People with a nocturnal chronotype, known as night owls or owls – while morning ones are larks – are more active at night and have more difficulties adapting to the rhythm imposed by society, since if they have to get up early to study or work do not usually get enough rest. Poor sleep is linked to health problems, yet a new study finds that staying up late has little to do with how long night owls live, and attributes their early death to tobacco and alcohol use.
The chronotype is the natural predisposition of each individual to carry out their daily activities at certain times of the day and the evening type or late chronotype prefers the afternoon and going to bed later. This chronotype has been associated in several studies with a higher probability of suffering from diseases such as diabetes, cardiovascular problems or obesity, and it is also associated with unhealthy dietary habits and a greater tendency to smoke and drink alcohol.
The new research has been carried out by scientists from the Finnish Institute of Occupational Health in Helsinki (Finland) and adult Finnish twins have participated in it, a total of 23,854 people who have been followed for more than 37 years (between 1981 and 2018). . Results published in Chronobiology International have shown that night types have a slightly higher risk of dying than morning types, but this is largely related to smoking and drinking.
“The increased mortality risk associated with being a distinctly nocturnal person appears to be primarily explained by increased tobacco and alcohol use”
“Our findings suggest that there is little or no independent contribution of chronotype to mortality,” says Dr. Christer Hublin, from the Finnish Institute of Occupational Health in Helsinki and the study author. “Furthermore, the increased mortality risk associated with being a distinctly nocturnal person appears to be primarily explained by increased tobacco and alcohol use. This is comparable in those who are clearly morning people.”
Evening non-smokers had no increased risk of death
There is increasing evidence that the duration and quality of sleep and working the night shift affect health. Previous studies have linked the nocturnal chronotype with an increased risk of disease, especially heart problems. For example, data published in 2018 from the UK Biobank Chronotype and Mortality Study, in which participants were followed for 6.5 years, found that evening types have a small increased risk of death from any cause, including cardiac pathologies.
The authors of the new study decided to extend the follow-up to include factors that were not measured in that study, such as alcohol consumption and how much they smoked. Participants were asked to try to “assess to what extent you are a morning person or an evening person.” ”, with four response alternatives: “Clearly, I am a morning person”; “I am to some extent a morning person”; “I am clearly a night person”; “I am to some extent a night person.”
Four groups were thus defined: 7,591 of the twins identified as ‘to some extent’ and 2,262 as ‘definite’ night types. The numbers of morning individuals were 6,354 and 6,769, respectively. Compared to early risers, night owls were younger and drank and smoked more. Types classified as nocturnal were also less likely to report getting 8 hours of sleep.
The researchers took into account education, daily alcohol consumption, smoking status and number, BMI (body mass index), and sleep duration. Of the total number of participants, 8,728 had died in 2018 and the probability of dying from any cause was 9% higher among those who defined themselves as clearly night owls compared to early risers.
However, the study found that smoking and drinking alcohol largely caused these deaths, not the chronotype. This finding was highlighted by the fact that non-smokers did not have an increased risk of dying. Causes of alcohol-related deaths included alcohol-related illnesses, as well as accidental alcohol poisoning.
Dr. Jaakko Kaprio, co-director of the research, notes that their findings are best extrapolated to society as a whole because the health of their participants was no different from that of the general population, while the health of individuals included in the UK Biobank were better than average. They highlight access to comprehensive data on lifestyle factors as a strength of his research, although it is important to note that the findings were based on self-reported data when answering a question.
