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February 3, 2016

Can Your DNA Determine If You’re a Morning Person or Night Owl?

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    This map shows the proportion of morning people by state based on data from the published study. [23andMe]

    Are you the type of person that jumps out of bed bright-eyed and ready to take on the world? If so, your early morning cheeriness (besides annoying everyone around you) might be hard-coded in your genome. A new genome-wide association study (GWAS) published by the personal genetics company 23andMe identifies an array of genetic variants associated with being a morning person.

    "In this study we set out to discover more about an individual's preference toward early rising and were able to identify the genetic associations with 'morningness' as well as ties to lifestyle patterns and other traits," explained lead study author  Youna Hu, Ph.D., formerly a data sciences engineer at 23andMe at the time the research was being conducted. "This type of study speaks to the power of the 23andMe database, which can yield genetic insights into a variety of conditions and traits, and potentially how those genetic factors are affected by behavior and environment."

    The findings from this study were published recently in Nature Communications through an article entitled “GWAS of 89,283 individuals identifies genetic variants associated with self-reporting of being a morning person.”

    “Circadian rhythms are a nearly universal feature of living organisms and affect almost every biological process. Our innate preference for mornings or evenings is determined by the phase of our circadian rhythms,” the authors wrote. “We conducted a genome-wide association analysis of self-reported morningness, followed by analyses of biological pathways and related phenotypes. We identify 15 significantly associated loci, including seven near established circadian genes.”

    Among the genetic variants that the investigators looked at, they found seven within or near genes previously identified to have a critical role in circadian rhythms. Additionally, four other variants identified were located in or near genes that have a casual relationship circadian rhythm, and the remaining four variants are more of a mystery in the role they play in human sleep cycles.

    “Some circadian rhythm genes we identified have been studied in model organisms, but much less so in humans,” noted co-author David Hinds, Ph.D., principal scientist, and statistical geneticist at 23andMe. “We also identified new genes that have not previously been associated with sleep behavior.”

    Utilizing the vast customer DNA database, the researchers were able to study more than 89,000 genomes, identifying loci near genes associated with morningness, such as HCRTR2 (linked to narcolepsy), FBXL3 (shown to have extended circadian period), and VIP (found to prolong REM sleep). Moreover, the scientists found that the majority (56%) of participants considered themselves night owls, women and adults over age 60 were more likely to be morning people, and morning people are significantly less likely to have insomnia or require more than eight hours of sleep per day. They're also less liable to suffer from depression than individuals who reported being night owls.

    In addition, the 23andMe team found that after normalizing the data for age and sex, morning persons were more likely to have a lower body-mass index (BMI). The researchers urged caution with over-interpretation of this data as it does not imply causation. However, some of the findings may warrant a deeper dive into the biology— for example, variants in the FTO gene associated with obesity were also found to be associated with being a morning person.

    "The beauty of 23andMe is the ability to conduct research on common traits like being a lark or a night owl, which affect everyone yet typically wouldn't receive funding for a study," remarked Dr. Hinds. "With the information we have, we can uncover the genetics behind a variety of conditions and diseases, and hopefully reach a better understanding of how we differ from one another."

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