A recent July 2019 study by the University of California, San Francisco School of Medicine found that, “While most people struggle with getting out of bed at 4 or 5 a.m., people with advanced sleep phase wake up naturally at this time, rested and ready to take on the day…These extreme early birds tend to function well in the daytime but may have trouble staying awake for social commitments in the evening."
UCSF also found that, “"Generally … it's the people with delayed sleep phase -- those night owls that can't sleep until as late as 7 a.m. -- who are more likely to visit a sleep clinic. They have trouble getting up for work and frequently deal with chronic sleep deprivation,"