According to the research we have so far, light sleep does not contribute any major physical or cognitive functions or mechanisms. In other words, there are no recommended minimum hours of light sleep required for each night. Deep sleep and REM sleep are generally understood to be more critical.
However, light sleep is not “bad.” Although not as important as the other phases, it is still restful and refreshing and serves as a practical and necessary transition period between wakefulness, deep sleep, and REM sleep phases. It’s not possible for the brain and the body to safely jump from the high-frequency, high-energy brain activity of wakefulness to the low-frequency brain activity of deep sleep, or vice versa.