Alzheimer’s Disease: Are You, Poor Sleeper, at Risk?

I talk quite a bit about dementia and Alzheimer’s disease with family and friends. Our parents are drifting into cognitive impairment, asking the same questions again and again and struggling to find words to express themselves, and we wonder if we’re destined for the same fate.

The concern may be justified in middle-aged adults with chronically poor sleep, according to new research on sleep and two proteins involved in Alzheimer’s disease. Here’s more about the study and its relevance to people with insomnia and other sleep disorders.

Proteins linked to Alzheimer's a function of insufficient deep sleepI talk quite a bit about dementia and Alzheimer’s disease with family and friends. Our parents are drifting into cognitive impairment, asking the same questions again and again and struggling to find words to express themselves, and we wonder if we’re destined for the same fate.

The concern may be justified in middle-aged adults with chronically poor sleep, according to new research on sleep and two proteins involved in Alzheimer’s disease. Here’s more about the study and its relevance to people with insomnia and other sleep disorders.

Poor Sleep and Cognitive Impairment

Previous research has shown that poor sleep increases the risk of cognitive impairment. And mild cognitive impairment—trouble thinking and memory loss—is one of the first signs of Alzheimer’s disease. The cognitive declines and memory problems gradually worsen as deposits of two proteins—amyloid beta and tau—grow thicker and thicker, causing brain tissue to atrophy and die. To date the disease is irreversible.

But “poor sleep” can take different shapes and forms:

  • Sleep apnea, or pauses in breathing that occur repeatedly throughout the night, leaving sleepers feeling unrested in the morning.
  • Restless legs syndrome, in which sleep is disrupted by involuntary leg movements in the first half of the night.
  • Insomnia, consisting of trouble falling asleep, staying asleep, or waking up early in the morning, and related daytime complaints

Which feature of some or all of these sleep disorders might hasten development of amyloid plaques in the brain? The researchers suspected the problem had to do with deep, or slow wave, sleep, which is associated with feeling rested and restored in the morning. So they set out to see if disrupted slow wave sleep would bring about increased levels of amyloid beta in the brain.

Who They Studied, What They Did

Seventeen healthy adults ages 35 to 65 participated in the study, none with sleep problems or cognitive impairment. Each participant wore a wrist watch-type device to monitor their sleep. After several nights of wearing the device, participants spent a night in a sleep lab. There, they underwent a sleep study that involved wearing headphones.

Half of the participants were allowed to sleep without interruption. The other half experienced sleep disruption. Every time they entered deep sleep, they were subjected to beeps that grew louder and louder until their slow waves disappeared and were replaced by brain waves characteristic of lighter sleep.

The participants subjected to the beeps reported feeling tired and unrefreshed in the morning although they slept as long as usual. Most did not recall awakening during the night. All participants underwent a spinal tap so researchers could test for levels of amyloid beta and tau in the spinal fluid.

The procedure was repeated a month later, when the participants originally allowed to sleep uninterruptedly were subjected to the beeps and the others were allowed to sleep without interruption. Another spinal tap was conducted in the morning to measure protein levels.

Disrupted Deep Sleep and Harmful Proteins in the Brain

The results supported researchers’ contention about the effects of disrupted slow wave sleep:

  1. Participants’ amyloid beta levels were up by 10 percent after a single night of disrupted slow wave sleep
  2. In addition, levels of tau were significantly higher in participants whose wrist monitors showed they’d slept poorly during the week before the spinal tap

So disrupted slow wave sleep increased amyloid beta levels after just one night and tau levels after several days of poor sleep. Evidently, one function of slow wave sleep is to help rid the brain of byproducts that collect there during the day. When deep sleep is compromised, amyloid beta and tau start to accumulate. Development of cognitive impairment and Alzheimer’s is then more likely to occur.

Alzheimer’s and Poor Sleep in Perspective

So does the overall risk of developing Alzheimer’s increase with every poor night’s sleep? Probably not. Lead author Yo-El S. Ju, cited in a Washington University press release, said it’s unlikely that a single night or even a week of poor sleep has much effect on overall risk of developing Alzheimer’s disease. Amyloid beta and tau levels probably go back down the next time the person has a good night’s sleep, she said.

It’s people with chronic, untreated sleep disorders who should be concerned. Here, too, a dose of perspective is in order. Slow wave sleep occurs during the first half of the night. People who suspect they have sleep apnea, which occurs throughout the night, or restless legs syndrome, which occurs during the first half of the night, would be wise to see a sleep specialist for diagnosis and treatment.

People with chronic insomnia may have cause for concern as well—and maybe not so much. These investigators did not find that excess amyloid beta and tau had anything to do with sleep duration or sleep efficiency. Further, it’s never been shown that the main problem for people with insomnia is insufficient slow wave sleep. Some insomniacs experience a reduced percentage of slow wave sleep. Yet in others, slow wave sleep is intact.

The underlying problem in insomnia may instead involve restless REM sleep, which typically occurs in the second half of the night. It may have nothing to do with the development of amyloid plaques in the brain.

In any event, chronic insomnia can be treated (although the causes remain largely unknown). Click on “insomnia treatment” in the tag cloud to the right for more information.

Exercise Improves Sleep, Preserves Mental Fitness

You may have been a couch potato for most of your life, but now, if you’re middle-aged and envisioning a healthy retirement, you’d better change your ways.

Moderate-to-vigorous exercise can mitigate some effects of aging, including poor sleep quality and cognitive decline. Research generally supports this claim, so especially if you’re prone to insomnia, you’ll want to check this out.

Insomnia and mental decline can be alleviated with exercise
Me, returning from my first bike ride this year

You may have been a couch potato for most of your life, but now, if you’re middle-aged and envisioning a healthy retirement, you’d better change your ways.

Moderate-to-vigorous exercise can mitigate some effects of aging, including poor sleep quality and cognitive decline. Research generally supports this claim, so especially if you’re prone to insomnia, you’ll want to check this out.

Age-Related Sleep Problems and Exercise

Sleep tends to be less robust as we age. Middle-aged and older adults get less deep sleep (the restorative stuff) than younger people. Our sleep is less efficient, too, peppered with wake-ups during the night. In the morning, we wake up feeling less rested, with fewer resources to meet the demands of the day.

Investigators are now looking at lifestyle factors that might alleviate aged-related sleep problems. A majority of studies suggest that both male and female exercisers tend to experience better sleep quality and fall asleep more quickly than people who don’t exercise.

Newer Data From Objective Tests

The majority of such studies are based on reports from participants rather than objective tests. In two more recent studies, investigators used objective measures to assess the relationship between participants’ level of physical activity and their sleep.

The SWAN Sleep Study was an observational study involving 339 middle-aged women. Over 6 years, investigators collected data on their activity level in three domains: (1) Active Living (activities like watching TV and walking to work), (2) Household/Caregiving (housework and childcare), and (3) Sports/Exercise (recreational activities and sports).

Toward the end of the 6-year period, the women underwent in-home polysomnography (a sleep study) every night during one entire menstrual cycle or 35 days, whichever was shorter. They also kept sleep diaries and filled out sleep-related questionnaires.

Altogether this made for a lot of data on a lot of women. The findings reported here are both significant and clinically important:

  • Activities in the Active Living and Household/Caregiving categories had little impact on women’s sleep. Women typically spend a lot of time doing these activities, yet they may not be vigorous enough to affect our sleep.
  • Women with high Sports/Exercise activity over the 6-year period experienced better sleep, especially on measures of sleep quality and sleep continuity.
  • Greater recent Sports/Exercise activity was associated with better sleep quality and better sleep continuity—and more deep sleep (insomnia sufferers, take note!).

What About Men?

Routine exercise has similar benefits for men, a small exercise intervention study showed. Via polysomnography, the sleep of 13 men aged 60 to 67 was assessed 3 nights before and 3 nights after they participated in a 16-week exercise program. The program consisted of regular 60-minute workouts on the treadmill. The workouts were fairly rigorous and the results, impressive. Compared with their sleep before starting the exercise program, by the end of the program the men’s sleep

  • had significantly greater continuity. Acute exercise reduced their nighttime wakefulness by 30%.
  • was significantly deeper. On nights following exercise, they experienced a 71% increase in slow-wave (deep) sleep. (That 71% is not a typo, by the way!)

Exercise Protects Mental Fitness

If the sleep benefits of exercise don’t move you to action, maybe the high cost of inactivity to your brain will. Regular exercise helps improve cognitive function and protects against cognitive decline. How it does so has yet to be worked out, but one theory holds that exercise has a beneficial effect on the brain due to its positive effect on cerebral blood flow. For optimal functioning the brain has to have adequate blood flow. Moderate-intensity exercise increases blood flow to the brain in healthy adults.

But blood vessels may lose their ability to respond normally in the brain and elsewhere, a situation called vascular dysfunction, which is associated with cardiovascular disease. Systemic vascular dysfunction will likely reduce blood flow to the brain and manifest as cognitive impairment.

“Vascular dysfunction and altered blood flow regulation may be a key link between cardiovascular disease and cognitive decline,” writes Jill N. Barnes in a paper titled Exercise, Cognitive Function, and Aging.

Protecting vascular health—which typically declines with age—may also protect against cognitive decline. Barnes cites a few studies that suggest that exercise is the key to protecting vascular functioning. A few other human studies show that both aerobic exercise and strength training help maintain cognitive fitness. In addition, animal studies have shown that sustained aerobic exercise promotes the growth of new nerve cells in the hippocampus, a part of the brain associated with memory.

So particularly if you’re middle aged or older and prone to inactivity, check into starting an exercise program now. It will improve your physical and mental health and—perhaps more relevant if you’re looking for help with insomnia—it will likely improve your sleep.

Pink Noise Enhances Sleep and Memory

An acoustic device may be able to accomplish for older adults what sleeping pills still cannot: enhance both sleep and memory.

Researchers at Northwestern University in Chicago conducted a study of 13 healthy older adults whose sleep deepened and whose recall of word pairs improved with timed acoustic stimulation at night. The discovery holds promise not just for older people with insomnia but also for everyone concerned about aging and memory impairment.

Sleep may be deeper and memory better by listening to timed exposure to pink noise at nightAn acoustic device may be able to accomplish for older adults what sleeping pills still cannot: enhance both sleep and memory.

Researchers at Northwestern University in Chicago conducted a study of 13 healthy older adults whose sleep deepened and whose recall of word pairs improved with timed acoustic stimulation at night. The discovery holds promise not just for older people with insomnia but also for everyone concerned about aging and memory impairment.

Older Research on Deep Sleep and Memory

Previous research has shown that memory consolidation for facts and events takes place mainly during deep, or slow wave, sleep. Overnight new memories are replayed in the brain and processed so they become more resistant to loss and deterioration. In this way, sleep actually improves our mental hold on learning that took place the day before.

Research has also shown that gentle sound stimulation at night—pink noise, specifically, which sounds like rushing water—can increase slow wave activity and improve the recall of words. Three prior studies were conducted on young adults, all with positive results. The Northwestern team wanted to see if older adults, who typically get less deep sleep and whose risk of memory impairment is greater, would reap the same benefits.

How They Conducted This Study

Thirteen adults ages 60 to 84 participated in this randomized controlled study. They spent two nights in a sleep lab spaced one to two weeks apart.

The procedure on both nights was identical in the eyes of the participants. They wore a device consisting in part of an electrode cap that would record their brain activity as they cycled through the different stages of sleep.

About 90 minutes before bedtime, participants were shown a series of 88 word pairs on a computer screen and told to memorize the pairs. Then, in random order, they were shown one word and asked to recall the other half of the pair (e.g., energy: oil). Then they put on soft headphones and went to sleep.

An hour after waking up, each participant was again shown the words, in random order, and asked to recall the paired word.

What participants did not know was on which of the two nights they were going to be exposed to several pulses of pink noise during slow wave sleep. The noise wasn’t loud enough to wake them up; nor was it faint enough for their brains to tune out. There was no noise exposure on the other night.

A Relationship Between Pink Noise, Sleep, and Memory

The results of the study were similar to results in the studies of young adults. Although participants’ overall sleep structure did not change,

  • When acoustic stimulation was delivered, it increased slow wave activity in the brain.
  • The acoustic stimulation improved participants’ morning recall of words. As predicted, they remembered more words in the morning than they had the night before. But after acoustic stimulation, on average they remembered 9 more words than they had the night before, as compared with recall on the morning following the night without noise, when on average they remembered only 3 more words.
  • The relative change in slow wave activity predicted the improvement in memory.

Tracking Brain Activity to Time Noise Exposure Right

This study might lead to the conclusion that older adults could sleep more soundly and smarten up by using pink noise sound apps at night. Maybe so and maybe not. Exposed to continuous low-level sound, the brain might decide to tune it out.

The beauty of this new device lies in the way it individualizes and maximizes the effects of treatment. It uses an automated algorithm to monitor slow waves produced in the brain and deliver acoustic stimuli at just the right time. This feature—called a phase-locked loop—was found in previous studies to increase slow wave activity and memory consolidation in young adults during daytime naps. So despite age-related changes in sleep and memory (and whether or not insomnia is involved), older adults stand to gain a lot if and when the device comes to market.

Northwestern University currently has a patent pending but researchers say more testing is needed before the device is ready for general use. Still, it’s nice to know that some researchers studying sleep and memory are thinking outside the box.

Can Foods Improve Sleep Quality?

With sleeping pills getting bad press these days, the race is on to find more nonpharmacologic, alternative treatments for insomnia. One area of interest is diet and nutrition. Are there foods that could help us sleep?

The evidence for a relationship between food and sleep is mixed, say authors that reviewed 21 studies on the topic. But a new randomized controlled study of the effects of diet on sleep suggests that foods high in fiber, saturated fat, and sugar may significantly affect the quality of our sleep.

Sleep quality is affected by dietary fiber, saturated fat, and sugarWith sleeping pills getting bad press these days, the race is on to find more nonpharmacologic, alternative treatments for insomnia. One area of interest is diet and nutrition. Are there foods that could help us sleep?

The evidence for a relationship between food and sleep is mixed, say authors that reviewed 21 studies on the topic. But a new randomized controlled study of the effects of diet on sleep suggests that foods high in fiber, saturated fat, and sugar may significantly affect the quality of our sleep.

Measuring Sleep Depth and Duration

Twenty-six people (none with insomnia) participated in the study. All were normal sleepers, averaging 7 to 9 hours of a night.

The study was conducted in two 6-day periods. During one of these periods, the participants were allowed to sleep up to 9 hours a night every night. During the other 6-day period, their sleep was restricted to 4 hours a night for the first 4 nights, followed by a night of unrestricted sleep.

Participants underwent polysomnography—the test recording brain waves and the depth and nature of sleep—every night. Investigators kept track of variables such as total sleep time, sleep onset latency, number of arousals, and deep sleep.

A Controlled Diet

On the first 4 days of each 6-day period, participants were given enough food to meet their need for calories, but the type of food was controlled. On days of the controlled diet, participants were given food in which

  • 31% of the energy came from fat ( 7.5% from saturated fat),
  • 53% of the energy came from carbohydrates, and
  • 17% of the energy came from protein.

On days 5 and 6, study participants could eat the foods they wanted as long as the nutrient content could be readily determined.

Participants underwent other testing as well, including a glucose tolerance test and a blood test.

Fiber, Saturated Fat, and Sugar Alter Sleep Quality

Study results showed that participants consumed significantly more calories on the day after 4 nights of restricted sleep (a day when they could eat as much as they wanted) than during the period when they were allowed to sleep as much as they normally slept. This confirms the results of other research showing that people who don’t get enough sleep tend to eat more and gain weight.

But after statistical analysis, investigators identified a few dietary variables that were associated with changes in sleep quality:

  • Eating more foods high in fiber was associated with less stage 1 sleep (the lightest stage) and more slow wave sleep (or deep sleep). Foods high in fiber include fruit with skin; whole grains; legumes, nuts, and seeds; and vegetables such as artichokes, peas, and broccoli.
  • Eating more foods high in saturated fat predicted less deep sleep. Foods high in saturated fat include meat, cheese, and other dairy products.
  • Eating more foods high in sugar and non-sugar/non-fiber carbohydrates was associated with more nighttime wake-ups. Foods high in sugar and starch include fruit juice, pop, white rice, pasta, potatoes.

The study has limitations, including its small size and short duration. Also, whether the results would be the same for people with insomnia is unknown.

But the implications of the study reinforce what we hear elsewhere. For health reasons, we’re told to cut down on meat, dairy, and processed foods, and increase our intake of fruit and vegetables. Now there’s another reason to do that: it may improve the quality of our sleep.

Insomnia and Napping: No One-Size-Fits-All Prescription

If you have insomnia, you’ve probably heard it’s best to avoid naps. Maybe you heard it from your doctor in a conversation about the rules of “good sleep hygiene,” or maybe you read it in a magazine. Is the advice to refrain from napping really sound advice and, if so, do you have to swear off napping completely to get a better night’s rest?

There are no one-size-fits-all answers to these questions, say researchers who recently reviewed the evidence behind the recommendation to avoid napping and other sleep-related do’s and don’ts. It depends on your age and situation.

Chronic insomniacs should avoid naps, but people whose sleep problems are less severe need not abstainIf you have insomnia, you’ve probably heard it’s best to avoid naps. Maybe you heard it from your doctor in a conversation about the rules of “good sleep hygiene,” or maybe you read it in a magazine. Is the advice to refrain from napping really sound advice and, if so, do you have to swear off napping completely to get a better night’s rest?

There are no one-size-fits-all answers to these questions, say researchers who recently reviewed the evidence behind the recommendation to avoid napping and other sleep-related do’s and don’ts. It depends on your age and situation.

Chronic Insomnia

If you’ve got chronic insomnia (trouble sleeping at least 3 times a week for at least 3 months accompanied by daytime impairments), then forgoing naps may improve your sleep. Research has shown that the pressure to sleep builds higher and higher during the daytime and is released at night during deep sleep. Napping during the daytime may result in the early discharge of some of the sleep pressure. This can make it harder for people with persistent insomnia to fall asleep and stay asleep at night.

Accordingly, if you go through cognitive-behavioral therapy (CBT) for insomnia, you’ll be asked to refrain from napping during treatment. The fact that CBT works as well as it does supports the idea that cutting out naps is a useful strategy for insomniacs who want to improve their sleep at night.

What should you do if you can’t survive without a nap? Sleep therapists may recommend the following:

  1. Keep the nap short—30 minutes or less—to avoid descending into deep sleep
  2. Refrain from naps in the evening, when the pressure to sleep is high.

Mild or Occasional Sleep Problems

If you’re basically healthy and your sleep problems are occasional or less severe, then it’s not so clear that cutting out naps will help. Nor is it evident, in insomnia associated with aging, that the benefits of napping don’t compare favorably next to the difficulties created when the nap is cut out.

Napping occurs more frequently as people age, so the subjects in most studies of napping in naturalistic settings have been older adults. The results have not been consistent from one study to the next. However, the majority have not identified a significant association between daytime napping and nighttime sleep in older adults. Nor did researchers who conducted a study involving healthy young and middle-aged nappers find such an association.

Adding a Nap

Researchers have also looked at how adding a nap into people’s daily schedules affects their sleep at night—mostly in middle-aged and older adults. Here, too, the results are mixed. In some studies, naps resulted in shorter, less efficient sleep at night; in other studies, the naps had absolutely no effect on nocturnal sleep.

Of note is the fact that no researchers have ever conducted a study to determine whether depriving habitual nappers of their naps actually improves their sleep at night.

So the recommendation not to nap that appears on the list of habits consistent with good sleep hygiene? Unless you have chronic insomnia, for now, take this recommendation with a grain of salt. There may be other more effective paths to reliably sounder sleep.

If you take naps, what effect do they have on your sleep at night?

Smoking and Your Sleep

As habits go, cigarette smoking is one of the riskiest. Despite the many reasons people give for smoking—it provides relaxation and stress relief, increased stamina and concentration, weight control—the costs are steep. Cancer, emphysema, and heart disease top the list.

Whether smoking also causes insomnia remains to be seen. But research has shown it harms sleep quality. Two teams of scientists—one at Johns Hopkins University in Baltimore and the other based in Freiburg, Germany—set out to measure smoking’s impact on sleep, and here is what they found.

Smoking degrades the quality of your sleep and may cause insomnia.As habits go, cigarette smoking is one of the riskiest. Despite the many reasons people give for smoking—it provides relaxation and stress relief, increased stamina and focus, weight control—the costs are steep. Cancer, emphysema, and heart disease top the list.

Whether smoking also causes insomnia remains to be seen. But research has shown it harms sleep quality. And one reason it’s so hard to quit smoking is the trouble sleeping many smokers experience during nicotine withdrawal: thirty-nine percent of smokers report having insomnia when they try to quit smoking. Using polysomnography, two teams of scientists—one at Johns Hopkins University in Baltimore and the other based in Freiburg, Germany—set out to measure smoking’s impact on sleep, and here is what they found.*

Smoking Delays Sleep Onset

Smokers in both studies took longer to fall asleep than nonsmokers. The Baltimore study included 6,400 participants enrolled in the Sleep Heart Health Study. On average, the smokers took over 5 minutes longer than the nonsmokers to fall asleep. In the Freiburg study, comprising 88 participants, the smokers took about 25 minutes to fall asleep while the nonsmokers fell asleep in 16 minutes.

Smoking Shortens Sleep Time

Smokers in both studies had shorter nights. Smokers in the Baltimore study slept 14 minutes less than nonsmokers, on average. Smokers in the Freiburg study slept about 11 minutes less than nonsmoking controls.

Smoking Is Associated with Less Deep Sleep

Smokers in the Baltimore study did not sleep as deeply as nonsmokers. Smokers got about 14 percent less deep sleep, and had 24 percent more stage 1 sleep (the lightest sleep stage), than nonsmokers. This shift toward lighter sleep is consistent with data from previous studies, showing that compared with people who have never smoked, smokers tend to (1) report their sleep is less restorative, (2) have more trouble waking up in the morning, and (3) feel sleepier in the daytime.

Smoking Is Linked to Abnormal Breathing & Leg Movement

People diagnosed with sleep apnea or restless legs syndrome were excluded from the Freiburg study. Even so, compared with nonsmokers, smokers in the study had more abnormal breathing as they slept. They also experienced more leg movements. Their sleep was more fragmented due to wake-ups caused by the leg movements. And they reported feeling less refreshed in the morning.

Here’s the Bottom Line

Most of these changes have also been noted in people wearing nicotine patches, so nicotine is likely responsible for at least some aspects of the compromised sleep that smokers have. And nicotine is clearly the prime suspect here: in the brain, it affects production of many of the same neurotransmitters that play a key role in sleep–wake regulation. E-cigarettes contain nicotine as well.

The long-term consequences of smoking are serious, and if the prospect of cancer, emphysema, and heart disease isn’t real enough to make you think twice about continuing, then the harm that smoking causes to your sleep may not be, either. But if you smoke and wonder why you’ve got insomnia, the nicotine might be to blame.

*All findings reported in this blog post were significant.

Insomnia, Memory, and Dreams

Ask insomnia sufferers what they want, and the first thing on their wish lists is “more sleep.” Or “more deep sleep”—the kind associated with feelings of rest and restoration.

I’ll go along with that. But my wish list contains a few more items.

Insomnia may impair memory, and remembering events and dreams may depend on theta activity in the brainAsk insomnia sufferers what they want, and the first thing on their wish lists is “more sleep.” Or “more deep sleep”—the kind associated with feelings of rest and restoration.

I’ll go along with that. But my wish list contains a few more items:

 

 

  1. A better memory for past events is one. My husband narrates whole sequences of his childhood as though he were reliving them again. My memories are skeletal by comparison.
  2. I’d also like to remember my dreams. My husband recalls entire movies that take place nightly in his head, but I’m lucky if I remember a snippet of a dream once in 3 weeks.

Research suggests that insomnia may have negative effects on memory, and also that the consolidation of memories for facts and events takes place largely during deep sleep, when slow brain waves predominate. Now a team of Italian researchers is claiming in a review paper that theta waves—which are slightly faster—are likewise important in the formation and recall of memories, for both waking events and dreams.

Types of Brain Waves

Day and night, neurons are firing in the brain at a mix of frequencies. When we’re alert, most neuronal activity taking place is fast, or high frequency. (Frequency is measured in cycles per second, or Hertz [Hz]). At night the brain slows down. But activity picks up again during rapid eye movement (REM) sleep. Here are the 5 types of brain activity:

  • Gamma waves, 40 to 100 Hz. Associated with intensely focused attention and effortful problem solving.
  • Beta waves, 15 to 40 Hz. Associated with a more relaxed but focused level of attention, thinking, and sensory processing.
  • Alpha waves, 8 to 14 Hz. Associated with resting, relaxation, and meditation. Also the starting point for falling asleep.
  • Theta waves, 4 to 7 Hz. Predominant during Stage 2 sleep. May also occur during very relaxed periods of wakefulness, when the mind is wandering.
  • Delta waves, 0.5 to 3.5 Hz. Predominant during deep sleep.

The mixed-frequency brain activity that occurs during REM sleep—theta, alpha, and beta—makes it look like the brain is more awake than asleep.

Theta Waves Involved in Waking Memory

Research shows that memory processing is characterized by specific waveforms occurring in memory-related areas of the brain. In particular, the Italian researchers write, the theta rhythm “seems to correlate consistently with episodic memory, . . . the ability to remember past experiences and autobiographical events.”

Memory processing involves both inner and outer areas of the brain, and EEG recordings of subjects performing cognitive tasks have shown that theta power increases in key areas during the encoding and retrieval of information. In two studies, participants were exposed to a series of words and then asked to recall them later. The authors found that (1) theta power increased only during the encoding of the items that participants were later able to recall, and (2) the amount of theta power during the encoding phase differentiated good and bad performers when it came time to recall what they learned.

Other studies have shown that theta activity increases during the retrieval of previously learned material. Still other studies have shown that a brain oscillating in theta mode before exposure to new information is primed to recall that information later on.

Theta Involvement in the Recall of Dreams

Some studies of dream recall, in which participants’ brain waves are recorded as they sleep and they’re awakened periodically and asked to report their dreams, suggest a relationship between dream recall and alpha waves. But the findings in these studies overall are inconsistent–possibly because of different study protocols.

More recent research shows that successful dream recall is associated with both alpha and theta activity in frontal areas of the brain. And, as neuroimaging studies suggest that the mechanisms underlying mental processes are similar during wakefulness and sleep, the researchers propose that it’s the relative presence or absence of theta waves that determines whether or not we remember waking events and dreams.

I don’t know if my shoddy memory is related to a deficit of theta power, or what that may or may not have to do with my predisposition to insomnia. But as long as I’m making a wish list, I’d like a better memory. In addition to more deep sleep, I think I’ll ask for more theta power, too.

Do Sleep Spindles Play a Role in Insomnia?

Looking for an objective test of insomnia?

New research suggests there’s a relationship between insomnia and sleep spindles—sudden bursts of fast electrical activity that occur in the brain mostly during stage 2 sleep. Investigators at Concordia University in Montreal found that students with lower spindle activity reported more stress-related sleep problems than students whose spindle activity was high.

objective insomnia marker | fewer sleep spindles in EEGLooking for an objective test of insomnia? Unfortunately, no such test exists.

But scientists hunting for biomarkers of the disorder have noted subtle differences between insomniacs and normal sleepers in the electrical activity occurring in the brain at night. Some studies show that insomniacs spend less time in deep sleep; others show that insomniacs who awaken frequently at night get less REM sleep. Still others show that insomniacs are more prone to high-frequency brain waves during sleep.

New research suggests there’s also a relationship between insomnia and sleep spindles—sudden bursts of fast electrical activity that occur in the brain mostly during stage 2 sleep. Investigators at Concordia University in Montreal found that students with lower spindle activity reported more stress-related sleep problems than students whose spindle activity was high.

Importance of Sleep Spindles

Here's what sleep spindles look like.
Here’s what sleep spindles look like.

Sleep spindles occur throughout the night during periods of non-REM sleep, and more spindles occur in some people than in others. Yet in any individual, spindle density is quite stable from night to night come rain or shine. So spindle density is regarded as an individual trait.

Previous research has shown that sleep spindles protect us from being awakened by noise in the environment. So these short bursts of electrical activity contribute to sleep stability. Spindles have also been found to assist in the overnight retention of memories and enhance learning. Sleep spindle density also correlates with higher scores on tests of intelligence. In short, sleep spindles are highly beneficial.

Concordia Study

Thien Thanh Dang-Vu and colleagues enrolled 12 healthy, normal-sleeping Concordia University students to test their hypothesis that students with fewer spindles would have more trouble sleeping during periods of academic stress. They gathered baseline data from each student at the beginning of a winter semester, when stress levels were low. Students underwent polysomnography (an overnight sleep study) and a battery of pencil-and-paper tests assessing their sleep, stress levels, and mood. Then, during a high-stress period—the week prior to final exams—the students underwent a second round of testing to find out how the stress of exam week was affecting their sleep.

As expected, the lower the sleep spindle activity, the more likely a student was to report sleep problems. In particular, lower spindle density at the beginning of the night—as students were falling asleep—correlated with more sleep complaints in response to academic stress.

Implications

What this implies, the researchers say, is that alongside other factors that predispose us to insomnia—a family history of insomnia, depression or anxiety, hyperarousal, poor health, and pain—people whose brains generate fewer sleep spindles at night are more prone to develop insomnia than those whose spindling activity is high.

Why some people are champion spindlers and others are not is a question that still needs sorting out. But insomnia treatments that promote sleep spindles could only be a good thing. Whether in the form of medication or herbs or pre-sleep activities, I say, bring ’em on!