Previous research has shown that so-called “night owls”, who stay up later and struggle to drag themselves out of bed in the morning, are more likely to suffer from a range of health problems.
In 2018, a large study in the United Kingdom found that evening people had a 10% higher risk of dying than morning folks over a 6.5-year period.
While that was potentially worrying news for the world’s night owls, that research did not take into account factors, such as alcohol consumption, that could be behind those deaths.
So researchers in Finland sought to find out more in a study published in the peer-reviewed journal “Chronobiology International”, following close to 24,000 same-sex twins in Finland, who were asked in 1981 to identify whether they were a morning or evening person.
A third said they were “somewhat” of an evening person, while 10% said they “definitely” were. The rest were morning people.
The evening people also tended to be younger, and were inclined to drink and smoke more.
When the researchers followed up in 2018, they learnt that more than 8,700 of the twins had died.
Over the 37 years, the researchers found that the definite night owls had a 9% higher risk of death from all causes – a rate similar to that of the 2018 study.
But this difference was “mainly due to smoking and alcohol”, the study stressed. For example, it found that non-smoker night owls who were light drinkers were no more likely to die earlier than morning people.
Lead author Christer Hublin of the Finnish Institute of Occupational Health told AFP the results showed that night owls can act to lower their risk of an early death.
“Clearly, evening people should critically think about the amount of alcohol and tobacco they are using,” he said.
Independent of other factors, the time when people tend to sleep, known as their chronotype, has “little or no” contribution to their mortality, Hublin added.
Jeevan Fernando, a chronotype researcher at Cambridge University who was not involved in the study, told AFP that while the findings were sound, the research had limitations.
That participants merely self-identified as morning or evening people was “unsatisfactory because it does not include any objective information” unlike more modern methods, he said.
The study also failed to include drugs other than alcohol and tobacco, he said – cocaine, in particular, has been linked to people changing from early to late risers.
Fernando previously led research that showed night owls have worse mental health, particularly anxiety, and that drug use could exacerbate the problem.