Caffeine, a common stimulant found in coffee, tea, and energy drinks, can significantly disrupt sleep, even when consumed hours before bedtime. A recent study published in Sleep examined the effects of different caffeine doses consumed at various times of the day on sleep quality. The findings suggest that higher doses of caffeine can negatively impact sleep even when consumed up to 12 hours before going to bed.
The study involved 23 men aged 18 to 40 with moderate habitual caffeine intake (under 300 mg daily). Participants were given either a 100 mg dose (typical) or a 400 mg dose (high) of caffeine in the morning, afternoon, or evening. Researchers used in-home sleep monitoring devices and sleep diaries to track sleep patterns over a 21-day period. Women were excluded from the study to control for hormonal variations.
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Results showed that while a 100 mg dose of caffeine consumed up to four hours before bedtime had minimal impact on sleep, a 400 mg dose significantly disrupted sleep even when consumed 12 hours prior. The closer to bedtime the caffeine was consumed, the greater the negative impact on sleep quality. The 400 mg dose affected sleep onset, total sleep time, and deep sleep duration, particularly when taken within four hours of bedtime.
Interestingly, participants’ self-reported sleep logs often did not align with the objective sleep data collected by the monitoring devices. This discrepancy suggests that caffeine drinkers may not accurately perceive how caffeine affects their sleep. This highlights the importance of consumer education regarding caffeine’s impact on sleep.
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According to study author Carissa Gardiner, a postdoctoral researcher at the SPRINT Research Centre at the Australian Catholic University, the study aimed to address the limited evidence available for recommending safe caffeine consumption times and dosages relative to sleep. Gardiner emphasized the prevalence of caffeine consumption and its potential contribution to widespread sleep insufficiency.
The study concluded that consuming 100 mg of caffeine up to four hours before bed is unlikely to significantly disrupt sleep. However, to minimize sleep disruptions, it’s recommended to avoid consuming 400 mg of caffeine within 12 hours of bedtime. Further research is needed to provide more comprehensive guidelines for caffeine consumption and sleep hygiene. Gardiner’s long-term goal is to continue building a stronger evidence base to educate consumers on minimizing caffeine’s impact on their sleep.
