The Study
Caffeine intake from different dietary sources and its association with sleep quality in employed adults
This study found that people who drank more caffeine tended to sleep worse, but it didn't watch them over time to see if the caffeine made them sleep worse or if they drank more caffeine because they were already sleeping poorly. So we can't say caffeine causes bad sleep—just that the two are linked.
Analysis score
Maximum 44 for a cross-sectional study.
Where the score came from
This study looked at adults who work and found that those who drank more caffeine (like coffee or tea) tended to sleep worse — they slept less and woke up more at night.
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 544 / 100
Quality score
Snapshots of a population at a single point in time, or descriptions of small groups. Can identify correlations and prevalence, but cannot determine cause and effect.
Key takeaways
Summary
Based on the study abstract and findings.
- 1Yes — over 7 in 10 working adults had poor sleep, and those who drank more caffeine had worse sleep, even after accounting for other factors like stress or exercise.
- 2On average, people drank 262.5 mg of caffeine daily.
- 371.7% had poor sleep.
- 4Higher caffeine intake was linked to shorter sleep and more nighttime waking.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
BMC Nutrition
Year
2026
Authors
Kadriye Toprak, Zeyneb Yıldırım, Feride Ayyıldız
Related Content
Claims (6)
Consuming caffeine in the afternoon or evening reduces sleep quality.
Among employed adults, black coffee provides the largest share of daily caffeine intake at 23.9%, followed by black tea at 21.8% and Turkish coffee at 12.5%. The total caffeine exposure is determined by the type of beverage and its caffeine concentration, not merely how often it is consumed.
When employed adults consume caffeine during the day versus later in the evening, their sleep quality differs.
Adults who consume more caffeine tend to sleep less and experience more sleep disturbances, even when accounting for differences in age, gender, education, physical activity, and chronic health conditions.
Adults aged 19–50 who consume about 262.5 mg of caffeine daily have worse sleep quality, shorter sleep duration, and more nighttime awakenings compared to those with lower intake.
Among working adults, 71.7% have poor sleep quality based on standard measurements, a rate higher than the 15–50% seen in the general population.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.