A comprehensive study of 22,976 Finnish adult twins over a period of 37 years has provided an insight into those who tend to stay up late. The study revealed that night owls are more likely to die at a younger age due to smoking and drinking-related causes rather than how late they go to bed. The study analyzed data from participants’ chronotypes – their tendency to want to sleep or be active at certain times – and identified that being an evening person doesn’t necessarily mean poor sleep habits, but the two often go together. The research found that impaired sleep can lead to a host of mental and physical issues and has also previously been linked to addictions – to nicotine or alcohol, for example.
The study’s participants were identified in 1981, and the researchers followed up in 2018, looking at death rates ascertained through nationwide registers. Factors such as education, BMI, and sleep habits were adjusted for in the analysis, as well as the amount of smoking and drinking each individual did. By 2018, the researchers found that 8,728 of the participants had died. The chance of dying from any cause was 9 percent higher in those who identified themselves as definite evening types than those who were definite morning types. However, non-smokers who also didn’t drink much in this night owl group were at no increased risk of dying from any cause.
The researchers suggest that 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 compared to those who are clearly ‘morning’ persons. Smoking and drinking (leading to alcohol-related diseases as well as alcohol poisoning) were responsible for the extra deaths. The team did not find any increase in cardiovascular-related mortality risk, unlike an earlier study that prompted this one, which involved UK adults who were generally healthier than the average UK population. Here, the cohort’s health was more in line with the general population.
The study suggests that we need to look not just at our sleeping habits but also some of the lifestyle choices that are more likely to happen due to those sleeping habits. Given the associations of chronotype with lifestyle factors that are known to increase the risk of premature morbidity and mortality, the independent contribution of chronotype to mortality is of relevance when providing public health recommendations related to sleep and chronotype. The researchers recommend that there should be more detailed studies involving more people across more countries to help shed more light on this relationship further.