A complete sleep cycle includes light sleep, deep sleep, and rapid eye movement (REM) sleep. Each cycle lasts about 90 minutes and repeats several times each night. If sleep cycles are interrupted or incomplete, you may feel tired even after 8 hours of sleep.
Deep sleep is crucial for physical repair and recovery. If you don't get enough deep sleep, you may feel unrested even after sleeping for 8 hours.
Sleep quality is influenced by your sleep environment, routine, and dietary habits. Excessive use of electronic devices, drinking large amounts of water, or consuming caffeine before bed can lead to poor sleep.
Sleep needs vary from person to person. Some people may need more sleep to feel fully rested, while others may need less.
Chronic illnesses, pain, or side effects of medications can affect sleep quality, even if the duration of sleep is adequate.