The researchers asked 5,881 individuals born in 1966 in Northern Finland about their working life and health and asked them about their sleep patterns to determine their natural chronotype in 2012, when they were 46 years old. The study participants were followed for a period of four years.
Ten percent of the men and 12% of the women were “ evening types, ” 72% of whom worked in day jobs, the researchers found. The rest of the humans largely distributed evenly into early risers, or what the researchers called intermediate chronotypes.
A quarter of people classified as evening types rate their own performance at work as poor based on what the researchers describe as an internationally accepted scale designed to identify individuals with poor work ability and higher risk of getting premature. to retire because of a disability. This was a significantly higher rate than in early risers or intermediate chronotypes, the study said.
The likelihood of underperformance was twice as high in the night owls as in the early risers in both sexes, even when taking into account potentially influential factors such as sleep duration and morning work hours, the study, published Tuesday in the journal . Occupational and Environmental Medicine.
“If evening types have to work in the early morning, they will not rate their work ability as high as the morning types. The reverse would also be true. If normal business hours were 3:00 pm to 11:00 pm, the early ones would feel worse than evening types.” , says Kristen Knutson, associate professor at Northwestern University who studies the link between sleep, circadian rhythms and cardiometabolic diseases, including diabetes, obesity and cardiovascular disease.
“The underlying mechanism is our internal biological clock that determines when we perform best,” said Knutson, who was not involved in the study.
Although the population studied was from part of Finland, Knutson said the findings “likely apply” to the United States, since biological clocks are universal. However, the researchers pointed out that office work in Finland starts early – usually at 8 a.m., and manual work even earlier – so their findings may not be applicable everywhere and the topic needs to be studied further.
“This was the first population-level study to provide evidence that evening chronotype may be associated with poor work ability,” said the study’s authors, Dr. Tapio Räihä and Leena Ala-Mursula, professor of occupational health care, from the Center for Life Course. Health research at the University of Oulu, Finland, in an email.
“We recognize that these observational findings are new and need to be confirmed in other studies. Still, our results are in line with previous evidence that eveningness is linked to poorer health and functioning,” they added, using their word for evening chronotypes.
Suzanne Hood, associate professor at Bishop’s University in Quebec, Canada, said night owls should not be alarmed by the findings.
Assessing work performance doesn’t necessarily tell you about the quality of the work in real terms, noted Hood, who studies the body’s circadian rhythms. The study was also observational – it doesn’t mean you can’t work any less well as a night owl. In addition, employers can take advantage of people with different chronotypes.
“For example, the employee who appears to be a slow starter in the morning may be the person who is best able to work effectively into the evening to meet an important deadline,” said Hood, who was not involved in the study.
“If there is some scope for flexibility in scheduling, it can help optimize performance and productivity by giving employees some control over when they complete their work.”
However, she said there was a lot of evidence to show “that chronotype can affect your cognitive acuity, which can contribute to performance at work or in the classroom.”
“This influence is evident when you challenge someone to pay attention and remember information at a time that is beyond their preference: for example, by asking an evening person to give an important presentation to customers at a 7:30 am breakfast meeting Some people may have experienced this kind of mental foggy during jet lag. “
Hood said there are several mechanisms that can play a role, including sleep deprivation and how your body’s daily rhythm affects how you respond to information and different environments.
“Due to the differences in sleep readiness, the evening person who arrives at the office at 8 in the morning may have only slept for 6 hours, while the morning person who arrives at the same time had 8 hours,” she explains.
“I would encourage people whose work schedules are not in sync with their chronotype to try and maintain a regular sleep schedule to avoid sleep deprivation,” Hood said. “Chronotypes are a little malleable, so we can shift our favorite times of the day a bit by keeping a daily routine of sleep and wake times.”