Abstract
Background: Poor sleep can have a detrimental effect on the mental and physical health of adolescents. Currently, in New Zealand, 14.3% of adolescents sleep for more than nine hours, while 15.1% sleep for less than seven hours well below the sleep duration recommended for this age group. Furthermore, 56% of adolescents in NZ have poor sleep quality with higher prevalence in females (63%) than males (45%).
Objective: The primary objective of this study was to examine whether sleep characteristics (sleep duration, sleep onset, sleep offset and wake after sleep onset) are affected by evening consumption of caffeine containing beverages and the timing of food intake during the evening period within the adolescent population in Dunedin, New Zealand.
Design: The Measurement of Sleep, Screen use, Nutrition and Activity using Photo Images in Teens (SNAP IT) is a cross-sectional observational study of adolescents aged 13-17 years-old, conducted in Dunedin of New Zealand between November-December 2017 and February-May 2018. A total of 47 participants aged between 13-17 years were recruited to take part in this study. Participants wore an actigraph (GT3X+) on their non-dominant wrist for seven consecutive days and night to measure sleep characteristics (sleep duration, sleep onset, sleep offset and wake after sleep onset). Participants also wore an automated camera on a lanyard around the neck from 5pm to bedtime for three evenings to measure caffeine containing beverages and timing of food intake.
Results: The results from this study showed that there was no evidence of an association between sleep characteristics in participants who ate after 9:30pm compared to those who ate before 9:29pm (P>0.05). Participants who consumed meals before 7:29pm had a later sleep onset compared to participants who consumed meals after 7:30pm (P=0.03). When exploring caffeinate beverage consumption there was no significant difference in the sleep characteristics between participants who had caffeinated beverages (including tea and caffeinated soft drinks) in the evening period to those who did not have any caffeinated beverage (P>0.05). However, when their usual evening intake of caffeine containing beverages (interviewer administered questionnaire) was used to compare to sleep characteristics, participants who reported drinking usual caffeinated beverages and hot chocolate in the evening had a later sleep onset compared to those who reported not drinking any caffeinated beverages (P=0.02).
Conclusion: Due to the limitations of this study there was no conclusive evidence of an association between the timing of food intake and caffeine intake and sleep outcomes. However, when intake of caffeinated beverages was examined by a questionnaire, there was a significant association between usual caffeine intake and later sleep onset. Improvements for future research could include; using the camera alongside a weighed food record, or the creation of a health index for measuring the quality of meals to examine more closely the types of food consumed. These may assist in investigating the link between pre-sleep eating and sleep outcomes in adolescents.