It’s well-established that working nights or rotating shifts can impact workers’ health and sleep patterns, and make them must vulnerable to injuries on the job. (For example, shift work and diet have been linked to inflammation and health issues and night and shift workers are most likely to get injured.) Such work hours can also result in the development of shift work disorder, a combination of difficulty sleeping and excessive sleepiness while awake.
But a recent study out of Norway found that the number of hours between shifts can be just as important as which hours are actually worked.
The new study by researchers at the University of Bergen found that nurses who often return to work with less than 11 hours between shifts are at higher risk of sleep problems and severe fatigue than others.
In 2009 and 2010, the researchers sent questionnaires to several thousand randomly selected nurses in Norway—1,224 filled out and returned the surveys for both years. Almost all of the nurses were female and had an average age around 34.
The surveys asked how often over the past year the nurses had “quick returns”—that is, worked two shifts with less than 11 hours in between, usually an evening shift followed by a morning shift with a break of only nine to 10 hours. They also included questions about:
- Mental and physical fatigue
- Anxiety and depression
- Hypothetical situations in which the nurses might doze off.
Results: The nurses reported having an average of 33 instances of quick returns between shifts over the previous year. Nurses who reported more quick returns in 2009 were slightly more likely than others to have shift work disorder or pathological fatigue.
But those who reduced their number of quick returns between 2009 and 2010 also reduced their risk of pathological fatigue by about 30%.
Bottom line: Short breaks between shifts may create a work-related health risk. So when scheduling workers, try to ensure that workers get enough hours between shifts to adequately rest.
For example, so-called “hours of service” regulations, which apply to commercial drivers such as truckers and bus drivers, recognize the need for sufficient breaks between shifts and so generally require such drivers to get at least eight consecutive hours off duty between on duty shifts.