The researchers asked 5,881
Ten percent of men and 12% of women were “evening types,” 72 percent of whom worked day jobs, the researchers found. The rest of the people divided themselves fairly evenly in early travels, or what the researchers called intermediate chronotypes.
A quarter of people classified as evening types rated their own performance at work as poor using what researchers described as an internationally accepted scale, developed to identify people with poor work ability and a higher risk of retiring early due to disability. This was a significantly higher proportion than among early birds or intermediate chronotypes, the research said.
Odds of underperformance were twice as high among night owls as they were among the early birds of both sexes, even after taking into account potentially influential factors such as sleep duration and morning working hours, the study, published Tuesday in the journal, found. Occupational and environmental medicine.
“If evening types have to work early in the morning, they will not rate their work ability as highly as morning types. The reverse would also be the case. If the normal opening hours were 3pm to 11pm, the early morning types would feel worse than evening types,” says Kristen Knutson, associate professor at Northwestern University, who researches the link between sleep, circadian rhythm and cardiometabolic diseases, including diabetes, obesity and cardiovascular disease.
“The underlying mechanism is our internal biological clock, which dictates the time of day we do best,” said Knutson, who was not involved in the research.
While the population studied was from an area in Finland, Knutson said the results “probably apply” to the United States, as biological clocks are universal. However, the researchers pointed out that office work in Finland starts early – typically at 8 and manual work even earlier – so their results may not apply everywhere and the topic should be investigated further.
“This was the first study at the population level to prove that evening chronotype could be related to poor work ability,” said study authors Dr. Tapio Räihä and Leena Ala-Mursula, Professor of Occupational Health, from the Center for Life Course Health Research at the University of Oulu, Finland, in an email.
“We recognize that these observational results are new and need to be confirmed in other studies. Nevertheless, our results are in good agreement with previous evidence that the evening is related to poorer health and function,” they added by using their words for evening chronotypes.
Suzanne Hood, an associate professor at Bishop’s University in Quebec, Canada, said night owls should not be alarmed by the results.
Judging job performance does not necessarily tell you about the quality of work in real terms, noted Hood, who studies the body’s circadian rhythm. The study was also observational – that does not mean that being a night owl makes you less able to work. Plus, employers could benefit from people with different chronotypes.
“For example, the employee who acts as a slow start in the morning may be the person most able to work efficiently in the evening to meet an important deadline,” said Hood, who was not involved in the research.
“If there is some flexibility in planning, it can give employees some control over what time of day they complete their work, helping to optimize performance and productivity.”
However, she said there was plenty of evidence that “chronotype can affect your cognitive acuity, which can play into performance at work or in the classroom.”
“This influence is evident when you challenge someone to pay attention and remember information at a time of day outside their preference: for example, asking an evening person to deliver an important presentation to clients at a breakfast meeting at 7 a.m. Some people may have experienced this kind of mental fog during jet lag. “
Hood said there were several mechanisms that could be at play, including sleep deprivation and how your body’s daily rhythms affect how you respond to information and different environments.
“Due to differences in readiness to fall asleep, the evening person who arrived at the office at 8, having only had 6 hours of sleep, while the morning who arrived at the same time had 8 hours, ”she explained.
“I would encourage people whose work schedule is not in sync with their chronotype to try to follow a regular sleep schedule to avoid being deprived of sleep,” Hood said. “Kronotypes are a bit agile, so we can change our favorite times of the day a bit by keeping a daily routine of sleeping and waking up.”