Graveyard duty

Pro-circadian night shift

Here’s the TLDR first for this post, then cruise through for more detail:

1. Circadian Lights: dimmer, lower, amber - ideally maintaining alertness but also allowing some pineal melatonin to still flow. Amber blue blocking glasses, billed hats, hoods, turtlenecks and clothing that blocks light from the skin work as an alternative, but the gold standard is to tune the environment—a community effort!

2. Circadian Meals: daytime only, and if at night, ketogenic fat and protein because of the body’s reduced tolerance for carbohydrates in the dark

3. Circadian Team Building: work with your team to improve the environment, and ideally, get people on board with sharing the duty so everyone who works night has a schedule that allows them some time to sleep that overlaps the natural darkness (ie, each shift should ideally be less than 12 hours and the shorter the better)

From a circadian perspective, pretty much everything about today's graveyard shift is wrong. It is well-known now for causing cancer, metabolic problems, and many other woes. The effects are so diverse! Researchers lately are beginning to elucidate circadian entropy as a potential root cause/solution.

If you'd like more history and context, check out:

Epigenetics and light at night🚨

Toward a Circadian Night Shift

We have always had night-duties. They are part of human history and success. In fact, we are born needing care throughout the day and night. Night watch is natural.

In nature, sleep varies along with natural conditions.

With that being the case, you may wonder: if night work is natural, why do we need to fix it? It turns out, the challenges for night shift workers are the same as for the rest of us, only more extreme.

Here are the three thing we could change now to correct the impacts of night work on circadian rhythms:

1. Circadian-effective Lights

2. Daytime Meals

3. Cooperative Team Building

Circadian Lights for Night Shift

Circadian lighting in hospitals allows patients to rest at night, while allowing staff enough light to perform their duties.

Before electric lights, people with night duties had to make do with dimness. They had the moon (sometimes), stars, and flame lights (either candles or lamps). Our eyes are capable of adjusting to dim light over time, but in our electrically-lit world, we rarely do.

While brighter lights can make us feel safer at night, they come at a great cost. Neither the moon nor candles disturb melatonin; electric lights suppress it by 20-100% depending on the person¹. Low levels of melatonin are implicated in adverse outcomes across the lifespan². It is one of the most highly-distributed hormones in our body, meant to be present in almost every cell.

Some night shift workers are able to sustain a high level of melatonin at work. Others, no matter how long they have to "adjust" to the schedule, remain with low levels of melatonin at work. One way we could help our night crews would be to dim the lights and keep melatonin levels higher for everyone.

Circadian Food for Night Shift

No matter what schedule a person keeps, local sun time is the primary driver of circadian rhythms³. For shift workers, this comes into play as they are spending more energy during the "off" hours.

After 1 week of late eating, lean women show metabolic patterns more similar to the metabolic patterns of obese women.

Like all circadian systems, the digestive system has two modes. It likes to digest during the day, and fast during the night⁴.

Shift workers need energy to work, but they should be aware that digestion isn't the same at night. At night, the body has less ability to digest carbohydrates. In scientific literature, they say "reduced glucose tolerance." Newer studies are coming out to see what happens when night shift workers fast at night and eat during the day. It turns out, this may help correct their blood sugar⁵! This could help bring down the rates of obesity and other metabolic disorders among those with night shift duties. Alternatively, for those who absolutely must eat at night, choosing high-protein/healthy-fat foods at night could also help.

Circadian Teams for Night Shift

According to research by the Navy, it takes 4-6 people to cover a 24-hour period.

In circadian schedules, work/rest cycles add up to a 24 hour day. Shorter shifts covered by more people improves safety and performance. Longer hours and fewer people should be a short-term solution only for the time it takes to get enough qualified people.

Currently, most night shift schedules have day people and night people. The Navy has a very different approach that prevents circadian disruption. In their circadian-based schedules, everyone works day and everyone shares the night watch. How does it work?

Everyone works a short day shift (between 4-6 hours). Additionally, everyone comes in for a short night shift (2-4 hours). This allows everyone at least 6 hours of sleep that overlaps the natural darkness. This is key, because, as you remember, local sun time sets everyone's circadian rhythm.

To see examples of circadian watchbills, see:

Crew Endurance Handbook: A Guide to Applying Circadian-Based Watchbills

3.11MB ∙ PDF file

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A circadian-based watchbill is the term used for a work and rest schedule that conforms to a 24-hour day, allowing individuals to work, eat, and sleep at approximately the same time each day. When you combine the number of hours spent on watch with the number of hours off watch (whether doing other work, eating or sleeping), a circadian-based system will add up to 24 hours. The system aligns with the naturally-occurring 24-hour rhythm which drives all biological processes, down to the cellular level. Research conducted by the Crew Endurance Team at the Naval Postgraduate School over the past several years has demonstrated how circadian-based watchbills are superior to non-circadian watchbills in terms of crewmember preference and individual Sailor performance. This handbook is being provided to commanders and their staff to share some of the valuable lessons learned through scientific investigation and trial and error by other Naval commanders. It is not meant to be prescriptive but gives examples of some past watchbills that have been used effectively. For more information or to provide feedback, please visit the Crew Endurance website. http://my.nps.edu/web/crewendurance

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The benefits of circadian schedules are immense, but to me, the number one is safety. According to the Navy's research, schedules that disrupt circadian rhythms cause "worse-than-drunk" performance. This is NOT what I want to hear about doctors, EMTs, truckers, or other night workers. I can't see how convenience or higher wages could justify poor performance and long-term health challenges—especially when we CAN do better.

Summary of how to adapt night shift for stronger circadian rhythms

The main driver of circadian rhythmicity is the light/dark schedule; the second-most powerful driver of rhythmicity is meal-timing. So, the most important things are to create a circadian light environment and a circadian eating schedule. And the final piece of circadian night-shifts would be to learn from the Navy and start building circadian teams in a whole new way. Everyone should perform their primary work during the day, and everyone could come in for just a couple of hours at night. This last piece is a whole new paradigm! Wow. Here’s the summary again for pro-circadian night shifts:

1. Circadian Lights: dimmer, lower, amber - ideally maintaining alertness but also allowing some pineal melatonin to still flow

2. Circadian Meals: daytime only, and if at night, ketogenic fat and protein because of the body’s reduced tolerance for carbohydrates in the dark

3. Circadian Team Building: work with your team to improve the environment, and ideally, get people on board with sharing the duty so everyone who works night has a schedule that allows them some time to sleep that overlaps the natural darkness.

And here’s a post about just being a “wolf” archetype and enjoying nightlife, which might also be insightful (scroll to the end for more detail about the latest nightshift recommendations from the Navy):

Share with the Community:

Have you ever worked night shift? What was it like? Please login and tell us your story in the comments.

Or, head over to the community chat for questions and support with navigating night shift:

1. Cain, S., McGlashan, E., Vidafar, P., et al. (2020). Evening home lighting adversely impacts the circadian system and sleep.

2. Salavaty, A. (2015). Carcinogenic effects of circadian disruption: an epigenetic viewpoint.

3. Roenneberg, T. and Merrow, M. (2007). Entrainment of the Human Circadian Clock.

4. Ma, D., Li, S., Molusky, M., and Lin, J. (2012). Circadian autophagy rhythm: a link between clock and metabolism?

5. Chellappa, S., Quian, J., Vujovic, N., et al. (2021). Daytime eating prevents internal circadian misalignment and glucose intolerance in night work.

All material contained in this newsletter is for informational purposes only. This information is not intended to diagnose, prevent, or cure any medical conditon, nor to replace medical advice offered by qualified health care providers. Any application of the material provided is at your own discretion and is your own, sole responsibility.