Working Night Shifts Is Associated with Sleep Disorders, Study Finds

Credit: GGZ Drenthe Mental Health Institute

Working night or early morning shifts are associated with ruining the circadian sleep-wake cycle and developing sleep disorders like insomnia, according to new research.¹

Roughly 27% of shift workers with sleep problems develop a shift work disorder, a circadian rhythm sleep-wake disorder containing insomnia symptoms and frequent sleepiness. Many people have shift jobs, and the number keeps rising. In 2010, 17% of European Union workers worked shifts while 21% did in 2015.

Not only are shift workers associated with shift work disorder but they often have comorbid sleep disorders like insomnia, hypersomnia, and sleep-related movement disorder. Sleep issues, such as short sleep and poor quality, poses a risk for other conditions like obesity, cardiovascular diseases, and type 2 diabetes. Long sleep duration also links to infectious and incident cardiovascular diseases and poorer cognitive functioning. Poor sleep can also increase the risk for psychiatric conditions, such as mood disorders, anxiety disorders, and substance-abuse-disorders.

A new cross-sectional study, led by G.J. (Gretha) Boersma, from Forensic Psychiatric Hospital at the GGZ Drenthe Mental Health Institute in Assen, Netherlands, sought to evaluate the presence of short and long sleep—as well as sleep disorders—for people working different shifts (day, early morning, evening, night, and rotating shift).

“The results implicate that regular night shift is by far the most debilitating condition at least concerning sleep; approximately half of the night workers reported short sleep (≤6 hours), 51% scored positive on ≥1 sleep disorder, and 26% on two or more sleep disorders,” the investigators wrote. “An exception was long sleep duration, which was most prevalent in evening shift workers (12%).”

The investigators collected their sample from Belgian readers of the newspaper, De Standaard, who filled out the Holland Sleep Disorders Questionnaire (HSDQ) and provided sociodemographic information. The questionnaire assessed for the following sleep disorders—insomnia, sleep-related breathing disorders, hypersomnia, parasomnia, circadian rhythm sleep-wake disorders, and sleep-movement disorders.

Respondents provided their estimated presence of short sleep duration (≤ 6 hours) as long sleep duration (≥9 hours), as was well their sex, age, education level, living companions, and work schedule. The sample included 50,064 respondents but were only included if they were ≥ 18 years of age and had a shift job. After exclusion, 37,622 participants remained.

In the questionnaire, participants had to report if they were <30 years old, 30 – 50 years old, and >50 years old. They also had to select their education level: elementary school, secondary school at lower level, secondary school at higher level, vocational training, university of applied sciences, and university. The team grouped both secondary school educations together, as well as university of applied sciences with just university.

Participants also had to report if they worked regular day, early morning, evening, night, or rotating shifts. Also, they had to note if they lived alone, with a partner, with children <3 years old, children >3 years old, with parents, and with friends or roommates. In the analysis, they only assessed the categories: alone, with partner, alone with children, with partner and children, and with other(s).

“It is possible that those living alone receive less social pressure to maintain strict circadian patterns of behavior, which may impair their sleep hygiene practices,” the team wrote. “Alternatively, this group may receive less social (familial) support, which has been shown to reduce sleep health.”

The average age of the study was 40.1 ± 12.0 years. Most of the sample were female (59.4%), between the ages 30 – 50 years old (49%), had an academic education (58.7%), had daytime work (86.2%), lived with a partner and child (39.5%), and received on average 6.97 ± 1.02 h per 24 hours.

While sleep disorders were more common in females (insomnia: P < .01; hypersomnia: P < .01; parasomnia: P <.01; circadian rhythm sleep-wake disorders: P < .05; sleep-related movement disorders: P <.05), a significantly larger number of males reported short sleep duration (P <.01) and a smaller number of long sleep duration (P <.01).

Also, as age increased, so did the prevalence of short sleep duration (P < .01) and sleep-related breathing disorders (P <.01). However, long sleep duration (P < .01), insomnia (P < .05), hypersomnia (P <.01), parasomnia (P < .01) circadian rhythm sleep–wake disorders (P <.01), and sleep disorder comorbidities (P < .01) appeared more frequently in the youngest age group.

Meanwhile, having a lower education (elementary or secondary) was linked with a significantly higher prevalence of short and long sleep duration and sleep disorders. The investigators also found living alone, living alone with children and others was associated with a higher prevalence of short sleep and sleep disorders except for parasomnia and sleep-related breathing disorders. Though, just living alone and with others was associated the most with sleep disorders.

People who worked evening shifts had more prevalent long sleep duration. During the day shift, about 12% had insomnia and sleep-related movement disorders. Circadian rhythm sleep-wake disorders slightly increased for people who worked morning shifts, but sleep disorders and sleep disorder comorbidities were the most prevalent in the night shift workers. Over half (51.1%) of the night shift group reported having ≥1 sleep disorder, and 26.3% reported ≥ 2 sleep disorders.

The investigators point how the “night shift is associated with the largest change in sleep-wake timing” and how the circadian system struggles switching from a day to night schedule. Yet, about 25% of people work night shifts despite our “day-oriented society.”

“Because those working night shift will remain de-synchronized with the day-work focused environment they live in, it is unlikely to completely prevent all negative consequences of night work,” said Dr. Marike Lancel, another investigator of the study.²

^References

1. ^{Boersma, G, Mijnster, T, Vantyghem, P. Shift Work Is Associated with Extensively Disordered Sleep, Especially When Working Nights. Frontiers in Psychiatry. December 7, 2023. https://doi.org/10.3389/fpsyt.2023.1233640. Accessed December 11, 2023.}
2. ^{Working Night Shifts Causes Sleep Disorders in More Than Half Of Workers. EurekAlert! December 7, 2023. https://www.eurekalert.org/news-releases/1009689. Accessed December 11, 2023.}