Sharpen thinking skills with a better night's sleep

Harvard Health Letter

Getting more sleep can help eliminate fuzzy thinking and restore clarity.

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Getting more sleep can help eliminate fuzzy thinking and restore clarity.

Getting seven to eight hours a night can help you restore clarity and improve memory.

Are you tired of struggling with fuzzy thinking and a faltering memory? Tired may be the key word. "Poor sleep has an adverse impact on thinking," says sleep expert Dr. Lawrence Epstein, an instructor in medicine at Harvard Medical School. "This istrue whether it's due to a lack of sleep or a sleep disorder."

The problem

When people don't get enough sleep, their attention and concentration abilities decline. Their reaction time lengthens, they're inattentive, and they don't respond as well toenvironmental signals. That means they can't take in new information or react to dangerous situations. This is particularly worrisome if you're behind the wheel of a car. "For example, going without sleep for 48 hours impairs cognitive abilities to the samedegree as having a blood alcohol concentration of 0.1%, above the legal limit for driving in every state," says Dr. Epstein, who's also the editor of the Harvard Special Health Report Improving Sleep: A Guide to Getting a Good Night's Rest (available at

A lack of sleep can also contribute to a long list of health problems such as heart disease, high blood pressure, diabetes, obesity, and even early death.


There are many reasons why people don't get enough sleep, chief among them not setting aside enough time. Other common causes include insomnia (difficulty falling or staying asleep); side effects from medication; sleep apnea (a type of breathing disorder during sleep); restless leg syndrome; and chronic conditions such as heartburn, heart disease, thyroid disease, depression, and narcolepsy (a disorder of sleep/wake regulation). Late-night exposure to the light from television and computer screens, as well as smart phones, can also keep us awake, stimulating our brains and making it harder to fall asleep.

Age is another culprit that affects your sleep. You'll find that the older you get, the longer it takes to fall asleep. Sleep quality also becomes poorer, resulting in dozens of awakenings during the night.

What you can do

The good news is that there are plenty of ways to get more sleep. "You really can make up for lost sleep and restore focus and clarity. You can lose the brain fog within a week. But start now; the longer you have bad sleep, the longer it will take to catch up," says Dr. Epstein. He suggests that you aim for seven to eight hours a night. (The idea that older adults can function well on fewer hours is a myth.) Try the following strategies to get started.

  • Check for underlying causes. Some conditions or medications may be interfering with your sleep patterns. Treating a condition or adjusting a medication may be all it takes to restore better sleep.

  • Practice good sleep hygiene. Use your bed for sleep and sex only, block as much noise and light as possible, go to bed and wake at the same times each day, and get out of bed if you haven't fallen asleep within 20 minutes.

  • Supplement with naps. If you can't set aside enough time for sleep at night and are sleepy during the daytime, napping can help. It's best to take one short midday nap before 5 p.m.; naps late in the day can interfere with sleep later. If your problem is difficulty getting to sleep at night, then avoiding daytime sleeping can help increase your sleep drive at bedtime.

  • Exercise earlier, not later. Exercise stimulates the brain, so make sure you finish at least three hours before turning in.

  • Watch your diet. Avoid foods that promote heartburn, and don't eat late at night; lying down after eating promotes sleep-disturbing heartburn. Ban caffeine-packed food and drinks (chocolate, tea, coffee, soda) at least six hours before bedtime. Avoid alcohol for at least two hours before bed. It may make you feel sleepy at first, but several hours later it acts like a stimulant—and interrupts sleep. And don't drink too much water before bedtime, to cut down on trips to the bathroom in the middle of the night.

  • See a sleep specialist. If your own efforts aren't working, you'll want the help of a sleep professional to both diagnose your problem and propose behavioral therapy and possibly drug treatments.