Shift Work May Actually Hurt Your Ability To Think

When the Labor Department announced earlier this week it will extend overtime protections to millions of additional workers starting Dec. 1, advocates applauded. But a growing group of researchers is calling attention to a separate concern that affects many workers in the same group: In addition to how long employees work, worker health depends on when those hours are worked.

A new study links shift work to poorer cognitive functioning, finding that workers who reported having irregular shift schedules performed poorly on a test that measures cognitive decline, compared to those who had never or not recently performed shift work. 

The test used in the study forces the brain to process conflicting information, said study co-author Christian Benedict, an associate professor in the Department of Neuroscience at Uppsala University, noting that processing conflicting information “appears highly relevant in stressful job-related situations.”

The bottom line is not good for shift workers. This research joins a host of other studies that document the ways working irregular shifts harms health, including raising the risk of diabetes, obesity, some cancers, workplace injury and heart disease. Some findings show that women may be even more vulnerable to these effects. 

Considering a large proportion of today’s workforce performs shift work — approximately 15 million Americans, according to data from the Bureau of Labor Statistics — the findings are troublesome, Benedict said.

Shift workers performed worse on executive functioning tests

The study, published earlier this week in the journal Neurobiology of Aging, included 7,143 workers. According to their self-reported work histories, 4,611 had never performed shift work, 1,531 performed shift work more than five years prior, 358 performed shift work within the past five years and 643 were currently working shifts. Everyone in the study completed the trail-making test, a challenge neurologists frequently use to measure cognitive processing speed and executive function in order to assess cognitive impairment. Performance on the test is measured by how long it takes a person to connect a series of numbers in ascending order.

Current and recent (within five years) shift workers took four seconds longer on average to complete the more demanding portion of the test that measured executive function — approximately 60 versus 56 seconds, compared with those who had never performed shift work and those who hadn’t done it for five years or more. Those results account for any other factors that might influence how someone performed on the test, like age, gender, educational status, physical activity level, perceived stress, sleep duration and cumulative sleep disturbance score.

The researchers did not specifically measure brain activity in one region versus another for this study, but Benedict explained the findings are interesting because previous research has shown the executive function portion of the test involves the frontal lobe of the brain, and that type of brain activity is the type that is known to decrease with age.

Disturbed circadian rhythm to blame

The problems with shift work stem from circadian misalignment — i.e. sleeping, working, eating and being awake at the wrong times according to your body clock. Such misalignment can wreak havoc on health over time, sleep expert Charmane Eastman, a professor in the behavioral sciences department at Rush University Medical Center in Chicago, previously told The Huffington Post.

Studies in shift workers have shown that this internal body shifting may affect metabolism in ways that subsequently increase the risk of cardiovascular disease, as well as change levels of various hormones involved in brain function, which some research suggests might explain why memory problems and cognitive decline are associated with shift work.