Shift Work Could Harm Cognitive Function

Those who work in shifts took longer on cognitive tests, Uppsala University study says.


Work outside the traditional nine to five could interfere with cognitive function, a new study says.

Researchers at Uppsala University in Uppsala, Sweden, found that those who work in shifts--like retail clerks, police officers and parking lot attendants--take longer on cognitive tests than those who work traditional jobs or those who have not done shift work in five years.

In this study examining cognitive tests of 7,000 people aged 45 to 75, researchers set out to predict whether shift work influenced tests scores. The cognitive tests included one called the "Trail Making Test," which entails connecting circles with numbers inside them in ascending order and connecting letters and circles in ascending order at the same time.

"Our results indicate that shift work is linked to poorer performance on a test that is frequently used to screen for cognitive impairment in humans," Christian Benedict, an associate professor at the Department of Neuroscience at Uppsala University and co-author of the study, said in a press release.

Several recent studies have linked shift work to poor health outcomes including mental health disorders, a higher chance of birth defects or miscarriage, cardiovascular issues, increased likelihood of cancer, fatigue and sleep disorders.

The sleep disruptions associated with shift work also lead the International Classification of Sleep Disorders to classify a "shift work disorder." Symptoms of the disorder include insomnia, drowsiness, depression and problems in relationships.

However, this recent study did find some good news: those who had not worked in shifts for five years did just fine on the tests.

"The poorer performance was only observed in current shift workers and those who worked shifts during the past five years. In contrast, no difference was observed between non-shift workers and those who had quit shift work more than five years ago," Benedict said in the release. "The latter could suggest that it may take at least five years for previous shift workers to recover brain functions that are relevant to the performance on this test."

As for what a shift worker can do to minimize the health consequences of his or her job, the University of California Los Angeles Sleep Disorders Center recommends napping, eating healthy foods, facilitating understanding from friends and family and sleeping at the same time every day.

This study was published May 14 in the journal Neurobiology of Aging.

The Swedish Research Council, Swedish Brain Foundation, AFA Insurance and the Novo Nordisk Foundation funded this study.

Researchers declared no conflicts of interest.