Study Links Sleep Patterns, Memory Loss

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Harvard Medical School
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Study Links Sleep Patterns, Memory Loss

News Review From Harvard Medical School

May 2, 2014

News Review From Harvard Medical School -- Study Links Sleep Patterns, Memory Loss

Women who sleep too little or too much in middle age or later may be more likely to have memory problems, a new study suggests. The study included more than 15,000 women, ages 70 or older. All of them were part of the long-term Nurses' Health Study. Women in this study answered questionnaires at regular intervals. Therefore, researchers knew a lot about their health and habits over time. Women who slept fewer than 5 or more than 9 hours each night had worse results on memory tests than those who slept 6 to 8 hours a night. The difference in memory was about equal to another 2 years of aging. Women whose sleep changed by more than 2 hours a night after middle age also had poorer memory than those who slept about the same amount over time. The study results show a link between sleep patterns and memory problems. They do not show that either one caused the other. The Journal of the American Geriatric Society published the study. HealthDay News wrote about it May 1.


By Howard LeWine, M.D.
Harvard Medical School


What Is the Doctor's Reaction?

Too little or too much sleep has been linked with a higher risk of heart and blood vessel diseases, type 2 diabetes and depression. This study adds another possible health risk -- more rapid decline in memory and thinking with age.

The researchers analyzed information from the Nurses' Health Study. This study started in 1976. More than 120,000 female nurses were enrolled. They were 30 to 55 years old when the study began. Using detailed questionnaires about their lifestyles and health, the nurses provided a huge database of information. Researchers have continued to follow what happens to these women as they age.

This particular study focused on length of sleep and performance on tests of memory and thinking. These researchers selected 15,385 of the nurses who had reached age 70 or older and did not have a history of stroke or depression.

The researchers noted significantly worse performance on brain testing in women who slept five hours or fewer per night or nine hours or more per night than for those in the middle. The sweet spot appeared to be about seven hours of sleep per night.

The study was not designed to determine why length of sleep made a difference. But other research provides possible connections. People who continue to be sleep-deprived are more likely to have high blood pressure, diabetes and narrowed blood vessels. So the problem might be decreased blood flow to the brain.

Or it could be that loss of sleep directly affects the brain. Sleep-deprived mice develop more deposits of beta amyloid in the brain than mice allowed to sleep when they want. There are no similar human studies. But there is a strong link between beta amyloid deposits in the brain and declines in memory and thinking, as well as a higher risk of dementia.

What about people who sleep too much? Studies of people who spend more than 9 or 10 hours in bed show that their sleep is often fragmented and  poor in quality. So, for both too little and too much sleep, the actual important number may be the total hours of quality sleep.

Of note, poor sleep quality is very common in people with dementia. Perhaps this is also true for older people with impaired memory and thinking that sometimes leads to dementia. If so, then poorer memory and thinking test performance, such as what was seen in some of the nurses, could reflect brain changes that also caused the altered sleep patterns.

Probably it works both ways. Sleep quality affects memory and thinking, and the brain changes that cause memory and thinking problems also disturb sleep patterns.


What Changes Can I Make Now?

Here are some ways to help you get better sleep:

  • Establish a regular bedtime and a relaxing bedtime routine. Examples might include taking a warm bath or listening to soothing music.
  • Use your bed only for sleeping or lovemaking. Avoid reading and watching television in bed.
  • If you can't sleep after 15 to 20 minutes, get out of bed and go into another room. Read quietly with a dim light. Don't watch television, since the light from the TV has an arousing effect. When you feel sleepy, get back into bed. Don't delay your scheduled wake-up time to make up for lost sleep.
  • Get plenty of exercise. Build up to 45 minutes of moderate exercise nearly every day. Get your exercise early in the day. Try some easy stretching exercises or yoga to relax your muscles and your mind at bedtime.
  • Whenever possible, schedule stressful or demanding tasks early in the day and less challenging activities later. This helps to wind down at the end of your day.
  • Adjust what you eat and drink.
    • Don't go to bed hungry, but don't eat a big meal right before getting into bed. If you want a bedtime snack, keep it bland and light.
    • Limit caffeine and consume none after 2 p.m.
    • To decrease middle-of-the-night urination, don't drink any fluids after dinner.
    • Avoid alcohol after dinnertime. Although many people think of it as a sedative, it can actually impair your sleep.
  • Be sure your bed is comfortable and your bedroom is dark and quiet. Consider a sleep mask or earplugs.
  • Don't let yourself get overheated. Keep the bedroom at a constant, comfortable temperature.
  • Don't take long naps during the day. If you need a nap, restrict it to 20 to 30 minutes in the early afternoon.
  • Turn the alarm clock around so you won't worry that you are still awake.
  • Practice relaxation breathing. Use slow breaths, especially when you exhale.


What Can I Expect Looking to the Future?

No one doubts the importance of sleep to maintain good health. But until recently, we did not realize how much it influences our risk of multiple diseases. Future research will help us learn how to better measure sleep quality and what more can be done to improve it.

Last updated May 02, 2014

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