Most healthy adults need between seven and nine hours of sleep each night. While an occasional night of poor sleep is not harmful, ongoing sleep difficulties that affect daily life are considered sleep problems. Sleep consists of four stages, cycling every 90 to 120 minutes:
Stage 1: Falling asleep
This initial stage is a light transition to sleep, where muscles relax, heart rate slows, and brain activity decreases.
Stage 2: Light sleep
During light sleep, you are asleep but can still be easily awakened. The body continues to relax as heart rate, blood pressure, and temperature drop.
Stage 3: Deep sleep
Deep sleep is restorative, allowing the body to recover. It supports muscle repair, organ growth, and memory consolidation.
Stage 4: REM sleep
Rapid Eye Movement (REM) sleep is marked by heightened brain activity and is the stage where most dreaming occurs. Blood pressure and heart rate increase during REM, making it a vital phase for mental restoration.
These stages repeat throughout the night, supporting physical and mental well-being. Inadequate sleep can lead to irritability, concentration difficulties, and increased health risks.