Why you may be morning or night person

Perhaps you are one of those peppy people who spring into action with the sunrise.

Or perhaps you find that sort of person exhausting, and you do your best work in the evening.

As with so many other human traits, genes seem to play a key role in the answer.

In a new study of 450,000 people, researchers identified 351 genetic variants that were associated with chronotype — the scientific term for when a person prefers to sleep and wake.

Individually, each variant was found to have just a slight connection with whether participants preferred the morning or evening. But collectively, the various genetic markers made an appreciable difference, the authors reported recently in Nature Communications. The 351 telltale snippets of DNA consisted of 24 that had been previously linked to chronotype and 327 new ones.

Some of the new findings were plausible, in that the genes in question were known to be connected to how the body regulates various hormones, while others had no apparent connection to our daily rhythms. Now comes the hard work of sorting out cause and effect, and someday determining which of the genes might be useful in diagnosis and treatment.

Contrary to what has been reported in some previous studies, the researchers found that night owls were no more likely than morning people to suffer from obesity or Type 2 diabetes.