The researchers asked 5,881 people born in 1966 in northern Finland about their working life and health and asked them about their sleep patterns to determine what their natural chronotype was in 2012 when they were 46 years old. The study participants were monitored for a period of four years.
Ten percent of the men and 12% of the women were “night guys,” 72% of whom worked day jobs, the researchers found. The rest of the people were largely evenly divided into early risers, or what the researchers called intermediate chronotypes.
A quarter of people classified as nocturnal rated their own work performance as poor using what the researchers described as an internationally accepted scale developed to identify people with low work capacity and an increased risk of early retirement due to disability . This was a significantly higher proportion than among the first or intermediate chronotypes, according to the research.
The odds of poor performance were twice as high among night owls than early risers in both genders, even after accounting for potentially influential factors such as sleep duration and morning work hours, the study found, which was published Tuesday in the magazine. Occupational and environmental medicine.
“If night guys have to work early in the morning, they won’t rate their work capacity as high as morning guys. The reverse would also be true. If normal business hours were from 3:00 pm to 11:00 pm, They feel worse at dawn than at night, “said Kristen Knutson, an associate professor at Northwestern University who investigates the association between sleep, circadian rhythms, and cardiometabolic diseases, such as diabetes, obesity and cardiovascular disease.
“The underlying mechanism is our internal biological clock that dictates the time of day we perform best,” said Knutson, who was not involved in the research.
While the population studied was from one area of Finland, Knutson said the findings “probably apply” to the United States since biological clocks are universal. However, the researchers noted that office work in Finland starts early, usually at 8 a.m., and manual work even earlier, so their findings might not be applicable everywhere, and the topic should be studied further. .
“This was the first population-level study to provide evidence that the evening chronotype might be related to poor work capacity,” said study authors Dr Tapio Räihä and Leena Ala-Mursula, professor of care at occupational health, 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 evening sleep is related to poorer health and function.” they added, using their word for evening chronotypes.
Suzanne Hood, an associate professor at Bishop’s University in Quebec, Canada, said night owls shouldn’t be alarmed by the findings.
Rating job performance doesn’t necessarily tell you about job quality in real terms, said Hood, who studies the body’s circadian rhythms. Also, the study was observational, it doesn’t mean that being a night owl makes you less able to work. Also, employers could benefit from people with different chronotypes.
“For example, the employee who looks like a slow beginner in the morning might be the person who is best able to work effectively into the night to meet an important deadline,” said Hood, who was not involved in the research.
“If there is any opportunity for flexibility in scheduling, allowing employees some control over the time of day they complete their work can help optimize performance and productivity.”
However, he said there was a lot of evidence to show “that chronotype can affect your cognitive acuity, which can influence performance at work or in the classroom.”
“This influence is clear when you challenge someone to pay attention and recall information at a time of day that is not their preference: for example, asking an afternoon person to give an important presentation to clients at a business meeting. breakfast at 7:30 am Some people may have experienced this kind of mental confusion in the middle of jet lag. “
Hood said there were several mechanisms that could be at play, including lack of sleep and how your body’s daily rhythms affect how it responds to information and different environments.
“Due to differences in disposition to fall asleep, the evening person arriving at the office at 8 am may have only slept 6 hours, while the morning person arriving at the same time had 8 hours “he explained.
“I would encourage people whose work schedule is out of sync with their chronotype to try to stick to a regular sleep schedule to avoid being deprived of sleep,” Hood said. “The chronotypes are a bit malleable, so we can change our preferred hours of the day a bit by maintaining a daily routine of hours of sleep and wakefulness.”