People who stay up late and have to drag themselves out of bed are likelier to die younger than those who rise and set with the Sun, researchers said yesterady.
A survey of more than 430,000 people in Britain found that night owls had a 10-percent higher risk of dying in the 6.5-year study period than "larks".
"This is a public health issue that can no longer be ignored," said study co-author Malcolm van Schantz of the University of Surrey -- and argued that "night types" should be allowed to start and finish work later in the day.
"Night owls trying to live in a morning-lark world may (suffer) health consequences," said fellow author Kristen Knutson of the Northwestern University in Chicago.
The duo gathered information on nearly half-a-million people aged 38-73 from a public database.
People in the late-night group were more likely to suffer from psychological disorders, diabetes, and stomach and breathing troubles, and slept fewer hours per night. They were also more likely to smoke, drink alcohol and coffee, and use illegal drugs.
The higher risk may be because "people who are up late have an internal biological clock that doesn't match their external environment," Knutson said.