A 37-year study of nearly 23,000 Finnish twins found that lifestyle choices, such as smoking or drinking, affected a person’s health more than their tendency to be a “morning” or “evening” person or chronotype.
However, the study showed that evening types had a slightly increased risk of death than morning types, although staying up late into the night was found to have little effect on how long “night owls” lived.
“Our findings suggest that there is little or no independent contribution of chronotype to mortality,” said lead author Christer Hublin of the Finnish Institute of Occupational Health in Helsinki.
“Furthermore, the increased mortality risk associated with being a definite ‘evening’ person appears to be mainly due to greater consumption of tobacco and alcohol. This is compared to those who are clearly ‘morning’ people,” Hublin said.
This research, led by Jaakko Kaprio of the Finnish Twin Cohort Study at the University of Helsinki, followed 22,976 men and women aged 24 and from 1981 to 2018, taking into account education, daily alcohol consumption, smoking and amount, BMI and height sleep. It is published in the journal Chronobiology International.
At the start of the study, the twins were asked to choose from four possible answers: “I’m clearly a morning person”; ‘I’m somewhat of a morning person’; ‘I’m clearly a night owl’; “I’m somewhat of a night owl. In 2018, when the study ended, the researchers checked national death registries of the participants.
Results showed that compared to morning types (13,123 participants), night owls (9,853) were younger and drank/smoked more. People with “some” eveningness (2,262) were also less likely to report getting 8 hours of sleep. Of the total number of participants by 2018, 8,728 had died.
While the researchers found that the odds of death from any cause were 9 percent higher in “certain” night owls compared to early birds, those deaths were largely caused by smoking and alcohol, not chronotype.
This finding was emphasized by the fact that non-smokers were not at increased risk of death, they said.Causes of death due to alcohol included related diseases as well as accidental alcohol poisoning. 7,591 twins in the study identified as “somewhat” and 2,262 as “definite” evening types. The figures for the morning types were 6,354 and 6,769.
