Night owls, people who are habitually active or wakeful at night, could be at an increased risk of death than morning larks, largely due to smoking and drinking, finds a study.
The study, published in the peer-reviewed journal Chronobiology International, showed that compared to morning types, night owls were younger and drank/smoked more.
They were also less likely to report getting eight hours sleep.
The team tracked nearly 22,976 men and women aged 24 years, for more than 37 years, from 1981 to 2018, in Finland.
Of the total participants, 8,728 had died by 2018 and the chance of dying from any cause was 9 per cent higher among definite night owls compared to early birds.
The findings suggest that lifestyle should be considered.
This is when analysing the impact on health of chronotype -- the body's natural inclination to sleep at a certain time.
The study found that smoking and alcohol largely caused these deaths, not chronotype. This finding was highlighted by the fact non-smokers were at no increased risk of dying.
"Our findings suggest that there is little or no independent contribution of chronotype to mortality," said Dr. 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," Hubli added.
There is increasing evidence that sleep duration and quality, and night shift work affect health.
Earlier, studies have linked night owls with a higher risk of disease, especially heart problems.