health

Biology & Medicine

Sleep

• Sleep ApneaIn obstructive sleep apnea (OSA), the upper airway repeatedly narrows or collapses during sleep even though the chest is still trying to breathe. Each event can reduce airflow/oxygen and trigger a brief arousal, producing fragmented sleep that the sleeper may not remember.
• Sleep ArchitectureA normal night's sleep is not eight hours of one state. The brain repeatedly cycles through N1 -> N2 -> N3 -> back toward lighter NREM -> REM, with the mixture changing over the night.