People who are night owls or those who stay up late at night and get up late in the day are at risk of dying at an early age compared to the early birds or those who sleep early and also wake up early, according to results of a 37-year follow-up study published in the journal Chronobiology International.1

This study, which was a follow-up of the 2002 Finnish Twin Cohort study, included 23,854 twins from 1981 to 2018. To assess whether they were a morning or an evening person and to what extent, the participants were asked to choose one out of the four responses at the time of enrolment: “clearly a morning or evening person” or “to some extent a morning or evening person”. Deaths till 2018 were ascertained from national registers. Just 10% were clearly evening persons, while 33% were to an extent evening people. Over 29% were clearly morning persons and 27.7% described themselves as morning people to an extent.

There were 13,123 morning persons or early birds (6,354 “clear” and 6769 “to some extent”), while 9853 were evening types or night owls (7591“clear” and 2262 “to some extent”). Compared to the morning persons, the evening people tended to be younger in age and more likely to be consuming alcohol or smoking. A total of 8728 deaths occurred by 2018 when the study ended. Results showed that the all-cause mortality increased by 9% among the clearly evening people compared to the definite morning people with hazard ratio of 1.09. However, the deaths could mostly be attributed to smoking and alcohol intake in larger amounts and not the chronotype of the individual since non-smokers in this group were not at higher risk of death and no association was noted between chronotype and mortality.

This study shows no or minimal independent impact of the chronotype of an individual on mortality suggesting that other factors such as smoking, alcohol or sleep deprivation could be contributing to the increased mortality risk. But the 9% increase in risk of premature death, though small, is significant enough to warrant change in lifestyle and behaviors to reduce one’s risk.

Reference

1. Christer Hublin, et al. Chronotype and mortality - a 37-year follow-up study in Finnish adults. Chronobiol Int. 2023 Jun 15;1-9. doi: 10.1080/07420528.2023.2215342.