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This study explored individual factors that contribute to risk of shift work disorder and particularly in the context of sleep hygiene.

Several surveys, including the Shift Work Disorder Questionnaire, Sleep Hygiene Index and Morningnness-Eveningness Questionnare were used among 202 nurses.

Sleep hygiene is a set of behavioural and environmental practices to assist with insomnia and other sleep-related issues. Includes principles around establishing sleep schedules, using naps tactically, changing the sleep environment around lighting, temperature, humidity, noise etc. and a range of other principles/practices.

Providing background, it’s noted:

·        Shift work is often associated with conflicts between an individuals’ circadian pacemaker and sleep/wake timings that are imposed by shift work schedules; resulting in sleep impairment

·        Individual differences affect tolerance for shift work, influencing the severity of sleep impairment, insomnia etc. This can include older age (which age can also result in a shift to more morning-type diurnal preferences, where morningness is more vulnerable to sleep impairment) and higher body mass index

·        Worsening insomnia has also been linked to higher alcohol and caffeine intake and smoking in shift workers

·        For most shift workers, insomnia and sleepiness are temporary and often recover after return to a normal sleep-wake schedule

·        For some however, shift work can result in chronic impairment, resulting in shift work disorder (SWD)

·        SWD is “a circadian rhythm sleep disorder characterized by the presence of insomnia symptoms and/or sleepiness associated with shift work schedules” (p2)

·        Around 20 – 30% of shift workers may be affected by SWD

Results

Key findings were that:

·        High risk of shift work disorder (SWD) was significantly associated with poorer sleep hygiene scores and greater eveningness preferences compared to the low risk group

·        Indeed, sleep hygiene score was the most significant contributing factor to SWD risk in this study. Every unit increase on the sleep hygiene index score increased the odds of being classified as high risk for SWD by 80%

·        Body mass index, marital status, having children, or caffeine or alcohol intake were significantly associated with SWD

·        Most people at high risk of SWD reported “always” or “frequently” to going to bed at different times, waking at different times, going to bed stressed/angry, or planning/worrying in bed

·        Almost 1/3 of participants in this study were identified as being at high risk of SWD

·        As expected, insomnia and sleepiness correlated well with SWD risk

Some findings below:

Discussing the findings, they note that the high risk of SWD in this sample of shift workers is similar to other data from other industries.

Insomnia and sleepiness were found to have the same significant relationship with performance on the sleep hygiene index and morningness-eveningness questionnaire, supporting the idea that both insomnia and sleepiness should be a focus of treatment for SWD via sleep hygiene.

Sleep hygiene was the most strongly correlated factor for SWD in this sample, supporting the key role that poor sleep hygiene behaviours play in SWD – the higher the score on the sleep hygiene index, the poorer the participant’s sleep hygiene behaviour.

The associations with the sleep hygiene index supports prior work, and supports the role good sleep hygiene practices and awareness/knowledge can play in combatting sleep-related issues.

Diving deeper into sleep hygiene, variability in sleep schedules in the form of going to bed and getting up at different times, or not staying in bed, were significant risk factors in SWD risk; supporting prior work on the role of inconsistent sleep schedules for sleep impairment.

Consistent with sleep hygiene, greater consistency in sleep schedules and prebed routines (screen time etc.), comfort of the bedroom and its lighting and temperature and the like were associated with lower risk of SWD in this sample.

Moreover, minimising stress, worry or anger before bed could be useful tactics to improve sleep, as with finding ways to switch off from work. Prior work shows that high anxiety can lead to insomnia.

Further, they talk about “sleep reactivity, which looks at how sleep is affected by an individual’s ability to cope with stress and shows that individuals who cope better with stress are less likely to have impaired sleep as a result of the stress” (p6).

However, they raise the possibility that poor sleep hygiene could be a compensatory response to sleep problems in some individuals (e.g. the direction of causality between sleep hygiene and sleep problems can be reversed). For instance, an individual “may self-medicate with alcohol or caffeine or watch television because they are having trouble getting to sleep or staying asleep rather than the other way around” (p6).

As expected, several limitations were present.

Authors: Booker, L. A., Barnes, M., Alvaro, P., Collins, A., Chai-Coetzer, C. L., McMahon, M., … & Sletten, T. L. (2020). Sleep, 43(2), zsz228.

Study link: https://doi.org/10.1093/sleep/zsz228

Link to the LinkedIn article: https://www.linkedin.com/pulse/role-sleep-hygiene-risk-shift-work-disorder-nurses-ben-hutchinson