If you have to wake someone up from sleep, it means that you can't slept enough.
Dr. Lawrence Epstein told Healthy Living in 2012 that the alarm is the best way to sleep deprive yourself, meaning waking up by yourself could mean that you're simply well-rested, the Huffington Post reported.
Very similar to applications that promise to wake you gently from your slumber, the body also tries to gradually rouse you.
Jan Born, Ph.D said that in anticipation of the start of the day, certain stress-related hormones are produced during the later stages of sleep.
In his 1999 study, Born and his fellow researchers found a hormone called adrenocorticotropin (ACTH) was found in higher levels in the blood when sleepers had an expectation to be woken up at a certain time.
In an experiment, 15 volunteers went to sleep at midnight and were told that they would be woken at 6 a.m. one morning and 9 a.m. on two other mornings.
Born said that when they knew they would be up at 6, then there was an additional increase on top of this gradual increase in ACTH within the period before this expected awakening, which was not found to be the same when they had to be woken up at 9.
According to Luciano DiTacchio, we all operate on internal clocks, but it doesn't mean that just because every human has a clock that every human clock is the same.
He added that variations in certain genes dictate why only some people are natural early risers.