Biphasic sleep – the best thing since sliced bread?
Thank you to John Bullock for forwarding this excellent article from the BBC about sleep and shift workers – The hidden cost of the night shift and how to sleep it off. It talks about new research into biphasic sleep (or sleeping in two ‘chunks’), suggesting that this may be an ancient pattern for health, and how planned naps could help people who work nights – or, like millions of parents and carers – simply dealing with the reality of fragmented nights – to cope.
Large-scale biobank studies suggest associations between regular patterns of bright days and dark nights, quality and quantity of sleep and pretty much every dimension of performance, longevity and quality of life. The WHO has classified disruption to the body clock as a probable carcinogen in humans.
Perhaps unsurprisingly, studies that compare patterns of activity and rest in communities before and after the introduction of electric lighting point to significant shifts, including increasing individual variation or drift away from the natural distribution of sleep and wake times and increased daytime naps. Interestingly, these studies don’t suggest widespread biphasic strategies where significant numbers of the community are up and about in the middle of the night – Sleep timing and duration in indigenous villages with and without electric lighting on Tanna Island, Vanuatu.
This confirms a fascinating article in the Lancet that concludes that while historical references to biphasic sleep may be a valuable lens through which to view philosophical ideas about inspiration and connection with other realms, scientific evidence suggests that a single, consolidated block of sleep is the most efficient way to give the body and brain the opportunity to build, repair and recover – Have we lost sleep? A reconsideration of segmented sleep in early modern England.
But if we think of biphasic sleep as segmented sleep- perhaps a longer stretch followed by a nap, and shifts as anything that gets in the way of a ‘standard’ night in bed, there’s plenty of evidence that an intentional approach to lighting could help.
The evidence is split into two broad domains – acute, usually focused on alerting effects; longer-term interventions focused on circadian or body clock-setting strategies.
When it comes to acute effects, a number of projects with truck drivers, including this one in Arctic winter conditions suggest that a daylight supplementing lighting panel installed in the cabin, can improve alertness, driving performance and sleep – Multimodal in-vehicle lighting system increases daytime light exposure and alertness in truck drivers under Arctic winter conditions. Another with young drivers found that bright light was as good as a cup of coffee, but subjective alertness was best when the two were taken together – Bright light alone or combined with caffeine improves sleepiness in chronically sleep-restricted young drivers.
There’s growing evidence that it’s the pattern of light exposure rather than the light levels themselves that count for reliable, sustained impact, with a dose-response curve that links higher light levels in the earlier part of the day with our ability to cope with exhaustion – A higher illuminance reduces momentary exhaustion in exhausted employees: Results from a field study. More light during the day is also likely to help us cope with light and screen time after dark – From Sunlight to Screens: Modeling When Light Exposure Matters Most for Sleep and Circadian Health.
So, even if you’ve had a sleepless night, getting outside, or finding a brightly-lit space for as little as 30 minutes first thing in your day could deliver the fast-charge your brain so desperately needs to keep you safe – Alerting effects of light in healthy individuals.
A power nap just as good when it comes to boosting cognitive performance, feeling happier and more alert – anything between 30 and 50 minutes, ideally before 1pm is optimum to get the benefits without the jet lag feeling – Effects of a Short Daytime Nap on the Cognitive Performance: A Systematic Review and Meta-Analysis.
Using light to set the body clock is obviously more complicated, especially for people serving rotating shifts or working long-haul flights with short turnaround times: should you encourage them to stay on the same time zone or speed up the shift? And how alert do they really need to be?
Studies in closed environments designed to mimic submarines and other extreme environments suggest that ‘dynamic’ lighting that delivers the levels needed to set the body clock can stabilise the sleep-wake cycle with sustained benefits for cognitive performance and mental health – The effects of dynamic daylight-like light on the rhythm, cognition, and mood of irregular shift workers in closed environment. Others suggest that bright morning light can effectively shift the natural release of melatonin- an indicator of circadian entrainment by up to two hours in a single 24-hour cycle – Effects of Melanopic Equivalent Daylight Illuminance on Sleep Regulation and Chronotype-Specific Responses in Young Adults.
My experience working in residential care suggests that ‘quiet wakefulness’ delivered by soft, warm night time conditions can help teams to wind down and fall asleep when they get home and cope with rapid changes in shift timing.
Chronotype counts too, with growing evidence from nursing that night owls find it much harder than early birds to cope with the fragmented sleep caused by shift work and are most likely to suffer from burn-out, leading to higher risk of quitting early in their career. These insights have implications for anyone who cares about the future of this vital profession – Chronotype prior to shift work influences outcomes: resilience as a mediator of sleep and mental health.
Bottom line.
Very few of us will can count on the luxury of unbroken nights in a safe, cool and dark space. So embracing the principles of segmented sleep makes perfect sense – especially as the article points out, anxiety about not sleeping enough compounds the issue.
Intentional use of lighting could help.
If you need to power through, find some bright, cool light – and grab a coffee on the way.
If you can carve out 30 minutes for a power nap, find a quiet corner with ambient lighting to reduce your risk of falling into those deeper sleep stages that can leave you feeling groggy and get in the way of restorative sleep when that chance finally comes. If you’ve got time for a longer block of rest – ideally leave enough time to give your brain four or five full cycles at 70 – 120-minutes a piece, make sure it’s as dark as possible, quiet and cool – Physiology of Sleep.
October – it’s just around the corner…
The Care Show is just 12 weeks away – it’s become one of the best places to gauge the temperature of the sector, try out new tech and hear from leading lights and people at the coal face. At the strategic level, I’m looking forward to hearing what Chris Badger, chair of the Care Quality Commission and Lord Hunt of King’s Health have to say. I’m keen to hear Kieran Gill of Azure Care talk about building trust with private clients and will be in the front row for for Muhammad Qureshi’s session. as Head of Compliance & NIHR Homecare Research Champion, he’s going to be talking about evidence-led care.
I’m also privileged to be sharing latest research and current circadian lighting projects on the 8th of October on the Design and Build stage.
Hope to see you there!