As we age, our sleep patterns change. We've all heard the complaints: "I wake up in the middle of the night and can't get back to sleep!"

Some sleep experts estimate that as many as 40 percent of older adults suffer sleeping problems such as sleep apnea and insomnia. Now, researchers have found a link between disrupted sleep and cognitive decline.

Psychiatrist Kristine Yaffe of the University of California, San Francisco, runs a memory disorders clinic and studies people who are at risk of developing dementia and cognitive impairment.

She says many of her older patients "either have difficulty falling asleep, waking up on and off throughout the night, or feeling tired in the day" and have to nap a lot.

Yaffe recently conducted a series of studies evaluating more than 1,300 adults older than 75, initially assessing their sleep patterns and, five years later, their cognitive abilities. She found that those with sleep-disordered breathing or sleep apnea had more than twice the odds of developing dementia years later.

Those who developed disruptions of their circadian rhythm were also at increased risk. So were those who awoke throughout the night, tossing and turning. The findings were presented at the annual conference of the Alzheimer's Association.

It's critical to note that Yaffe's findings show only an "association" between sleep problems and dementia. Far more study is needed to confirm these findings and investigate possible reasons for this connection.

In the meantime, Yaffe says there is something of a silver lining. Older adults can be routinely screened for sleep problems. And, if diagnosed early, treatments can help them sleep better and possibly, down the line, reduce the risk of cognitive decline.

Psychologist Sonia Ancoli-Israel studies sleep and aging at the University of California, San Diego. Ancoli-Israel points to a variety of techniques to help people literally relearn how to go to sleep.

"We want to take a person who has negative associations with the bed — 'Oh, my God, I know I'm not going to be able to sleep' — and turn them around so that they look at the bed and they go 'Ah, sleep,' " she says.

One of the most effective strategies is to actually restrict the amount of time people sleep, starting with very little time — say, five hours — and slowly adding 15-minute increments until the recommended eight hours is reached. It's a slow process, says Ancoli-Israel, taking up to one month. But "it's very, very effective and lasts for years," she says.

Then, there's "stimulus control," in which, as she puts it, "you're not allowed to do anything in bed but sleep — sleep and sex, that's it."

"You can't pay bills in bed, you don't take your computer or your iPhone or iPad to bed, you don't watch TV in bed, you don't read in bed."

If you don't fall asleep in 20 minutes, get out of bed and do something relaxing. "Don't watch a suspenseful movie or read a suspenseful book," she says. "Watch something a little more boring, read something a little more boring, so that when you get sleepy, you're willing to set it down and go to bed."

As for the clock, get rid of it. "The first thing you do when you wake up at night, you look at the clock," Ancoli-Israel says. "And in order to look at the clock, you have to lift your head, open your eyes, but, more important, you have to take yourself from transitional sleep to full awakening to comprehend that its 1:10 in the morning and you want to be asleep." Full awakening, of course, makes it difficult to get back to sleep.

If you need the alarm, cover the clock, she says, or put it under the bed. You'll still hear it go off.

Now, there's another sleep difficulty faced by older adults. Natural circadian rhythms change. Sleep is controlled in part by our core body temperature, which drops at night when we get sleepy and rises in the morning, and that's when we wake up.

These patterns change throughout our lives. Teenagers' body temperature drops late in the evening, so they don't get tired till around midnight and don't naturally wake up till late morning, causing many a parent to complain that their teen is sleeping the day away. In fact, they're simply following their biological clock.

For older adults, it's the opposite. Their body temperature drops really early in the evening, around 8 p.m., and rises really early in the morning, around 4 a.m. If your lifestyle allows it, Ancoli-Israel says it's just fine to go to bed early and get up at 4 a.m.

But for many people, evening social events take precedence. In that case, Ancoli-Israel suggests light. "Light is the strongest cue our body has to know when to go to sleep and when to get up. Lots of light exposure during the day helps us have a strong biological clock," she says.

And the best source of light is the sun. Ancoli-Israel says a late afternoon or early evening walk, when the sun is still out, is best. That delays the circadian rhythm and helps people stay alert later in the evening and sleep longer in the morning.

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