A group of construction workers working during the night at a construction site.

Work Odd Hours and Your Memory Might Go to Shift

Not everyone is able to work a regular 9-to-5, but a new study shows how night shifts and rotating shift work can lead to cognitive impairment.


Over one million Canadian employees regularly work night shifts, with many others working some form of rotating shift work: a work schedule that takes place outside of the traditional 9-to-5. Previous research has uncovered the negative impacts that shift work can have on our physical and mental health.

Now, new research from York University has found that shift work can lead to cognitive impairment and memory issues as well. Durdana Khan, a recent PhD graduate in Kinesiology and Health Science at York University, was corresponding author of the study published in PLOS ONE.

Although fields ranging from nursing to astronomy often require shift work, these irregular schedules can have detrimental effects on our health. Scientists have long known that shift work can lead to fatigue and burnout, as well as increase the risk of digestive issues and other physical health problems.

In their study, Khan and colleagues analyzed data from nearly 50,000 Canadian adults aged 45 to 85 years who had participated in the Canadian Longitudinal Study on Aging. The participants were asked about their work schedules and employment history, and also reported their results from four cognitive function tests.

The researchers found that shift work is relatively common among Canadian adults: in total, 21% of study participants had been employed in some form of shift work at some point in their lives. Worryingly, employees who worked night shifts tended to have higher rates of cognitive impairment compared to those who only worked during the day. Night shifts were also associated with memory issues, while employees who worked rotating shifts tended to exhibit executive function impairments.

These negative effects may come from the disruption to our natural circadian rhythms caused by shift work schedules, the authors go on to explain. The body’s circadian rhythm controls a number of important processes, such as alertness, appetite, and body temperature. Disruptions to this rhythm caused by sleeping during the day (or regularly changing the body’s sleep schedule, as is the case for rotating shift workers) can throw these processes out of balance and lead to negative health outcomes.

The authors hope that employers will take these results into account and find solutions for employees that will help decrease their risks of cognitive impairment.

For example, recent studies have highlighted the utility of bright light interventions for reducing fatigue amongst night shift workers. Similar interventions — as well as reductions in shift work schedules for aging adults — may help keep Canadian shift workers healthy.

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Emily Deibert is a PhD student in the Department of Astronomy & Astrophysics at the University of Toronto with a passion for science outreach and communication. She earned her HBSc (Astronomy, English, and Mathematics) at the University of Toronto. She is excited about turning scientific research into stories and sharing these stories with the public.