The purpose of this study is to examine the effectiveness of a personalized light exposure schedule for Shift Work Disorder (SWD) in night shift workers compared to a non-personalized light exposure schedule.

Participants will be randomized into each condition (n = 25) in a 1:1 ratio. Variables of interest, dim light melatonin onset (DLMO) and shift work disorder (SWD) symptoms, will be assessed before and after the intervention, which will last two weeks. All participants (N=50) will be asked to wear an Apple Watch for two weeks leading up to an in-lab visit. Activity data collection from the Apple Watch will be processed through a mathematical model of the human circadian pacemaker (previously validated in SWD) to generate estimates of DLMO. This two-week period is followed by a 27-hour laboratory visit for pre-treatment assessment of DLMO (hourly saliva melatonin samples over 24 hours). At the end of this visit, participants will receive an orientation to the SHIFT mobile application, where they will be able to assess their prescribed light exposure schedule.

Inclusion Criteria:

• Participants must work at least 2 night shifts a week
• Participants must have night shifts starting between 18:00 and 02:00 and lasting 8 to 12 hours
• Participants must have maintained this night shift schedule for at least 6 months
• Participants must have Shift Work Disorder, diagnosed based on ICSD-3 criteria

Exclusion Criteria:

• Medical history of central nervous system disorders
• Medical history of other sleep disorders
• Diagnosis of an unstable major medical condition medical chart review
• Dependence on alcohol (≥ 4 beverages a day)
• Heavy tobacco use (≥ 10 cigarettes per day)
• Recreational drug use
• Use of medications impacting central nervous system functioning
• Caffeine use in excess of 5-6 servings (~ 600mg) per day
• Pregnancy

Request for data sharing will be evaluated on a case-by-case basis.