The Dull Numbing of Shift Work

Shift work can increase your risk of having trouble remembering, learning new things, concentrating, or making decisions about your daily life.

We’re all familiar with the cautionary modern proverb about “working yourself to death.” The Japanese call death from working too much karoshi.

This is no theoretical concept. Cases of karoshi have been reported in Japan since 1969. In the bubble economy of the 1980s, when more workers died, the phenomenon was formally labeled. During the collapse of the bubble economy and subsequent recession — which resulted in mass layoffs — remaining workers put in excessive time and more died.

The Japanese recognized that you really can die from working too much. What happens if you work, day after day, when your brain thinks you should be asleep?

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Shift work — defined as being on duty during hours outside the standard business day — disrupts workers’ normal circadian rhythms, the body’s natural clocks. It disrupts social life and increases the risk of many illnesses.

It also accelerates cognitive decline, according to an international team of researchers, who gave memory tests to more than 3,000 employed and retired workers, about half of whom worked shifts, many for more than 10 years.

The team concluded that shift work increased the risk of having problems remembering, learning new things, concentrating, or making decisions about daily life. The more years people worked odd hours, the worse their performance.

The decline was the equivalent, on average, of more than 4 years of aging. For those who worked shifts for more than 10 years, the decline jumped to the equivalent of 6.5 years of aging.

Other studies had already established that shift work hours have a negative effect on workers’ alertness and cognitive efficiency, during work hours and the days after working. Studies have also examined whether these effects are lasting.

The disruption may throw your system into physiological stress, causing the release of chemicals that “have an impact on brain structures involved in cognition and mental health over the lifespan,” the researchers said.

Shift work has been associated with metabolic syndrome, a combination of factors that increase your risk for heart disease, diabetes, and stroke.  Ulcers, breast cancer, and reproductive difficulties are also more common among shift workers. There is a possible link to higher rates of prostate cancer.

It may be that the cognitive decline is caused by shortages of vitamin D, the sunshine vitamin. If you’re sleeping during daylight hours, you may spend less time in the sun. “Vitamin D deficiency has also been linked to impaired cognitive function,” the researchers said.

The damage is probably not permanent. The researchers believe the changes are reversible over time because they are similar to the dull numbing our brains experience after repeated jet lag. Jet-lagged workers recover their wits with time; studies have shown they regenerate tissue in the hippocampus, the part of the brain important for memory and emotion.

It may take at least five years, however, to reverse the effects of shift work, if you work the night shift 10 years or longer, the researchers suggested.

The study may be a useful warning, “given the increasing number of jobs in high-hazard situations that are performed at night,” the researchers said. In other words, your job can, and may be, affecting your quality of life. In the end, that’s really all there is.

Stuck with shift work? Try these sleep tips:

• Maintain the same schedule of sleeping and waking during your days off and your work days. Eat on a consistent schedule.
• As with jet lag, it is easier to add hours of rest than subtract them: For jet lag, it's easier to fly west than east; for shift work, it's easier to start your next week of shift work later rather than earlier.
• Upon awakening, if the sun is still out, head outdoors, take a walk, and try to get some sunshine to reset your biological clock. If there's no sun, inexpensive commercially available full-spectrum light boxes can help.
• If you feel tired before a night shift, consider a short nap prior to work, or, if possible, a quick nap during lunchtime.
• Take time for yourself. Don’t overschedule or overextend yourself to accommodate the schedule of friends and family who have normal day schedules. You need your sleep, too.
• If you are changing from a night shift to a normal day schedule, a short sleep after your last night shift of the week may help you get some daylight and return to a normal daytime schedule. Also, go to bed early that night to catch up on sleep.
• Exercise before a shift if you have the time and energy. You can expose your body to some daylight and work off some stress.
• Establish a regular bedtime routine and maintain it.
• Make your environment conducive to sleep, such as keeping it cool, dark, and quiet.
• Avoid caffeine late in your shift, or alcohol before bedtime; having either within 3 to 4 hours of bedtime will decrease your sleep quality. 
• Avoid bright lights or sunshine before bedtime. Dark sunglasses may be helpful during your commute home. Use public transportation if possible; shift workers have a higher risk of auto accidents when dealing with variable work-sleep schedules.
• Tell people your work hours so you will be left alone when do have time to sleep.

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