Resetting the late timing of 'night owls' has a positive impact on mental health and performance.
AI Summary
This randomized controlled trial investigated whether practical interventions could help 'night owls' shift their natural late sleep patterns earlier to better align with societal schedules. Researchers used non-pharmacological interventions targeting light exposure through earlier wake-up and sleep times, along with fixed meal times, caffeine timing, and exercise. The study found that participants successfully advanced their sleep-wake timing by approximately 2 hours, as measured by both activity monitors and biological markers including melatonin onset and cortisol awakening response. Importantly, this shift didn't reduce total sleep duration. The timing changes were accompanied by significant improvements in self-reported depression and stress levels, as well as better cognitive performance (faster reaction times) and physical performance (improved grip strength) during morning hours when night owls typically perform poorly. The study suggests that strategic light exposure and lifestyle interventions can help people with naturally late chronotypes adapt to conventional schedules while improving both mental health and performance outcomes.
Key Findings
- Participants achieved a significant 2-hour advance in sleep-wake timing using light exposure and lifestyle interventions
- The timing shift was confirmed by biological markers including dim light melatonin onset and cortisol awakening response
- Improvements included reduced depression and stress levels along with better morning cognitive and physical performance
- Sleep duration remained unchanged despite the earlier timing shift
Abstract
There is conflict between living according to our endogenous biological rhythms and our external environment, with disruptions resulting in negative consequences to health and performance. This is often documented in shift work and jet lag, but 'societal norms' (eg, typical working hours) can create profound issues for 'night owls', people whose internal biological timing predisposes them to follow an unusually late sleep-wake cycle. Night owls have also been associated with health issues, mood disturbances, poorer performance and increased mortality rates. This study used a randomized control trial design aimed to shift the late timing of night owls to an earlier time (phase advance), using non-pharmacological, practical interventions in a real-world setting. These interventions targeted light exposure (through earlier wake up/sleep times), fixed meals times, caffeine intake and exercise. Overall, participants demonstrated a significant advance of ∼2 h in sleep/wake timings as measured by actigraphy and circadian phase markers (dim light melatonin onset and peak time of the cortisol awakening response), whilst having no adverse effect on sleep duration. Notably, the phase advance was accompanied by significant improvements to self-reported depression and stress, as well as improved cognitive (reaction time) and physical (grip strength) performance measures during the typical 'suboptimal' morning hours. Our findings propose a novel strategy for shifting clock timing towards a pattern that is more aligned to societal demands that could significantly improve elements of performance, mental health and sleep timing in the real world.
Authors
Elise R Facer-Childs, Benita Middleton, Debra J Skene, Andrew P Bagshaw