The Dull Numbing of Shift Work

By Richard Asa  @RickAsa
March 02, 2015

It may be like long-lasting jet lag, but you can fight back.

We’re all familiar with the cautionary modern proverb of “working yourself to death.” In Japan, they have a word for it, karoshi, which means “death from overwork,” or occupational sudden death.

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

Your brain may actually change from repetitive shift work, according to researchers measuring the speed of response and level of memory in more than 3,000 employed and retired workers, about half of whom worked shifts, many for more than 10 years.

In a study published in the journal Occupational & Environmental Medicine, researchers said shift work was associated with cognitive impairment, when people have trouble remembering, learning new things, concentrating, or making decisions about their daily life. The more years someone worked a shift, the worse their brain performed.

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

Shift work, which the researchers compared to chronic jet lag, disrupts your circadian rhythms – the body’s natural sleep clock – and social life. 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.

“This study shows that being involved in shift work currently or in the past can result in poor cognitive performance,” says Zianka Fallil, MD, a neurologist at the North Shore-Long Island Jewish Health System. “Cognitive decline from being involved in shift work is equivalent to a 4.3 year age-related decline.”

In addition, she adds, the study shows that workers who have been exposed to shift work for more than 10 years “have markedly lower global cognitive performance as compared to people who have never been involved in shift work. This effect was equivalent to a 6.5 year age-related cognitive decline.”

Shift work has been associated with metabolic syndrome, a combination of factors that increase your risk for heart disease, diabetes, and stroke. Shift workers may also be more prone to vitamin D deficiency because they 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 shfit 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 over-schedule 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.


February 24, 2020

Reviewed By:  

Christopher Nystuen, MD, MBA