The researchers asked 5,881 individuals born in 1966 in northern Finland about their professional 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. Study participants were monitored for a period of four years.
Ten percent of men and 12% of women were “of the evening type,” 72% of whom worked in day jobs, the researchers found. The rest of the people were evenly divided into early risers, or what the researchers called intermediate chronotypes.
A quarter of people classified as nighttime rated their own work performance as poor, using what the researchers described as an internationally accepted scale designed to identify individuals with low work ability and a higher risk of retiring early because of disability. This was a significantly higher proportion than among the first or intermediate chronotypes, the research said.
The chances of low performance were twice as high among night owls than among early risers of both sexes, even after taking into account potentially influential factors, such as sleep duration and morning hours of work, the study revealed, published Tuesday. fair in the newspaper Occupational and Environmental Medicine.
“If nighttime types have to work early in the morning, they will not rate their ability to work as high as those in the morning. The reverse would also be true. If normal business hours were from 3 pm to 11 pm, morning types would sit if worse than nocturnal types, “said Kristen Knutson, associate professor at Northwestern University, who researches the association between sleep, circadian rhythms and cardiometabolic diseases, including diabetes, obesity and cardiovascular disease.
“The underlying mechanism is our internal biological clock that determines the time of day when we perform best,” said Knutson, who was not involved in the research.
Although the population studied is from an area of Finland, Knutson said the findings “probably 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 am, and manual work even earlier – so their findings may not be applicable everywhere, and the topic should be studied further. background.
“This was the first population-level study to provide evidence that the night chronotype may be related to low work capacity,” said study authors, Dr. Tapio Räihä and Leena Ala-Mursula, professor of occupational health, at 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 very much in line with previous evidence that evening is related to health and functioning problems.” they added, using their word for the night chronotypes.
Suzanne Hood, associate professor at Bishop’s University in Quebec, Canada, said night owls should not be alarmed by the findings.
Assessing job performance doesn’t necessarily say about the quality of work in real terms, noted Hood, who studies the body’s circadian rhythms. In addition, the study was observational – that doesn’t mean that being a night owl makes you less able to work. In addition, employers can benefit from people with different chronotypes.
“For example, the employee who appears to have a slow start in the morning may be the person best able to work effectively at 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, she said there was a lot of evidence to show “that the chronotype can affect your cognitive sharpness, which can affect performance at work or in the classroom”.
“This influence is clear when you challenge someone to pay attention and remember information at a time of day that is out of your preference: for example, asking a night person to give an important presentation to customers at a breakfast meeting at 7.30 am Some people may have experienced this kind of mental cloudiness during jet lag. “
Hood said there are several mechanisms that may be at work, 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 person at night who arrives at the office at 8 am may have slept only 6 hours, while the person in the morning who arrives at the same time has 8 hours,” he explained.
“I encourage people whose work hours are out of sync with their chronotype to try to follow a regular sleep schedule to avoid sleep deprivation,” said Hood. “Chronotypes are a bit malleable, so we can change our favorite times of the day a little bit, maintaining a daily sleep and wake up routine.”