It’s nearly the first day of winter and the shortest day of the year – my daily fight with my alarm as it painfully disrupts me has always been an issue, but it’s even worse lately, as it’s dark when I leave for work and dark again when I come home. Even after 5+ years working the same schedule, I never seem to meet that early morning blaring with anything but some groggy-eyed grumbling and stumbling out of my bed. Clearly I’m just not a morning person, but dark mornings are even rougher. The sun is the main influence on our daily sleep and wake cycles, so it’s no wonder the limited sunlight makes me want to do nothing but hit the snooze button.
But compared to the nearly 1 in 5 Americans who works a nonstandard schedule, I have it pretty easy. Permanent overnight work, on-call duty, and rotations are the norm in some professions, and a third of these workers might be diagnosed with shift work disorder (1), experiencing chronic insomnia or sleepiness while on the job despite having time (from a biological standpoint) to sleep during their days off. According to the American Sleep Association, in addition to obvious short term effects, shift work disorder is correlated with dangerous long term effects, including increased rates of heart and gastrointestinal diseases (as high as three times the national incidence rate when compared to the general population).
Healthy sleep and wake cycles are the result of a complex process, but melatonin (2), a hormone secreted by the brain’s pineal gland, appears to play a role in stimulating them and even adjusting them. It’s no secret that for years melatonin supplements have been marketed to promote sleepiness and to treat jet lag. But results from treating shift work disorder in a similar fashion are much less clear at this time.
The pineal gland resembles a pine cone (hence the name) but was once called
the “third eye.” Philosopher/mathematician René Descartes,
believing it was the connection point between intellect and the body,
called it the “principal seat of the soul.”
I reviewed several studies from the last ten years which looked at melatonin’s role in adjusting the circadian clock to treat shift work disorder, and results were quite varied. One of the biggest issues, as is often the case in psychological/sociological studies, is translating findings in a lab to real-life situations. If you’ve ever used melatonin to help tire you or to combat effects of jet lag (I’ve tried it as a sleep aid) and work alternating or nonstandard shifts, here is some interesting research to consider:
- Sharkey and Eastman (2002) controlled for variables in previous studies and to determine whether specifically timed dosing with melatonin could produce phase shifts in individuals who must adapt to the changes in sleep schedule often associated with shift work. In their placebo-controlled study, the investigators assigned 32 healthy young adults to receive either placebo or melatonin (0.5 mg or 3.0 mg), in double-blind fashion. The protocol followed a strict sleep-wake schedule in a combination of controlled and uncontrolled settings. Subjects were scheduled to sleep for 8 hours during fixed dark nighttime periods (the phase advance), before a baseline constant routine was established. Participants took either placebo or assigned melatonin dose during the first 4 days of the phase advance portion of the trial, and all participants took placebo on other study days. They spent the first simulated night shift in the laboratory, and the remaining 6 night shifts were spent at home. Analysis of results for sleepiness and mood scales, sleep logs, and core body temperature measurements indicated that melatonin did in fact produce larger phase shifts than placebo, supporting its use to adapt to nighttime work.
- Smith et al. (2005) studied the sleep-inducing effect of supplemental melatonin given in the mornings during 5 daytime sleep periods that followed simulated night shifts to determine if individuals could fall asleep more quickly and rest more soundly during the daytime after a night-shift. The 36 participants were either given melatonin or placebo, and kept detailed sleep logs throughout the study, estimating their total sleep time. Parameters such as measures of movement, brain activity, and sleep fragmentation were measured with various lab equipment and software tools. The investigators found that the melatonin did not produce any statistically significant increase in daytime sleep quality when compared to the placebo. They claimed however, that these results may have either been due to the fact that melatonin was given to most subjects when internal s melatonin levels were already elevated (think a sleep-hangover effect) , or due to a ceiling effect in sleep quantity (if all participants were excellent sleepers), thereby limiting melatonin’s potential true impact.
- Bjorvatn et al. (2007) conducted one of the first studies that assessed melatonin’s effectiveness in a real-world setting, on a population of night shift workers on an oil rig whose daytime and nighttime work schedules alternated weekly. Offshore oil rig workers were randomized and treated with bright light and either melatonin or placebo. The research team found that melatonin and bright light led to reports of a modest reduction in sleepiness and increased sleep time by about 15 minutes per day. However results were not statistically significant and smaller than the researchers expected. A major limitation of this team’s study is that it was only completed by 17 subjects, and such a small sample size tends to enhance variation, making a larger sample more appropriate. The field setting in this study not only restricted the study population size, but also limited controls for other potential confounding variables (gender, age, use of prescription medications, etc.).
These three studies demonstrate a serious trade-off in science: controlled simulations vs. real-life. Yet it’s almost always the case that controlled, in-lab effects need to be demonstrated before looking at real populations. It can be argued that each of these have just as much merit in the scientific community and to the population as a whole. These are just a few of the studies I examined, but it’s enough to show how varied the results are, and how findings can be due to a variety of factors.
Environmental light is the main controller of our innate patterns of sleep and wakefulness, and nearly 20% of the US population works a nonstandard schedule that involves adapting to a sleep pattern that conflicts with this normal rhythm. Poor sleep quality associated with such schedules compromises health, safety and quality of life. Research assessing melatonin use as a treatment for shift work disorder is a means to addressing this issue; over the past decade, many studies have attempted to evaluate its usefulness in both simulated and real-world settings.
It’s clear in looking at the blue (sleep response to light) and red (sleep response to
supplemental melatonin) curves above that although both have the ability to
influence our sleep patterns, we respond much more to light. That’s why bright light
manipulation is often helpful in preventing jet lag, timing of course dependent
on whether you’re traveling east or west.
(from http://www.ccjm.org/content/78/10/675.full )
A review of the recent literature describing melatonin’s effectiveness compared to placebo indicates that results vary in terms of statistical significance, but internal factors and external confounds that may have influenced their results. In short, more research needs to be done in larger populations to determine if melatonin is a potential treatment for shift work disorder. In the meantime, there are many other steps that can be taken to improve rest quality, ensure safety, and maintain an overall high quality of life. I found this article, from the Cleveland Clinic Journal of Medicine, to have some particularly useful information and a clear explanation of what happens when our internal clock is out of sync with the sun.
- Sharkey KM & Eastman CI. Melatonin phase shifts human circadian rhythms in a placebo-controlled simulated night-work study. Am J Physiol Regulatory Integrative Comp Physiol. 2002; 282:R454-R463.
- Smith MR, Lee C, Crowley SJ, Fogg LF & Eastman CI. Morning melatonin has limited benefit as a soporific for daytime sleep after night work. Chronobiol Int.2005;22(5):873-888.
- Bjorvatn B, Stangenes K, Oyane E et al. Randomized placebo-controlled field study of the effects of bright light and melatonin in adaptation to night work. Scand J Work Environ Health. 2007;33(3):204-215.