The Study
Caffeine Reduces Low-Frequency Delta Activity in the Human Sleep EEG
This study gave 8 young men caffeine or a sugar pill before bed and watched their brain waves. It found that caffeine changed their brain waves during sleep, but we can't say for sure it's the caffeine's fault because we don't know if they knew which one they got. So it's a good hint, but not a final answer.
Analysis score
Maximum 90 for a randomized controlled trial.
Where the score came from
Drinking coffee close to bedtime tricks your brain into thinking it's not time to sleep deeply.
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 541 / 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 — even a small amount of caffeine (like a cup of tea) can disrupt your deepest, most restorative sleep, even if you still fall asleep.
- 2Caffeine made it harder to fall asleep (longer sleep latency), reduced deep sleep by about 20% in the first sleep cycle, and increased brain spindles, but didn't fully block sleep.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
Neuropsychopharmacology
Year
1995
Authors
H. Landolt, D. Dijk, S. Gaus, A. Borbély
Related Content
Claims (6)
Consuming caffeine within six hours of bedtime reduces the total amount of sleep and decreases slow-wave sleep.
Caffeine increases the number of sleep spindles in the brainwaves of healthy young adult males during sleep, and this change is different from how caffeine reduces deep sleep waves.
A 100mg dose of caffeine taken at bedtime reduces delta brainwave activity during the first deep sleep phase in healthy young adult males, altering the natural pattern of deep sleep brain activity.
A 100mg dose of caffeine decreases deep sleep on the night it is consumed, but deep sleep returns to normal by the next night.
Taking 100mg of caffeine at bedtime increases the time it takes to fall asleep and decreases the percentage of time spent asleep while in bed for healthy young adult males.
Caffeine reduces deep sleep brain activity only during the first deep sleep period after consumption and does not affect deep sleep brain activity for the rest of the night.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.