Night owl or early bird: Finnish study links sleep habits to mortality rate

A chronotype refers to an individual's internal biological clock regulating the daily rhythm of their body. It dictates their preferred times for activity and rest. An early chronotype equates to an "early bird," while a late chronotype informally categorizes one as a "night owl".

Genetic and environmental factors condition the chronotype, and it's long been documented that it can influence appetite, physical activity, and body temperature.

The study analyzed the data of 22,976 Finnish adult twins. Remarkably, 42.9% identified themselves as "evening types" or "night types". By the time of this analysis, 8,728 of the survey participants from 1981 had passed away.

From their comprehensive data analysis, the Finnish research team concluded that people with a late chronotype, or 'night owls', tended to die younger than their 'early bird' counterparts. The risk of death was 9% for those who identified themselves as "definitely evening" and rose to 21% for those labeled "definitely nighttime".

The risk of death appeared not directly associated with the chronotype. Still, with lifestyle: once factors such as tobacco smoking and alcohol consumption were considered, the increased risk of death for 'night owls' was no longer apparent.

"Our findings suggest that the chronotype's influence on mortality rates is marginal at best. The increase in mortality risk for those identifying as a distinctly 'evening' person seems to primarily result from higher tobacco and alcohol consumption," said Christer Hublin, the lead author of the study.

The study did not delve into why 'night owls' are more prone to drinking and smoking, but the researchers hypothesize that activities available late at night tend not to be the healthiest. Society's structure often means that activities undertaken after dark aren't usually associated with healthy choices like consuming salads or exercising.