O008 Temporal Associations between Sleep and Caffeine Consumption in Young Adults

Abstract Aims Laboratory studies suggest that caffeine consumption has clear and consistent adverse effects on sleep, but epidemiological studies have yielded mixed findings. This study aimed to examine temporal associations between sleep and caffeine consumption in young adults. Methods Fifty-one New Zealand young adults (aged 18-25 years) wore an actigraph and completed a sleep diary for 7 days to capture objective and self-reported measures of sleep and self-reported caffeine intake, providing 355 observations. Mixed linear models were conducted to assess temporal associations between caffeine intake (dose and timing) and the subsequent night’s sleep. Lagged models were conducted to assess temporal associations between sleep characteristics and next-day caffeine dose. Independent variables for caffeine and sleep were included in models as within-person and between-person variances from the mean. Results Between participants, those who consumed more caffeine per day than the group average had shorter total night time (β=-0.12; p=0.02) and daily (β=-0.12; p=0.02) sleep durations in the subsequent sleep period(s). Conversely, between participants, those with shorter night time (β=-0.06; p=0.004) and daily (β=-0.06; p=0.01) sleep durations consumed more caffeine in total the following day. Within participants, on days with longer night time (β=0.07; p=0. 001)and daily (β=0.05; p=0.02) sleep durations than their personal average, they consumed more caffeine the next day. Conclusion There may be a cycle of activity in young adults whereby higher caffeine consumption leads to shorter sleep, which leads to higher caffeine consumption. Further research that accounts for prior sleep history is needed to elucidate associations with sleep characteristics.