Sleepiness (Excessive Daytime Sleepiness)

Sleepiness vs fatigue

These are often confused but point to different causes:

• Sleepiness: you nod off, your eyelids droop, and you could fall asleep if you sat still. Sleep helps.
• Fatigue: you feel exhausted, weak or drained, but cannot actually fall asleep easily. Common with depression, anemia, chronic illness and long COVID. See fatigue.

Doctors measure sleepiness with the Epworth Sleepiness Scale, which asks how likely you are to doze in 8 everyday situations. A score above 10 out of 24 suggests excessive sleepiness.

Causes of excessive daytime sleepiness

Not enough sleep

The most common cause. About a third of US adults sleep less than 7 hours. Long work hours, screens late at night, caffeine and young children all shorten sleep. Catching up on weekends helps partly, but chronic shortfall builds a sleep debt.

Obstructive sleep apnea

Obstructive sleep apnea is repeated collapse of the throat during sleep, causing breathing pauses that wake the brain many times an hour without you knowing. Clues include loud snoring, witnessed pauses or gasping, morning headaches, waking to urinate at night, high blood pressure and a large neck. It is common in people with obesity but also occurs in slim people and children with large tonsils.

Circadian rhythm problems

• Shift work: working nights or rotating shifts disrupts the body clock.
• Delayed sleep phase: common in teenagers, who cannot fall asleep until very late and struggle to wake.
• Jet lag.

Medicines and substances

Sedating antihistamines, sleeping pills, benzodiazepines, opioids, some antidepressants, antipsychotics, anti-seizure drugs, muscle relaxants and some blood pressure medicines. Alcohol fragments sleep. Cannabis and caffeine withdrawal also cause drowsiness.

Other sleep disorders

• Narcolepsy: overwhelming sleepiness and sudden sleep attacks. Type 1 includes cataplexy, brief muscle weakness triggered by laughter or emotion. Other features are vivid dreams on falling asleep, sleep paralysis and disrupted night sleep. It usually begins in the teens or twenties.
• Idiopathic hypersomnia: long night sleep (often 10 hours or more), extreme difficulty waking (sleep drunkenness) and unrefreshing naps.
• Restless legs syndrome and periodic limb movements: an urge to move the legs at night that delays and disrupts sleep.
• Kleine-Levin syndrome: a rare condition with episodes of extreme sleep lasting days to weeks, mostly in teenage boys.

Medical and mental health conditions

• depression and bipolar disorder
• underactive thyroid
• anemia, diabetes, kidney and liver disease
• heart failure and COPD
• Parkinson's disease, multiple sclerosis and brain injury
• infections, including mono, and recovery from illness
• pregnancy, especially the first trimester

How doctors find the cause

A doctor will ask about your sleep schedule on workdays and days off, snoring, breathing pauses, leg sensations, medicines, alcohol, caffeine, mood and shift work. A sleep diary for 2 weeks is useful. Ask a bed partner what they notice.

Tests may include:

• Blood tests: thyroid function, blood count, iron and ferritin (for restless legs), blood sugar
• Home sleep apnea test: measures breathing, oxygen and heart rate overnight
• Polysomnography: an overnight sleep study in a lab, recording brain waves, breathing, movements and oxygen
• Multiple sleep latency test (MSLT): a series of daytime naps after a sleep study, measuring how fast you fall asleep and whether you enter REM sleep. It is the key test for narcolepsy and idiopathic hypersomnia
• Actigraphy: a wrist device that tracks sleep-wake patterns over 1 to 2 weeks

Treatment

• Insufficient sleep: consistent bed and wake times and 7 to 9 hours in bed. Teens need 8 to 10 hours.
• Sleep apnea: CPAP, oral appliances, weight loss, positional therapy, upper airway stimulation, and newer medicines for those with obesity.
• Circadian disorders: timed light exposure, melatonin at the right time, and schedule changes.
• Medicine review: switching or adjusting sedating drugs with your prescriber.
• Narcolepsy and idiopathic hypersomnia: scheduled naps and wake-promoting medicines such as modafinil, pitolisant, solriamfetol, stimulants or oxybates.
• Treating underlying conditions such as hypothyroidism, depression or iron deficiency.

Sleep habits that help

• keep the same wake time every day, including weekends
• get bright daylight in the morning
• avoid caffeine after early afternoon and alcohol near bedtime
• keep the bedroom cool, dark and quiet, and screens out of bed
• a short nap of 20 minutes or less in the early afternoon can help, but long naps can disrupt night sleep

Drowsy driving

Drowsy driving causes thousands of crashes each year. If you have dozed off at the wheel, do not drive until your sleepiness is treated. Pull over and nap if you feel drowsy on the road. Opening the window or turning up the radio does not work.

Frequently asked questions

Why am I so sleepy all the time?

The most common reason is not getting enough sleep. If you sleep 7 to 9 hours and are still sleepy, consider sleep apnea, depression, medicines, an underactive thyroid, restless legs, shift work, or narcolepsy. A doctor can assess you and arrange a sleep study if needed.

What is the difference between hypersomnia and fatigue?

Hypersomnia means excessive sleepiness: you fall asleep easily or need very long sleep. Fatigue is a lack of energy or exhaustion without necessarily falling asleep. Sleep disorders tend to cause sleepiness, while depression, anemia and chronic illness more often cause fatigue.

Can sleep apnea cause daytime sleepiness?

Yes. Sleep apnea repeatedly interrupts breathing and sleep during the night, often without waking you fully. The result is unrefreshing sleep and daytime sleepiness, sometimes severe. Loud snoring, gasping and morning headaches are clues. CPAP treatment usually improves sleepiness quickly.

What are the signs of narcolepsy?

The main sign is overwhelming daytime sleepiness with sudden sleep attacks. Other features include cataplexy (sudden muscle weakness with laughter or emotion), vivid dream-like images when falling asleep or waking, sleep paralysis and broken night sleep. It is diagnosed with a sleep study and MSLT.

How much sleep do adults need?

Most adults need 7 to 9 hours of sleep a night. Teenagers need 8 to 10 hours and school-age children 9 to 12. Older adults need about 7 to 8 hours. Regularly getting less than 7 hours increases sleepiness and long-term health risks.