sleepiness

Sleepiness, or daytime sleepiness, is the subjective sense of the need to sleep or the inability to stay awake. It is not simply fatigue and can occur with adequate sleep if circadian timing or sleep quality is disrupted. Sleepiness can result from insufficient or poor-quality sleep, irregular schedules, or medical and substance-related factors.

Common causes include sleep deprivation, fragmented sleep, sleep disorders such as obstructive sleep apnea and narcolepsy, circadian rhythm disorders (jet lag, shift work), and medications or substances (alcohol, sedatives, antihistamines). Medical conditions such as anemia, thyroid disease, depression, and chronic pain can also contribute.

Physiologically, sleepiness reflects the balance between homeostatic sleep pressure and circadian timing. When wakefulness extends beyond the brain’s available alertness, the urge to sleep grows. Assessment may use the Epworth Sleepiness Scale; objective tests such as the Multiple Sleep Latency Test, polysomnography, and actigraphy help diagnose causes and quantify daytime sleepiness.

Management aims to treat underlying causes and promote sleep health. This includes regular sleep schedules, adequate duration (about seven to nine hours for many adults), a sleep-conducive environment, avoiding alcohol and sedatives, and limiting caffeine late in the day. For specific conditions, treatments may include continuous positive airway pressure for sleep apnea or wakefulness-promoting medications under supervision. Safety is important during periods of high sleepiness.

Persistent sleepiness warrants medical evaluation, as it can impair attention, mood, and safety, increasing the risk of accidents. Public health guidance emphasizes sufficient nightly sleep and addressing sleep disorders to support daytime functioning.