O050 The Dose and Timing Relationship between Caffeine and Subsequent Sleep

INTRODUCTION: There is currently a lack of evidence to guide recommendations for the consumption of caffeine to mitigate its effects on sleep. Therefore, the aim of this study was to investigate the effect of caffeine dose and timing combinations on subsequent sleep. METHODS: Twenty-three healthy adult males with a moderate habitual caffeine intake (<300mg/d) participated in a randomised, repeated-measures study. Participants completed seven conditions, including a placebo and two caffeine doses (100mg and 400mg) consumed at three different time points (12, eight, and four hours prior to habitual bedtime) with a 48-hour washout period. Sleep was measured using in-home partial polysomnography and subjective sleep diaries. Linear mixed effects models were used to estimate the effect of each caffeine condition on sleep characteristics. RESULTS: Caffeine negatively impacted sleep when compared to the placebo. The largest impact was observed when the highest dose of caffeine (400mg) was consumed closest to bedtime, with a 54.0 minute reduction in total sleep time (p=<0.001), a 10.2% reduction in sleep efficiency (p= <0.001), a 14.4 minute increase in sleep onset latency (p=0.047), a 25.3 minute increase in wake after sleep onset (p=<0.001), a 5.5% increase in the proportion of light sleep (N1&N2)(p=0.029), and a 4.55% reduction in deep sleep (N3)(p=0.026). DISCUSSION: The largest decrements in sleep occurred when caffeine was consumed at a high dose in close proximity to bedtime. These findings highlight the importance of considering the amount and timing of caffeine intake when aiming to minimise the effect of caffeine on subsequent sleep.