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- Cognitive changes are often among the earliest signs of sleep deprivation.
- Increased forgetfulness, trouble concentrating, and irritability may all signal that you’re not getting enough sleep.
- If persistent cognitive symptoms are affecting your daily life, talk to a healthcare provider.
You reread emails multiple times, forget simple tasks like moving laundry to the dryer, or find yourself unusually indecisive about everyday choices, like what to make for dinner. Many people have experienced at least one of these scenarios, and they may all stem from the same underlying cause: not getting enough sleep.
Cognitive changes are often the first signs of sleep deprivation, but they’re easy to dismiss as everyday slip-ups. Here are six common signs to watch for, plus expert-backed tips for getting the rest you need to function at your best.
1. You Can’t Concentrate on What You’re Reading or Watching
According to experts, difficulty focusing and concentrating is one of the most common signs of insufficient sleep. Even avid readers, for example, might find themselves having to reread a page several times when they’re sleep-deprived.
The frontal lobe, which plays a major role in working memory, depends on sleep to function properly. When you don’t get enough, frontal lobe activity decreases. “That results in the brain not being able to take what you’re reading or exposed to and import it into short-term memory,” Ruchir P. Patel, MD, a board-certified sleep physician and the medical director and founder of The Insomnia and Sleep Institute of Arizona, told Health.
2. Your Mood Is Worse
Poor sleep can directly impact emotional regulation, meaning that night after night of inadequate shuteye can leave you feeling persistently down, irritable, anxious, or reactive, said Rupali Drewek, MD, a pediatric pulmonologist, sleep-medicine specialist, and co-medical director of the Sleep Medicine Program at Phoenix Children’s.
“The brain is less able to manage stress and process emotions effectively,” she added. “These changes can occur after even a few nights of poor sleep and often become more noticeable as sleep loss accumulates over time.”
3. You’re Making Simple Mistakes
A decline in attention is one of the more immediate effects of insufficient sleep. Sometimes, losing focus can manifest as a simple typo in an email. Other times, it can result in mistakes that can be downright dangerous, especially when they occur while driving, operating heavy machinery, or performing other high-stakes tasks.
“A lapse of a few seconds is all it takes to miss a highway exit or make an error at work, especially for people who do dangerous jobs that require careful attention,” Eric Anderson, MD, PhD, a board-certified neurologist and chief medical officer at Lin Health, told Health.
4. You’re More Forgetful Than Usual
If you’re misplacing your keys or forgetting meetings, a lack of sleep could be to blame. Poor sleep can have an especially detrimental effect on memory consolidation.
“Sleep plays a key role in organizing and storing memories, so when sleep is limited, the brain has a harder time retaining and recalling information,” Drewek said.
5. You Have Trouble Making Even Simple Decisions
What restaurant to order take-out from on Friday night isn’t a life-or-death decision. But if you’re not well-rested, making those seemingly simple decisions can seem maddeningly difficult. That's because the frontal lobe, which also handles planning and judgment, "doesn’t fire as cleanly," Anderson said. The result? "Something as trivial as picking where to eat starts to feel like real work."
6. You Struggle to Find Words or Follow Conversations
If you’re sleep-deprived, you might find yourself struggling in ordinary conversation, such as blanking on names or losing focus when the other person is speaking.
“The word-finding piece tends to worry people the most,” Anderson said. “I've had patients come in convinced they're developing a neurological disease when the real problem is that they haven't slept properly in months.”
Why Sleep Is So Important for Brain Function
You might assume your brain is “logging off” when you sleep at night, but Anderson said that’s far from the truth. In fact, the brain remains very active during sleep, performing various “housekeeping” tasks related to memory consolidation, attention, emotional regulation, and cognitive processing. The glymphatic system is also most active during sleep, clearing metabolic waste from the brain, including amyloid beta and tau proteins that can accumulate and drive Alzheimer’s disease.
Most people will feel the effects of just one night of bad sleep, but those usually disappear once better sleep resumes. Chronic sleep deprivation is more concerning.
“The pattern I pay closer attention to is the slow accumulation, the person who’s been running on five or six hours for months or years,” Anderson said. “That’s where the damage is quieter and, frankly, more deceptive.”
That’s because people often adapt to feeling tired and may not realize the cognitive toll it’s taking. “One of the better-replicated findings in sleep research is that people in chronic sleep debt rate themselves as basically fine while their performance on objective testing keeps dropping,” Anderson said.
The longer this pattern continues, the more likely that the detrimental effects can spread beyond cognitive health. People who are chronically sleep-deprived have higher rates of depression, anxiety, and heart disease. Anderson added that growing evidence also links chronic sleep to neurodegenerative conditions.
How Much Sleep Do Adults Actually Need?
The American Academy of Sleep Medicine and the Centers for Disease Control and Prevention recommend that adults get at least seven or more hours of sleep per night.
A sleep tracker can help you keep track of how much sleep you’re getting. Beyond that, Patel said a few signs may indicate you’re getting enough quality sleep:
- You fall asleep within 30 minutes.
- You stay asleep for most of the night.
- You feel alert, rested, and clear-headed within 30 minutes of waking up.
On the other hand, if you go to sleep in a neatly made bed but wake up to a tangle of sheets and blankets in the morning, that may be a sign of restless rather than restful sleep. And if you still feel sluggish 30 minutes after waking and even after coffee, you probably didn’t get enough high-quality sleep.
What to Do if You Think Sleep Deprivation Is Affecting Your Brain
If cognitive symptoms are interfering with your daily life, it’s best to speak with a healthcare provider. They can help identify the underlying problem, which may not always be sleep-related. In some cases, cognitive symptoms may be a sign of conditions such as ADHD, depression, thyroid issues, or neurological conditions.
