US researchers have identified a genetic variant that explains the preference of an individual to mornings or nights.
The researchers identified 15 locations in DNA (loci) linked with "morningness", and asserted that morningness is governed by differences in circadian rhythm or biological clock.
The study provides genetic insights into a variety of conditions and traits, and how those genetic factors are affected by behaviour and environment, said the researchers.
"In this study we set out to discover more about an individual's preference towards early rising and were able to identify the genetic associations with 'morningness' as well as ties to lifestyle patterns and other traits," said lead author Youna Hu from 23andMe -- a leading personal genetics company in California, the US.
Individuals who are early are significantly less likely to have insomnia, or require more than eight hours of sleep per day, and less likely to suffer from depression than individuals who reported being "night owls", the researchers said.
After taking into account the effect of age and sex, morning persons are likely to have lower body mass index (BMI), the study said.
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The majority (56 percent) of participants consider themselves night owls. And women and adults over age 60 are more likely to be morning people, the findings showed.
Published in the journal Nature Communications, the study of more than 89,000 participants found that seven of the loci associated with morningness are near genes previously known to be involved in circadian rhythm and found to prolong rapid eye movement (REM) sleep.