Shift workers, such as doctors, flight attendants, bartenders and police officers, have been found to be at a greater risk of certain chronic diseases.
Shift work has its own demands that set it apart from jobs with traditional working hours. Shift work has its benefits; it can be more convenient from a child care perspective, is sometimes better paid and can allow workers time for other activities, such as study.
However, the medical and scientific communities are continually reporting that shift work can increase the risk of certain disorders and have a negative impact on the overall well-being of employees.
In this article, we take a look at what has been reported recently about the effects of shift work, what reasons could possibly be behind these findings and what people working shifts can potentially do to lower their risks of various health problems.
Shift work in the US
Shift work tends to be classified as any work schedule that involves hours that are irregular or unusual in comparison with the traditional daytime work schedule that usually occurs between 6 am and 6 pm.
The term shift work can, for this reason, refer to working evenings, overnight, rotating shifts or irregular employer-arranged shift patterns.
According to an article published in 2000 by the Bureau of Labor Statistics (BLS), over 15 million (16.8 %) full-time wage and salary workers are employed working alternative shifts. Of these, the most common alternative shifts are evening shifts, with working hours usually between 2 pm and midnight, and irregular shifts with a constantly changing schedule.
In contrast, the University of California-Los Angeles (UCLA) Sleep Disorders Center reports more than 22 million Americans work evening, rotating or on-call shifts.
Recently, the BLS reported that the proportion of full-time wage and salary workers employed working alternative shifts now sits at 14.8%. This figure is supported by a poll conducted by the National Sleep Foundation (NSF) in 2005, which found 14% of Americans work shifts.
While there has been a slight drop in the number of white Americans working these hours - from 16.2% in 1997 to 13.7% in 2004 - the proportion of black, Asian and Latino Americans working alternative shifts has remained largely the same. In May 2004, the percentages for these groups were 20.8%, 15.7% and 16%, respectively.
Shift work is most commonly found within industries that provide services around the clock, such as food services, transportation, health services and protective services like the police force.
At first glance, it appears as though the main factor connecting shift workers is that they work different hours to the typical "9-to-5" routine. However, multiple studies report that there is something else that connects bar staff, long-distance truck drivers, nurses and police officers - an increased risk for certain diseases.
Previous studies reported by MNT
Medical News Today have reported on various studies associating shift work with an increased risk of certain health problems. These associations have ranged from the somewhat predictable to the surprising.
In July 2014, a meta-analysis published in Occupational and Environmental Medicine suggested that shift workers face an increased risk of type 2 diabetes. In particular, people working rotating shifts face an increased risk of 42%.
A 2014 study suggested shift work may raise the risk of type 2 diabetes.
The authors theorized that rotating shifts made it more difficult for workers to maintain a regular sleep-wake cycle, negatively affecting sleep quality and potentially weakening insulin resistance.
Then, in November 2014, another study published in the same journal suggested that shift work could impair the functioning of the brain.
Study participants who were currently working or had previously worked shifts scored lower in tests assessing memory, processing speed and overall brain power than participants working traditional daytime hours.
"The cognitive impairment observed in the present study may have important safety consequences not only for the individuals concerned, but also for society as a whole," wrote the study authors, "given the increasing number of jobs in high hazard situations that are performed at night."
More recently, a study published in the American Journal of Preventive Medicine reported that female nurses working rotating night shifts for 5 or more years could be at an increased risk of all-cause and cardiovascular disease mortality.
In addition, working rotating night shifts for 15 years or more was found to potentially raise the risk of lung cancer mortality.
A quick perusal of these studies indicates another factor that shift workers are likely to have in common - disruptions to the sleep-wake cycle. Shift work can lead to workers sleeping at strange or varying times of day, potentially resulting in reduced amounts of sleep.
But how much of an impact can sleep disruption have on an individual's health?
On the next page, we look at what circadian rhythms are and what can be done to protect the health of shift workers.