Shift Work Disorder

What Exactly is Shift Work Disorder?

Shift work disorder, or SWD, is a type of circadian rhythm sleep disorder which is caused by working shifts that do not fall within the conventional working hours of around 9 am – 5 pm. These shifts overlap with periods of significant light sensitivity which can cause shift workers to be particularly vulnerable to having dysfunctional circadian rhythms.

What’s the difference between shift workers with and without shift work disorder?

The diagnostic criteria for SWD was established by the American Academy of Sleep Medicine (AASM) in 2005 and they include: (i) complaints of insomnia or excessive sleepiness associated with a recurring shift work schedule, (ii) symptoms that occur over the course of at least one month, and (iii) sleep log or actigraphic monitoring for at least 7 days demonstrating a circadian misalignment. If a worker meets all these significant criteria as well as some other minor ones, they will be diagnosed with SWD.

Generally, shift workers who are not diagnosed with shift work disorder may still struggle with many of the same sleep problems as their diagnosed counterparts. A majority of all people that have shift work schedules have some varying difficulty falling or staying asleep during the day and remaining awake during their shifts. The difference between shift workers without SWD and those diagnosed with SWD comes down to the intensity of the sleep problems that they experience and how significantly it impairs their functioning and routines.

Is Shift Work Disorder really a problem?

Nearly 20% of the full time working force in the US takes part in some type of shift work and an estimated one in five of all shift workers have experienced some type of shift work disorder.

Employees diagnosed with SWD normally experience symptoms of insomnia, sleepiness while awake, and difficulty staying asleep. These symptoms are often dangerous because they put workers at an increased risk of having on-the-job accidents due to excessive sleepiness. The effects don’t stop when you clock out: shift work disorder can contribute to hormonal imbalances, mood problems, and substance abuse.

However, even though most people have a hard time acclimating to a shift work schedule, there are people out there who find it naturally easier to engage in shift work as well as people who may find it nearly impossible. There is a vast amount of variability in people’s ability to sleep, with one known factor being changes in the coding region of the PER3 clock gene which regulates sleep and wakefulness. Essentially, the difference between people who can stay awake until 3am and function normally with only 6 hours of sleep and those who need a full 10 hours per night in order to do the same can probably be sourced back to this clock gene.

What does science say about SWD?

There is still a lot of work being done to determine the actual cause of the overall sleepiness and insomnia that is found in diagnosed workers, but as of right now, there is a hypothesis that associates SWD with some clear differences in melatonin secretion.

We also know that the nature of shift work necessitates being awake at times where the body is the least alert and asleep at times where the body is supposed to be the most alert. Thinking about SWD through the lens of circadian rhythms can help us understand why workers can have impaired performance during their night shifts due to sleepiness while still having a hard time sleeping when they get home during the day.

This blog post was written by Arcascope’s intern, Ali Abdalla. Thanks to Ali for contributing it!