The Dose and Timing Relationship Between Caffeine and Subsequent Sleep Quantity and Quality

Intervention is the administration of caffeine to be taken orally in capsule form. The study is a crossover design where each participant will be randomly exposed to all seven conditions organised using a Latin Square design. Each condition will be separated by a 2 day washout period. Conditions include; Placebo 100mg administered 12 hours prior to bedtime 100mg administered 8 hours prior to bedtime 100mg administered 4 hours prior to bedtime 400mg administered 12 hours prior to bedtime 400mg administered 8 hours prior to bedtime 400mg administered 4 hours prior to bedtime Participants will consume three capsules on each experimental day at 12, 8 and 4 hours prior to bedtime. The caffeine capsule will be administered at the timepoint and dose relevant to the condition with the remaining two capsules containing the placebo. All three capsules will contain the placebo for the placebo condition. Saliva samples will be collected using cotton chew swabs to monitor caffeine concentrations and compliance. These will occur on experimental days at 11, 7 and 3 hours prior to bedtime, 5 minutes prior to bedtime and 5 minutes after waking.