taking 160 mg of delayed-release caffeine reduces low-frequency brain wave activity during deep sleep, and this reduction becomes significant when caffeine levels in the blood exceed 7.4 micromoles per liter.
When healthy young men consume caffeine shortly before sleep, their heart rate during sleep decreases by an average of 3.24 beats per minute, and this reduction becomes measurable when caffeine levels in the blood exceed 4.3 micromoles per liter.
Consuming caffeine within six hours of bedtime reduces the total amount of sleep and decreases slow-wave sleep.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.