Sleep Glossary
This glossary covers common sleep terms and additional sleep-related terms to help you understand the science behind sleep and improve your sleep quality.
- Insomnia
- Difficulty falling asleep, staying asleep, or waking up too early. This condition often leads to daytime impairment or distress.
- Sleep Hygiene
- Healthy habits and practices that promote consistent, uninterrupted sleep. Good sleep hygiene includes setting a regular sleep schedule, creating a comfortable sleep environment, and avoiding stimulants before bedtime.
- Circadian Rhythm
- Your body's internal clock that regulates the sleep-wake cycle over a 24-hour period. Light exposure, temperature, and daily routines all help synchronize these rhythms.
- Sleep Latency
- The amount of time it takes to transition from full wakefulness to sleep. Short sleep latency indicates falling asleep quickly, while longer durations may signal sleep difficulties.
- Sleep Debt
- The cumulative effect of not getting enough sleep over time. Sleep debt can lead to fatigue, reduced concentration, and other health issues.
- Sleep Efficiency
- The ratio of time spent asleep to time spent in bed. Higher sleep efficiency means most of your time in bed is spent sleeping rather than lying awake.
- Rapid Eye Movement (REM) Sleep
- A sleep stage characterized by rapid eye movements, vivid dreams, and brain activity similar to wakefulness. REM sleep is important for memory consolidation and emotional regulation.
- Non-Rapid Eye Movement (NREM) Sleep
- Represents all sleep stages outside of REM, including light and deep sleep. Deep NREM sleep is crucial for physical restoration and healing.
- Sleep Architecture
- The structure and pattern of sleep cycles (alternating between REM and NREM stages) throughout the night. Disruptions in sleep architecture can affect overall sleep quality.
- Sleep Apnea
- A sleep disorder where breathing repeatedly stops and starts during sleep, often due to blocked airways. This leads to fragmented sleep and may require medical treatment.
- Parasomnias
- Abnormal behaviors or experiences during sleep, such as sleepwalking, night terrors, or sleep talking. They typically occur during NREM sleep.
- Hypersomnia
- A condition characterized by excessive sleepiness during the day, often resulting in long sleep episodes that may still be non-restorative.
- Sleep Diary
- A self-reported log where individuals record details about their sleep patterns, including bedtimes, wake times, perceived sleep quality, and related habits. It helps in identifying and improving sleep issues.
- Sleep Environment
- The physical and environmental factors that affect sleep quality—such as temperature, noise, light, and bedding. Creating a quiet, dark, and cool sleep environment can greatly enhance sleep quality.
- Blue Light
- High-energy visible light emitted by smartphones, computers, and other screens. Exposure to blue light before bedtime can disrupt circadian rhythms and suppress melatonin production.
- Sleep Deprivation
- The condition of not getting enough sleep. It can lead to decreased cognitive function, mood disturbances, and other serious health issues.
- Sleep Quality
- A measure of how well you sleep, including aspects like sleep duration, depth, and restfulness. Good sleep quality means waking up refreshed and maintaining energy throughout the day.
- Chronotype
- Your natural propensity for sleep and wake times—often described as a "morning lark" (early riser) or "night owl" (preferring late nights). Understanding your chronotype can help you schedule your activities in line with your peak energy levels.
- Sleep Inertia
- The groggy, confused feeling that sometimes occurs upon waking. This transitional state can affect cognitive performance and mood for a short time after waking.
Additional Sleep-Related Terms
- Cognitive Behavioral Therapy for Insomnia (CBT-I)
- A structured, evidence-based treatment that helps individuals identify and change negative thought patterns and behaviors surrounding sleep. CBT-I is widely regarded as the first-line treatment for chronic insomnia.
- Delayed Sleep Phase Disorder (DSPD)
- A circadian rhythm disorder in which a person’s sleep is delayed by two or more hours beyond the conventional bedtime. This delay causes difficulty waking up at a desired time, often leading to chronic sleep deprivation.
- Advanced Sleep Phase Disorder (ASPD)
- A condition characterized by an earlier-than-normal sleep onset and wake times. People with ASPD may feel sleepy in the early evening and wake up very early in the morning, which can interfere with social and work schedules.
- Narcolepsy
- A chronic neurological disorder marked by excessive daytime sleepiness, sudden sleep attacks, and, in some cases, episodes of muscle weakness known as cataplexy. It can also include sleep paralysis and vivid hypnagogic hallucinations.
- REM Behavior Disorder (RBD)
- A condition in which the normal muscle paralysis during REM sleep is incomplete or absent, leading to the potential for physically acting out dreams, which can sometimes result in injury.
- Hypnagogia
- The transitional state between full wakefulness and sleep that can include vivid sensory phenomena or brief, surreal images and thoughts, which are normal but may mimic hallucinations.
- Hypnopompic State
- The period during the transition from sleep to wakefulness. Some individuals may experience grogginess or fleeting dream-like images immediately upon waking.
- Restless Legs Syndrome (RLS)
- A neurological disorder characterized by an uncontrollable urge to move the legs, often accompanied by uncomfortable sensations that worsen during periods of rest or in the evening, potentially interfering with sleep.
- Periodic Limb Movement Disorder (PLMD)
- An involuntary disorder that causes repetitive limb movements during sleep. These movements can disrupt the continuity of sleep and reduce overall sleep quality, often without the sleeper's awareness.
- Polysomnography (PSG)
- A comprehensive sleep study that records brain waves, oxygen levels, heart rate, breathing, and eye and leg movements during sleep. It is a key diagnostic tool for evaluating various sleep disorders.
- Actigraphy
- A non-invasive method of monitoring rest and activity cycles using a wearable device, typically on the wrist. Actigraphy helps provide objective data about sleep patterns over time.
- Melatonin
- A hormone produced by the pineal gland in response to darkness, playing a key role in regulating the circadian rhythm. It is also available as an over-the-counter supplement to help adjust sleep schedules.
- Sleep Homeostasis
- The body's drive to sleep, which increases the longer you are awake. This balance between wakefulness and sleep ensures that rest is obtained in proportion to daily activity.
- Sleep Cycle
- The progression through various stages of sleep—from light sleep (NREM) to deep restorative sleep and finally REM sleep. These cycles typically repeat several times each night.
- REM Rebound
- A phenomenon whereby the body compensates for a period of sleep deprivation (or missed REM sleep) by increasing the amount of REM sleep in subsequent cycles.
- Sleep Fragmentation
- The interruption of continuous sleep by repeated awakenings or arousals during the night, which can lead to decreased restorative sleep despite a satisfactory total time in bed.