Personalised daily body-clock tracking and circadian light therapy retiming to improve sleep, performance, health and safety

Light therapy involves personalised recommendations around when to seek and when to avoid bright light exposure, from sunlight and artificial lighting, to help accelerate body-clock adjustments. Specific recommendations will depend on sleep-wake schedules and personal commitments, but typically includes the use of light therapy glasses (Re-Timer) worn for ideally 60 minutes (minimum 30 minutes) immediately upon waking, and this timing will change over treatment as body-clock timing adjusts to the desirable schedule. Bright light avoidance in the 2-3 hours before bedtime is also typically recommended, although there can be exceptions depending on individual circumstances. For the experimental group, the timing and duration of light therapy will be determined based on the participant's circadian rhythms (estimated from daily core body temperature minimum time, Tmin) and treatment goals (e.g., the number of hours they wish to shift their natural wake up time). All participants will have weekly in-person treatment sessions with registered sleep psychologists with a minimum of 3 years' experience at the Adelaide Institute for Sleep Health (AISH) clinic once a week to review treatment plan. Treatment sessions will take 1-1.5 hours. For most participants, the anticipated total duration of intervention will be 3-4 sessions, up to a maximum of 6 sessions (6 weeks), depending on sleep timing readjustment outcomes. This 6-session schedule fits with the General Practitioner (GP) Mental Health Care Plan (MHCP) referral structure, in which patients referred by their GP start with 6 sessions with a psychologist and then need a GP review to access the remaining 4 sessions in the same year (maximum 10 sessions within a calendar year). We will review participants' goals and adherence after 6 treatment sessions and the intervention should finish if these have not been met. In rare cases, this review may also help determine whether extending treatment beyond 6 weeks is clinically justified. During the study period, all participants (including the control group) will be asked to wear an array of wearable sensors and ingest core body temperature measurement capsules to measure key physiological markers and infer circadian rhythm timing estimated via core body temperature measurements. Before each treatment session, participants will ingest about three core body temperature capsules weekly and wear passive wearable sensors largely on their chest and wrist to collect key physiological information whilst completing their daily routines. Before each treatment session, participants will be asked to complete smartphone-administered cognitive performance tests each morning and evening. Prior to completing the daily cognitive performance tests, participants will complete the Positive and Negative Affect Schedule (PANAS-SF), a validated questionnaire to determine the dimensions of mood. Participants will be provided with MedBug, a mattress and bedside sensor and monitoring device developed by our team, to capture body position and breathing signals while asleep during each circadian assessment period. They will simply need to place MedBug on their mattress for data recording, with no worn sensors required for this device. After collecting the core body temperature data each week, a weekly report summarising these data for each participant in the experimental group will be made available to the psychologists before the upcoming treatment session. This report will include daily circadian, sleep, and light data to inform the psychologists on determining the timing of applying personalised daily Tmin adjusted light therapy for the following week. Participants are determined to have reached treatment endpoint when their average wake up time in the past 7 days as reported in their sleep diaries is within at least 80% of intended shift in wake up time. For example, if their natural wake up time is 2pm before treatment and preferred wake up time is 9am (intended shift in wake up time is 5 hours earlier), they will reach treatment endpoint when their average wake up time in the past 7 days is 10am or earlier (at least 80% of intended shift in wake up time, i.e., 4 hours earlier). Participants will also undergo pupillometry which is a measurement of pupil size and pupillary light reflex. This assessment will involve using either a handheld pupillometer or a desk-mounted pupillometer. The pupil may be measured in response to room lights, the device's inbuilt light source, or an external light source. Participants may be 'dark adapted' (asked to sit in a dark room with or without blackout goggles) prior to or between some of these assessments in order to standardise responses. Each assessment will be up to approximately 60 minutes. These are non-invasive measurements that hold no risk to participants other than minor discomfort from the pupillometer goggles sitting firmly on their face. Adherence to the intervention will be assessed on the basis of a) psychologist session attendance, b) light therapy glasses determined usage data (device on- and off-timing data), and c) light pin (MiEye device) data records.