Part 5/7:
This pivotal distinction highlights the evolutionary significance of REM sleep, challenging assumptions that the earliest forms of sleep (non-REM) are the most vital for survival.
The Double-Edged Sword of Sleep Duration
Another critical aspect of sleep is the quantity versus quality debate. While the consensus is that 7 to 9 hours of sleep is optimal, exceeding that can paradoxically increase mortality risk. This correlation may not stem from excessive sleep itself but rather from individuals with underlying health issues seeking more sleep in response to illness.