A 37-year long study on nearly 23,000 Finnish twins has found that lifestyle choices such as choosing to smoke or drink impacted one’s health, more than one’s tendency to be a ‘morning’ or ‘evening’ person or chronotype, impact health.
The study, however, showed that evening types had a slightly increased risk of dying than morning types, even as staying up late at night was found to have little impact on how long a life ‘night owls’ lived.
“Our findings suggest that there is little or no independent contribution of chronotype to mortality,” said author Christer Hublin, from the Finnish Institute of Occupational Health in Helsinki.
“In addition, the increased risk of mortality associated with being a clearly ‘evening’ person appears to be mainly accounted for by a larger consumption of tobacco and alcohol. This is compared to those who are clearly ‘morning’ persons,” said Hublin.
This research, co-led by Jaakko Kaprio, from the Finnish Twin Cohort study at the University of Helsinki, followed 22,976 men and women aged 24 years and from 1981 to 2018, taking into account education, daily alcohol consumption, smoking status and quantity, BMI, and sleep duration. It is published in the journal Chronobiology International.
At the start of the study, the twins were asked to pick from four possible responses: ‘I am clearly a morning person’; ‘I am to some extent a morning person’; ‘I am clearly an evening person’; ‘I am to some extent an evening person’. In 2018, when the study ended, the researchers checked with the nationwide registers for participant deaths.
Results showed that compared to morning types (13,123 participants), night owls (9,853) were younger and drank/smoked more ‘Definite’ evening people (2,262) were also less likely to report getting 8 hours sleep.
Of the total participants, 8,728 had died by 2018.
While the researchers found the chance of dying from any cause to be 9 per cent higher among ‘definite’ night owls compared to early birds, smoking and alcohol had largely caused these deaths, not chronotype.
This finding was highlighted by the fact non-smokers were at no increased risk of dying, they said.
The causes of deaths from alcohol included related disease as well as from accidental alcohol poisoning.
7,591 of the twins in the study had identified as ‘to some extent’ and 2,262 as ‘definite’ evening types. The figures for morning types were 6,354 and 6,769, respectively