Shift Work and Sleep Disturbance in the Oil Industry

This studied sleep duration, sleep quality and a range of other sleep factors related to rotating shift workers in the US oil industry (n = 351).

All data was via survey (including sleep logs), so note that limitation.

Providing background, it’s noted:

·????????Since the 90s, most refineries in the US have been staffed via two 12-hr shifts – changing from day to night every 2-4 days

·????????Prior to this change, 8-hr shifts were common and with a slower rotation frequency

·????????While some work highlights rapid rotations as being less disruptive to sleep, other data found rapid rotation as more disruptive to sleep quality and quantity

·????????Actual work schedules/actual hours have been shown to differ substantially from nominal schedules, with frequent overtime interrupting recovery

·????????Long work hours are associated with short sleep duration. In healthcare, higher prevalence of shift work disorder, shorter sleep duration, higher fatigue, decreased performance and heightened errors have been associated with 12-hr shifts compared to 8-hr, whereas for industrial workers some conflicting evidence exists

·????????For accidents, a review of four studies found elevated accident risk after the ninth hour of shift

·????????Shift work disorder is associated with gastrointestinal disorders, depression, anxiety and fatigue

·????????Circadian misalignment may also result from shift work, since shift work “conflict with social and biological circadian rhythms” (p1)

·????????Older workers tend to have shorter and more disrupted sleep. Moreover, circadian phase and chronotype may also advance with age. Age may also slow adjustment to circadian rhythm disruption from rotations, reduce sleep after night shifts and increase insomnia

Results

Overall, survey data of US oil workers indicated:

·????????Impaired sleep quality and short sleep durations were common and were associated with health and mental health outcomes among shift workers

·????????Shortest sleep durations followed shift rotations

·????????Early rise and start times were associated with shorter sleep duration and poorer sleep quality

·????????Drowsiness and fatigue-related incidents were reported commonly

·????????Lower sleep duration and quality and increased overtime in 12-hr rotating shift schedules

·????????Long workdays with early start times may reduce available hours for quality sleep

For more specific findings, it was found that:

·????????78.2% of participants reached the threshold for a sleep disorder, whereas 34.8% reached the threshold for severe sleep disorders

·????????Self-rated sleep quality was rated as very bad in 9.6%, fairly bad in 45%, fairly good in 41.5% and very good in 4%

·????????Sleep quality improved with age and years of experience in refining, but wasn’t associated with age at career start [** the former may be linked to the survivor population effect, where people ill-suited to these workstyles leave the industry, leaving a targeted sample of people who are better suited]

·????????A linear association was found between decreased sleep quality scores and increased anxiety, depression and job stress, in conjunction to increased gastrointestinal symptoms

·????????Certain lifestyle characteristics were associated with sleep scores. Good sleepers tended to have greater exercise frequency and leisure activities, shorter work commute lengths, greater years of work history, greater staffing availability, ease of taking time off work, lower job stress, lower gastrointestinal symptoms and less anxiety and depression

·????????In contrast, poorer sleepers performed statistically worse on the above characteristics

·????????Alcohol, age, caffeine and smoking weren’t significant predictors

·????????A slight majority (50.6%) reported short sleep durations (less than 6 hours per night)

·????????Age and years of work experience were significant predictors with sleep duration

·????????Commuting time and overtime were significant predictors of sleep duration, whereas shift length had a weak association.

For shift variables, a shift-dependent variation in sleep duration was found in the 12-hr shifts. Those with history of rotating shift schedules had shorter sleep duration and poorer sleep quality than those who worked permanent days.

Sleep quality improved for those on leave. Sleep duration was longer during 8-hr shift sets compared to 12-hr sets. Shortest sleep durations were reported following rotation, then during night shift, then day shift, then time off.

Total weekly sleep time was inversely related with total hours worked.

As expected, people slept longer on their days off – an extra 28 mins sleep for each hour later participants woke on day shifts. Sleep increased 19 minutes for each hour later their shift started.

For night shifts, hours slept increased 15 mins with later rise times, but not later shift start times.

Later rise and start times were significantly correlated with improved sleep quality.

For incidents, a third of the population reported at least one fatigue/sleep related incident. A fourth reported a near miss at work, 7.6% reported a vehicle accident while commuting [** noting that recall of incidents and their causal factors is likely to be one of the most variable and inaccurate types of data in this survey].

Based on reported incidents, every one unit increased in the sleep survey score increased the odds of a safety event: for near misses the odds ratio was 1.11, vehicle accident at 1.14, serious error 1.12 and a reportable accident at 1.09.

Discussing the findings, the authors note that sleep duration and sleep quality were severely impacted in this sample of US oil refinery workers.

Although it’s difficult to avoid rotating & extended shift schedules, a number of modifications can be made to potentially improve sleep-related factors. For instance, early rise and start times severely impact sleep.

One study found that early rise times (to commence an early shift) aren’t accompanied with an earlier bedtime; resulting in a sleep debt.

Link in comments.

Authors: McNamara, K. A., & Robbins, W. A. (2023). Workplace Health & Safety, 21650799221139990.