Hundreds of genetic loci regulate sleep timing in humans

Being a morning person is a behavioral indicator of a person’s underlying circadian rhythm. Using genome-wide data from 697,828 UK Biobank and 23andMe participants, researchers recently increased the number of genetic loci associated with being a morning person from 24 to 351. These variants are associated with objective measures of sleep timing, but not sleep duration or quality. Specifically, the mean sleep timing of the 5% of individuals carrying the most “morningness” alleles is 25 minutes earlier than the 5% carrying the fewest. Moreover, being a morning person is causally associated with better mental health, but does not affect body-mass index or the risk of type 2 diabetes. This research offers new insights into circadian biology and its links to disease in humans. The study, which was partly funded by the NHLBI, was published in the journal Nature Communications.