PROJECT SUMMARY
Shift workers experience profound circadian disruption, which can have deleterious long term effects on their
health and quality of life. Due to the necessity of night shift work for 24-7 continuous operations and safety, it is
urgent that society prioritize ways to support shift worker health. Mood, fatigue, and performance can be
improved in shift workers by shifting the timing of production of the hormone melatonin outside the hours they
are expected to work. This can be achieved with a targeted lighting intervention, as light is the primary input to
the body’s circadian clock, and supported by behavioral interventions, including meal and exercise timing.
Crafting such an intervention for an individual, however, requires knowledge of the person’s current
biological time, or circadian state, which has traditionally been extremely challenging to assess in shift workers.
The gold standard measure of circadian timing is dim light melatonin onset, or DLMO. For day workers, DLMO
most commonly occurs in a six hour window prior to habitual bedtime. For fixed night shift workers, however,
DLMO can occur anytime over the 24-hour day. This requires 24 hours of melatonin collection in order to arrive
at a single indicator of internal time, which is often prohibitively time consuming and expensive.
The small business on this proposal, Arcascope, has developed new techniques for noninvasively
predicting circadian timing through consumer wearable devices (e.g. Apple Watch) in collaboration with
research partner organization Henry Ford. These techniques can accurately predict DLMO timing in shift
working adults using consumer wearable devices. The PIs of this grant have also developed mathematical
techniques for generating lighting recommendations based on predicted circadian timing, aimed at shifting the
peak circadian drive to sleep outside the window of working hours. These techniques have been evaluated in a
Phase I STTR, through the deployment of an iOS mobile app, SHIFT, which achieved large phase shifts in real
world night shift workers, demonstrating that it is possible to shift their circadian rhythms so that the melatonin
secretion occurs outside their working hours.
The next step in this work is to move beyond feasibility and towards effectiveness and implementation.
In particular, it remains to be demonstrated that the mobile app can produce meaningful changes in
stakeholder-centered outcomes in large, rigorously tested cohorts. These outcomes include not only worker
health outcomes, such as depression and sleep health, but also quantities of critical import to their employers
finances, including worker turnover, safety, and health coverage costs. In this Phase II project, we propose to
evaluate how the SHIFT app can affect these outcomes, demonstrate noninferiority of an Android version, and
assess key facilitators and barriers to engagement and implementation.