In researching this question, the most recent and comprehensive piece of evidence I could find was a systematic review of thirty-five randomized controlled trials (RCTs) published in 2014. 1 The researchers concluded that melatonin shows promise to prevent phase shifts from jet-lag, and can promote better sleep in persons with insomnia, as well as healthy adults.
However, one population was glaringly omitted from their recommendations; shift workers (specifically night shift workers). Read on to find out why this may have been the case and why I believe melatonin is still a useful tool for shift workers.
Supplemental melatonin for daytime sleep promotion
Within this review, all of the high quality studies on night-shift work found little to no benefit of melatonin when compared with a placebo.
This could be a result of other circadian synchronizers, such as the light, that normally work in harmony with melatonin, now working against it. Also, melatonin merely acts as a signal, telling the body that it’s time for sleep, and has little effect on sleep itself. It will still be a challenge for the body to generate quality sleep at this unnatural time.
However, there are other things we must look at before writing off melatonin as a tool for promoting day time sleep.
It is not clear from the studies how much emphasis was placed on limiting the effect of other circadian cues. For example, the use of blue-light-blocking glasses, blackout blinds
In fact, one of the “high quality” studies went so far as to provide thirty minutes of bright light exposure before sleep to simulate the sunlight exposure of driving home from work. 2 The goal was to prevent phase delays in circadian rhythms so that any improvement in sleep was attributable solely to the melatonin. Useful for the purpose of the study perhaps; not so much for the shift worker trying to optimize sleep.
Light is a stronger circadian regulator than exogenous melatonin. 3 It’s not at all surprising that melatonin was ineffective under these circumstances.
On a related side note, it has also been shown that timing both bright light and melatonin to phase advance can produce a larger phase shift than either on its own. 4
Given that light is the biggest synchronizer of circadian rhythms, controlling light exposure is priority number one. Only after light is optimized should you consider supplementing with melatonin.
As with most everything in science, more rigorous studies are needed to draw any hard conclusions about melatonin’s effectiveness in promoting daytime sleep.
The length of your time on night shift - another important factor
“If melatonin is used for daytime sleep promotion, unwanted circadian phase shifts could occur” 1
The human body adapts slowly to changes in shift schedules, generally taking one day to adapt to each hour change. Even when implementing every known strategy and timing everything perfectly, shifting your internal clock three hours in one day is about the most you can hope for.
As such, melatonin may cause more harm than good for shorter night shift rotations.
My opinion on the use of melatonin for facilitating day time sleep
In light of this information, I do not currently use melatonin to help with daytime sleep.
I work a rotating shift schedule with an even split between day shifts and night shifts. When you factor in days off, I’m trying to sleep at night far more than I’m trying to sleep during the day. Working more than four night shifts in a row is an extremely rare occurrence. Taking this into account, I don’t want to risk any “unwanted circadian phase shifts” making it more difficult to switch back to a normal routine.
If, however, I worked night shifts permanently, or a schedule requiring many night shifts in a row – some jobs have rotations measured in weeks or months instead of days – I would consider melatonin as a means of adjustment. Though I would first concentrate on optimizing other factors; most notably light.
Melatonin use for switching back to day shift
I think the abstract of this paper is slightly misleading.
“Based on the literature to date, no recommendations for use in shift workers . . . can be made at this time.” 1
This statement fails to account for rotating shift workers or night shift workers looking to return to a dayshift schedule.
Melatonin can help normalize circadian rhythms. 5 When returning to a normal schedule after night shifts, other factors, such as light exposure, will be working in harmony with the supplement. This is essentially the same as recovery from jet-lag.
“circadian synchronizers such as bright light also promote phase adjustment to jet lag, while they promote no adjustment to night-shift work”. 6
Closing thoughts
I don’t use melatonin on a regular basis, but I always keep it on hand. I’ll use it on occasions when I have to switch from night shift to day shift in a short time period, i.e., twenty-four hours.
On a couple occasions I’ve used it after waking up at night, unable to get back to sleep. Though caution is needed here as melatonin concentrations naturally peak around three to four a.m. and drop sharply shortly after. If sleep disruption occurs later in the night, I’ll forgo melatonin to avoid the risk of a phase delay and grogginess in the morning.
I don’t know how much may be attributable to the placebo effect, but I find I’m usually able to fall asleep quickly after taking melatonin. However, the resultant sleep is not always solid, sometimes leaving me tossing and turning during the latter portion of sleep.
Other points to consider before supplementing with melatonin:
- This is not medical advice. Talk to a healthcare professional before supplementing with melatonin.
- You need less than you probably think – 0.5 to 2 mg should be adequate. Start small and work your way up if needed.
- It should be taken only occasionally or for a short time period.
- It should not be taken with other sleep medicines or alcohol.
- The body’s natural melatonin production declines as we age. Older individuals may benefit from supplementing more regularly and taking higher doses.
Photo by Dmitry Bayer on Unsplash
- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4273450/[↩][↩][↩]
- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3679650/[↩]
- https://www.ncbi.nlm.nih.gov/pubmed/8963651[↩]
- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3841985/[↩]
- https://www.ncbi.nlm.nih.gov/pubmed/26568127[↩]
- http://www.ncbi.nlm.nih.gov/books/NBK3977/pdf/TOC.pdf[↩]