Role of Genetics in Sleep Patterns
Researchers have identified 351 loci involved in circadian rhythm regulation.
While the sleep schedules are largely influenced by environmental factors such as work or school, previous research has identified 24 loci that likely contribute to whether an individual is a night or morning person. The results of a more recent study published in Nature Communications suggest that the number of genetic factors is likely much higher, with 351 loci found to play a significant role in sleep timing.
To investigate this, researchers analyzed genomes of 700,000 volunteers using data from biobank and 23andMe UK. They then compared the differences in genes with sleep pattern data from both self-reported measures and activity monitors worn by the participants for seven days.
The activity monitors observed and recorded sleep-wake cycles, and unsurprisingly, morning people were found to wake up on average 25 minutes earlier than night owls.
The genetic analysis revealed variations near core circadian rhythm genes - including PER1, PER2, PER3, CRY1, FBXL3 and ARNTL- which were prominent in the suprachiasmatic nucleus of the hypothalamus. This suggests that differences in biochemical feedback mechanisms likely play a role in variations of sleep-wake patterns.
Various other genetic variations were also correlated with the differences between morning and night people. These include variations in RGS16 and INADL (important for the development and function of retinal ganglion cells), FTO (appetite regulation), MADD (insulin secretion), and CYP2A6 (caffeine and nicotine metabolism).
Finally, the researchers investigated possible correlations between sleep patterns and diseases. While no significant correlations were found with type 2 diabetes, insulin levels, and BMI; rates of psychiatric disorders such as depression and schizophrenia were significantly higher in night people.
Despite the fact no correlation was found between the development of metabolic diseases and morningness/eveningness, sleep patterns may still have an effect on physical health. The researchers of this study suggest that circadian misalignment may negatively influence health. For example, genetically programmed night people consistently waking up early (or vice versa) may still be at risk.