The Helpful Activities Before It is Time for Bed (HABITS) Study: The effect of food, physical activity and screen time on sleep in children

Advisory groups worldwide endorse a range of behaviours, collectively known as ‘sleep hygiene’, which are thought to promote good sleep health. These behaviours include sleep habits, environments (e.g. bedding, temperature and noise), and pre-bed behaviours. However, the evidence base illustrating that each of these strategies actually influences sleep in children is poor, particularly those recommendations focusing on restricting the use of electronic media, vigorous exercise, or the consumption of food in the hour before bed. HABITS is a randomised crossover trial that will investigate whether undertaking these behaviours influences sleep that night. Following a baseline week to measure 'usual' sleep (bedtime, sleep duration and sleep quality), participants will be randomised to the order in which they complete four conditions over four weeks. Condition 1 (No week - the comparison or ideal week): Avoid screen use and physical activity and do not have any food in the hour before bed. Condition 2 (Screens week): Use screens for at least 30 minutes in the hour before bed (but restrict physical activity and do not have any food). In this context, screens include television, computers, phones, tablets, gaming consoles and all other digital devices. Condition 3 (Exercise week): Be physically active for at least 30 minutes in the hour before bed (but restrict screens and do not have any food). In this context, physically active refers to moderate to vigorous PA. Predicted max heart rate (HR) will be estimated using the Tanaka equation (MHR = 208–0.7*age) https://www.tandfonline.com/doi/full/10.1080/02701367.2019.1615605) and participants will be asked to aim for the CDC recommended % HR values for moderate activity (65% predicted Max HR) as the minimum level to target during the exercise intervention. This will go alongside video footage that will confirm that the participants engaged in PA. Condition 4 (Eat dinner week): Eat dinner in the hour before bed (but restrict screens and physical activity). No minimum number of calories will not be set; however a trained dietitian will assess the participants usual “meal time” food intake collected at the baseline appointment, and make recommendations to the family around how much food would be considered acceptable. Participants will be able to move their dinner meal into the hour before bed, and if this is not possible, the researchers will give the participant and the caregiver a list of options that would an appropriate amount of food, to ensure adherence. Families will be asked to follow each intervention condition on the same consecutive three days of each intervention week (days 5-7). These 3 days will provide enough data to determine how each behaviour influences sleep, while allowing a washout between each condition (in case the behaviours do impact sleep) and limiting participant burden. As we are examining the effect of the condition on sleep the same night, this amounts to three observations per participant per condition, which should give more reliable estimates than just one observation per condition. Each family can choose what days of the week are days 5-7 for them, as long as the same days apply across all five weeks. All interventions will occur during the school term to limit known changes in sleep caused by holidays and the time around daylight savings will be avoided. Information and details about the interventions will be delivered by trained researchers, through face-to-face appointments at the participant's home, but parents will play a role in administering the interventions as well. Adherence to each intervention condition (on days 5-7 of each experimental week) will be measured using wearable video cameras from 90 minutes before usual bedtime until the child goes to bed. The cameras go on 90 mins before and not 60 mins in order to account for potential variation in actual bedtime relative to usual bedtime. These cameras are worn on chest harnesses, facing outwards and capture what activities the child is engaging in. Video footage will be analysed to measure adherence as follows: Condition 1: Children use screens and engage in physical activity for less than or equal to 5 mins and do not consume food in the hour before bed. Condition 2: Children spend at least 30 mins on screens in the hour before bed (and engage in physical activity for less than or equal to 5 mins and do not consume food). Condition 3: Children spend at least 30 mins being physically active in the hour before bed (and use screens for less than or equal to 5 mins and do not consume food). Condition 4: Children consume their dinner meal in the hour before bed (and use screens and engage in physical activity for less than or equal to 5 mins). Sleep will be measured using waist-worn accelerometers at baseline and during each intervention week. Sleep latency will be measured using a second video camera placed in a tripod in the child's bedroom. This camera will capture when the child goes to bed, stops using any props (e.g. books) and attempts to go to sleep.