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Sleep Regularity featured article

Most people understand the importance of sleep duration, but there's another critical—and often overlooked—factor that plays a major role in health and performance: sleep regularity. It's not just about how much sleep you get, but how consistently you go to bed and wake up each day.

A growing body of research suggests that erratic sleep schedules—fluctuating bedtimes, wake-up times, and inconsistent sleep durations—can have profound consequences for both physical and mental health.

Irregular sleep patterns have been linked to everything from metabolic dysfunction and cardiovascular disease to mood disturbances, increased risk-taking behaviors, and even cognitive decline. Studies indicate that maintaining a consistent sleep schedule may be just as important as getting enough sleep, if not more. One particularly striking finding is that sleep variability—especially inconsistent wake times—can predict negative health outcomes more strongly than total sleep duration. **People...

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Episodes

exercise

Dr. Andy Galpin: The Optimal Diet, Supplement, & Recovery Protocol for Peak Performance

Posted on April 22nd 2025 (about 2 months)

Dr. Andy Galpin & Dr. Rhonda Patrick discuss nutrition, supplement, and recovery strategies for improving exercise performance.

sleep

This What Losing Just 1 Hour of Sleep for 3 Nights Does to Your Body

Posted on January 21st 2025 (5 months)

In this clip, Dr. Rhonda Patrick explores the effects of sleep deprivation on insulin signaling, diabetes risk, appetite regulation, and metabolic health.

sleep

Don't Get Much Sleep? Here's the #1 Thing You Should Do

Posted on January 20th 2025 (5 months)

In this clip, Dr. Rhonda Patrick discusses how HIIT improves metabolic health and reduces risks associated with sleep restriction.

Topic Pages

  • Melatonin

    Nocturnally secreted melatonin binds MT1/MT2 receptors in the suprachiasmatic nucleus, dampening neural activity and initiating sleep.

  • Sleep Regularity

    Consistent sleep-wake timing entrains circadian rhythms, aligning homeostatic sleep pressure with circadian sleep propensity, thereby improving sleep consolidation.

  • Time-restricted eating

    Time-restricted eating aligns metabolic cues with circadian clocks, strengthening melatonin rhythms and thereby improving sleep quality.

News & Publications

  • The air in children's sleeping areas harbors high chemical pollutant levels, potentially increasing young children's exposure to toxic compounds. pubs.acs.org
    Sleep Development Pollution

    The air around a child’s bed may carry more chemical pollutants than the bedroom itself. A recent study suggests sleeping spaces are a key source of toxic exposure for young children.

    Researchers collected air samples from the sleeping areas and bedrooms of 25 children between 6 months and 4 years old living in Canada. They also tested the children’s mattresses for chemical emissions, looking for three types of compounds: phthalates (used to soften plastics), flame retardants, and UV filters (used in dyes and textiles). These chemicals belong to a group called semivolatile organic compounds, or SVOCs, which can escape from products and linger in air, dust, and on surfaces.

    The researchers detected nearly 30 different chemicals in each of the three sampling locations—bedroom air, sleeping area air, and mattresses. The air in the sleeping area had higher chemical levels than the surrounding bedroom, confirming that bedding and other nearby items were likely contributing to children’s exposure. In many cases, the mattresses themselves released higher amounts of certain phthalates and flame retardants, while bedding appeared to be a major source of flame retardants.

    These findings suggest that young children face increased chemical exposure while they sleep, a substantial concern given how much time they spend in their sleeping environments. The investigators proposed that parents reduce exposure by regularly washing bedding and sleepwear, as fabrics tend to trap airborne chemicals. Furthermore, some textiles can also release chemicals, so having fewer items in the bed is beneficial.

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  • Resistance training notably improves sleep quality in older adults, outperforming both aerobic and combined exercises. fmch.bmj.com
    Exercise Aging Sleep

    As people age, sleeping problems become more common, often affecting mood, memory, and overall health. A recent study found that resistance training improves sleep in older adults better than other forms of exercise.

    Researchers analyzed 25 clinical trials involving more than 2,100 people to see how different kinds of physical activity influenced sleep quality. They looked specifically at the Pittsburgh Sleep Quality Index, a subjective measure of a person’s sleep quality. The studies compared people who exercised to those who adhered to their usual routines, received health education, or did no physical activity at all.

    Strength training was the most effective approach for improving sleep scores, followed by aerobic activity and then a combination of both. People who engaged in strength exercises were more likely to report better sleep, with the strongest improvement observed across all comparisons. Aerobic activity also helped but wasn’t as effective, and combined exercise had a more modest benefit.

    These findings suggest that resistance training does more than build muscle—it also improves sleep. Resistance training builds bone, too, a critical component of aging well. Learn more in this clip featuring Dr. Brad Schoenfeld.

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  • Sleep disruption reduces the newly discovered hormone 'raptin,' potentially increasing appetite and promoting weight gain. www.nature.com
    Diet Obesity Sleep Hormones

    Sleepless nights don’t just leave you tired—they may also interfere with your body’s ability to regulate hunger. Researchers have long known that poor sleep increases the risk of obesity, but the biological link has remained elusive. A recent study found that a sleep-triggered hormone called raptin helps control appetite and may explain why people who don’t get enough sleep are more likely to gain weight.

    Researchers examined brain activity, hormone levels, and eating behavior under different sleep conditions in mice and humans. They identified a previously unknown hormone, which they named raptin, and tracked where and when it was released. They also studied the effects of a genetic variant that blocks raptin production and examined hormone levels in people with sleep deficiency, obesity, and nighttime eating syndrome.

    They discovered that raptin is produced in a part of the brain that regulates hunger and hormone secretion and is released during sleep. When sleep is disrupted, raptin levels drop. In lab experiments, raptin acted on specific receptors in the brain and stomach to reduce appetite and slow stomach emptying. People with obesity and sleep deficiency had lower levels of raptin, while those who underwent therapy to improve sleep showed increases in the hormone. A genetic variant that blocks raptin production was linked to night-time overeating and obesity.

    These findings indicate that raptin explains how sleep influences weight gain and appetite. Learn more about the effects of sleep deprivation in Aliquot #27: Health consequences of sleep deprivation, part I: Metabolic & immune health and Aliquot #28: Health consequences of sleep deprivation, Part 2: Mental & cognitive health

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  • Melatonin supplementation may heighten DNA repair in night shift workers during daytime sleep, potentially reducing cancer risk. oem.bmj.com
    Cancer Sleep DNA Damage Circadian Rhythm Melatonin Supplements

    Working night shifts may increase the risk of cancer by disrupting the production of melatonin, a hormone essential for DNA repair. This disruption can impair the body’s ability to repair oxidative DNA damage, potentially contributing to cancer development. A recent study found that melatonin supplementation could improve the repair of oxidative DNA damage in night shift workers.

    The researchers conducted a four-week randomized, placebo-controlled trial with 40 night shift workers, providing them a 3-milligram dose of melatonin before their daytime sleep periods. They collected urine samples during daytime sleep and nighttime work periods, measuring 8-hydroxy-2′-deoxyguanosine (8-OH-dG), a marker of DNA repair capacity.

    They found that melatonin supplementation nearly doubled 8-OH-dG excretion during daytime sleep, indicating improved DNA repair. However, they observed no difference in 8-OH-dG excretion during the night shift. Although the melatonin group experienced a slight decrease in wakefulness after falling asleep, the researchers found no differences in total sleep duration or sleepiness levels between the two groups.

    The findings from this small study suggest that melatonin supplementation enhances oxidative DNA repair in night shift workers, offering the potential for reducing cancer risk. More extensive studies may identify optimal dosages and the long-term effects of melatonin supplementation in this population. Learn about the pros and cons of melatonin supplementation in this clip featuring Dr. Satchin Panda.

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  • Misaligned sleep patterns and natural sleep preferences increase mental health risk, hinting at the crucial role of sleep timing and chronotype consistency for healthy aging. www.sciencedirect.com
    Sleep Depression Mental Health Anxiety

    The timing of when a person sleeps—not just how long—plays a vital role in mental health, influencing mood, cognitive function, and overall well-being. A recent study found that misalignment between bedtime and natural sleep preferences can increase the risk of mental health disorders like depression and anxiety.

    Researchers identified the chronotype—whether they were morning or evening types—of nearly 74,000 middle-aged and older adults enrolled in the UK Biobank. They tracked sleep patterns using accelerometry and evaluated their sleep and chronotype alignment. They assessed mental health outcomes through standard diagnostic codes.

    They found that morning types who went to bed late had a greater risk of mental health disorders, including depression and anxiety, than those whose sleep timing matched their chronotype. Interestingly, evening types who went to bed early had a lower risk of depression and a trend toward reduced risks of other mental health issues.

    These findings suggest a mismatch between one’s biological preferences and sleep schedule can harm mental well-being. The investigators posited that people should aim to sleep before 1 a.m. for optimal mental health, even if their natural chronotype favors later sleep. Learn more about chronotypes in this clip featuring Dr. Matthew Walker.

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  • Sleep enhances the brain's waste removal through synchronized fluctuations in norepinephrine and blood volume, a process disrupted by the common sleep aid, zolpidem. https://www.cell.com/cell/abstract/S0092-8674\(24\)01343-6
    Brain Sleep Norepinephrine Neurodegeneration

    The brain doesn’t just rest during sleep—it actively clears out waste that can damage brain cells. This crucial process, known as glymphatic clearance, relies on the movement of cerebrospinal fluid to wash away harmful proteins linked to neurodegenerative diseases. A recent study found that synchronized fluctuations in norepinephrine, blood volume, and cerebrospinal fluid are key drivers of glymphatic clearance during deep sleep, but some popular sleeping pills disrupt this process.

    The researchers tracked blood and cerebrospinal fluid dynamics while mice slept naturally. Then, they examined how zolpidem, commonly known as Ambien, affected these dynamics during sleep.

    They found that norepinephrine fluctuations triggered by the brain’s locus coeruleus drove rhythmic changes in blood vessel size. This facilitated the movement of cerebrospinal fluid into the brain and the removal of waste products. However, zolpidem disrupted norepinephrine activity, reducing cerebrospinal fluid flow and hindering this waste removal process.

    These findings suggest that the brain’s waste removal system relies on a delicate balance of norepinephrine and blood vessel activity. Sleep aids like zolpidem disrupt this process, potentially contributing to neurodegenerative diseases like Alzheimer’s. Learn more about the effects of sleep aids like Ambien in this episode featuring Dr. Matthew Walker.

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  • Workplace design plays a crucial role in sleep health, with sedentary jobs and nontraditional schedules leading to poor sleep patterns, such as regular insomnia or compensatory 'catch-up' sleep. psycnet.apa.org
    Sleep Circadian Rhythm

    Modern workplace changes driven by technology are transforming not only how we work but also how well we sleep. Longer hours spent at desks, increasing reliance on computers, and nontraditional work schedules may undermine sleep health. A recent study found that modern job designs are linked to distinct sleep challenges among full-time workers.

    Researchers analyzed data from nearly 1,300 adults in the Midlife in the United States study, collected at two points over a decade. They examined six sleep health dimensions, including duration, insomnia symptoms, and daytime tiredness. Then, they identified three sleep health profiles: good sleepers (who had few sleep issues), catch-up sleepers (who relied on naps and non-workday sleep to offset shorter workday sleep), and insomnia sleepers (who experienced short sleep, frequent insomnia symptoms, and daytime tiredness).

    They found that only about half of the participants were good sleepers. Participants with sedentary jobs were more likely to be classified as insomnia sleepers. At the same time, those with nontraditional schedules often exhibited a catch-up sleeper pattern characterized by irregular sleep and regular napping. Good sleepers were less likely to be in these roles, suggesting that workplace design powerfully shapes long-term sleep health.

    These findings suggest that job design has marked effects on sleep quality. Reducing sedentary time and stabilizing work schedules could help workers achieve healthier sleep patterns, ultimately improving well-being and overall health. Learn how shift work and other aspects of modern lifestyles influence sleep and health by altering circadian rhythms in this clip featuring Dr. Satchin Panda.

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  • Whole-body cryotherapy improves mood, reduces anxiety, and enhances sleep quality, with specific enhancement in slow-wave, restorative sleep seen in a recent study. www.sciencedirect.com
    Sleep Mental Health Cold Stress

    Cold exposure offers surprising health benefits, and emerging evidence suggests that whole-body cryotherapy enhances wellness and even improves sleep. A recent study found that five days of daily cryotherapy improved mood, reduced anxiety, and enhanced sleep quality in healthy young adults.

    The study involved 20 physically active young adults who underwent five consecutive days of cryotherapy sessions and five consecutive days of no cold exposure. The cryotherapy sessions lasted five minutes in a chamber cooled to -90°C (-130°F). Researchers used actimetry, brain activity recordings, and self-reported questionnaires to measure the participants' sleep patterns. They also assessed their mood, anxiety, and heart rate variability during the nights following each condition.

    Participants who underwent cryotherapy reported a 9% improvement in subjective sleep quality, with women benefiting the most. The cryotherapy sessions also increased slow-wave sleep, the most restorative sleep phase, by an average of seven minutes per night. No substantial changes were observed in heart rate variability or other sleep parameters.

    These findings from this small study suggest that repeated whole-body cryotherapy is a promising strategy for improving slow-wave sleep and psychological well-being, especially for women. Learn more about cold exposure in our comprehensive overview article.

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  • A daily cup of coffee could reduce your risk of heart disease and diabetes by half. academic.oup.com
    Sleep Heart Disease Diabetes Biomarkers Coffee Green Tea Caffeine Stroke Cardiovascular

    Drinking your daily cup of coffee or tea might do more than give you a boost—it could lower your risk of developing multiple serious cardiometabolic conditions simultaneously, like diabetes, heart disease, or stroke. A recent study found that moderate coffee or caffeine consumption may cut your risk of cardiometabolic multimorbidity by as much as 50%.

    Researchers analyzed data from more than 172,000 participants enrolled in the UK Biobank who had no cardiometabolic diseases at the start. Participants reported their coffee, tea, and caffeine consumption; about half provided blood samples for metabolic marker analysis.

    They found that people who drank about three cups of coffee daily (or consumed 200 to 300 milligrams of caffeine daily) were 40% to 50% less likely to develop multiple cardiometabolic diseases than those who drank little or no caffeine. They also discovered that specific blood markers, such as certain lipid components, were linked to coffee and caffeine consumption and a lower risk of cardiometabolic conditions.

    These findings suggest that moderate coffee or caffeine intake reduces the risk of developing cardiometabolic diseases but also slows their progression if they occur. Other evidence points to the many health benefits associated with coffee and caffeine, but it’s crucial to remember their effects on sleep. Learn more in this Aliquot featuring Drs. Guido Kroemer, Satchin Panda, Elissa Epel, Matthew Walker, and Rhonda Patrick

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  • Increasing activity levels improves sleep quality in women. neurosciencenews.com
    Exercise Sleep

    A new study shows that replacing sedentary time with physical activity improves sleep in women. Women who swapped just one hour of sedentary time or low-intensity activity with moderate- or vigorous-intensity activity slept better and felt more rested.

    Researchers investigated the effects of replacing sedentary time with physical activity. The study involved 683 men and women between the ages of 40 and 64 years. The participants wore accelerometers to gauge their activity levels for one week and reported their sleep quality.

    The researchers found that sleep measures improved when women replaced sedentary behavior or low-intensity physical activity with moderate- to vigorous-intensity physical activity. Interestingly, they found no associations between altering men’s activity levels and sleep quality, highlighting the sex-related differences in response to exercise.

    These findings indicate that engaging in moderate- to vigorous-intensity physical activity improves sleep quality in middle-aged women. They also align with other studies that show that exercise improves sleep. Sleep is essential for human health. Learn more about the benefits of sleep in this episode featuring Dr. Matthew Walker.

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  • Obstructive sleep apnea may have a suppressive effect on serum testosterone levels in men, independent of BMI and age. (2021) onlinelibrary.wiley.com
    Obesity Sleep Hormones Testosterone

    Sleep apnea increases the risk of low testosterone.

    Men with sleep apnea are more likely to have low testosterone levels, according to a 2021 study. Men with severe apnea are at the greatest risk of low testosterone.

    Researchers reviewed the findings of 18 studies involving more than 1,800 men that examined links between sleep apnea and male testosterone levels. Then they analyzed a subset of the studies after matching the men’s age, body mass index, and severity of their sleep apnea.

    They found that the men with sleep apnea were more likely to have low testosterone levels, even after considering their age and body mass index. However, the subset analysis revealed that this relationship was only notable for those with severe apnea.

    Sleep apnea is a common, but serious, sleep disorder characterized by brief moments of paused or shallow breathing. People with sleep apnea are at greater risk of high blood pressure, stroke, abnormal heart rhythms, heart failure, diabetes, weight gain, and heart attacks.

    This review identifies links between sleep apnea and testosterone levels. It also underscores the importance of diagnosing and treating sleep apnea, particularly among men whose apnea is more severe.

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  • Even moderate light exposure during sleep harms heart health and increases insulin resistance www.sciencedaily.com
    Sleep Insulin Resistance

    A single night of light exposure during sleep impairs glucose metabolism via activation of the “fight-or-flight” response.

    Light is the primary signal that entrains the body’s master clock to set its 24-hour circadian cycle. Consequently, the body is synchronized to external light-dark cycles. In recent decades, exposure to light from artificial sources has increased, especially during the evening and nighttime hours, with negative effects on human health. Findings from a recent study suggest that a single night of light exposure impairs glucose metabolism via activation of the sympathetic nervous system.

    The sympathetic nervous system is a division of the autonomic nervous system. It responds to both endogenous and exogenous stressors and is widely referred to as the coordinator of the body’s “fight-or-flight” response. The outcome of sympathetic nervous system activation is an increase in heart rate, cardiac output, and blood glucose levels, as well as other physiological responses that prepare the body for action. Evidence suggests that increased sympathetic nervous system activity alters sympathovagal balance (the balance between the sympathetic and parasympathetic nervous systems), driving poor heart rate variability.

    The investigators recruited 20 healthy adults (average age, 26 years) who did not have sleep disorders. Participants spent two nights in a sleep laboratory, where they ate all their meals and went to bed at their habitual times. Half of the participants spent one night in dim light conditions (less than 3 lux, very dark) and one night in room light conditions (100 lux, from four 60-watt incandescent bulbs). The other half spent both nights in the dim light conditions. Participants provided blood samples and underwent oral glucose tolerance tests each morning.

    The investigators found that participants who were exposed to room light conditions during sleep had increased nighttime heart rate, decreased heart rate variability, and increased morning insulin resistance, compared to when they slept in a dark room. They also spent less time in deep, slow-wave sleep.

    These findings suggest that a single night of exposure to room light during sleep impairs glucose metabolism via activation of the sympathetic nervous system. Learn how light from devices impairs sleep in this clip featuring sleep expert Dr. Matthew Walker.

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  • People Who Sleep Less Than Seven Hours Show Lower Intakes of Micro- and Macronutrients www.sci-news.com
    Nutrition Sleep

    People who don’t get enough macro- or micronutrients or fiber have poor sleep.

    Macronutrients (carbohydrates, fats, and proteins), micronutrients (vitamins and minerals), and fiber are the core components of the diet. Inadequate intake of these nutrients can impair biological processes and cause both acute and chronic health problems. Findings from a 2019 study suggest that people who don’t get enough macro- or micronutrients or fiber have poor sleep.

    Sleep is essential for human health. Not getting enough sleep or having poor, fragmented sleep increases a person’s risk of developing many chronic illnesses, including cardiovascular disease, hypertension, diabetes, stroke, obesity, and depression. Evidence suggests that insufficient sleep increases a person’s risk of developing Alzheimer’s disease and dementia. The investigators analyzed data collected in the National Health and Nutrition Examination Survey, an ongoing study of the health and nutritional status of people living in the United States. Their analysis included adults who provided information about their dietary intake, sleep patterns, and overall health.

    They found that roughly one-third of the participants reported short sleep (regularly sleeping less than seven hours per night) and nearly one-half reported having poor sleep quality. Those who had short sleep or poor sleep quality were more likely to have a lower intake of several macro- and micronutrients, including magnesium, niacin, zinc, vitamins A, K, B1, B6, and B12, calcium, and dietary fiber. Although the effects were stronger in women, dietary supplements compensated for the low dietary intake.

    These findings suggest that low intake of macro- and micronutrients impairs sleep in adults and suggest that dietary supplements can compensate for dietary shortcomings. Learn about other dietary components that influence sleep duration and quality in this clip featuring Dr. Matthew Walker.

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  • Children who lack sleep may experience detrimental impact on brain and cognitive development that persists over time www.eurekalert.org
    Brain Sleep

    Children who don’t get enough sleep have altered brain structure and impaired brain function.

    Sleep is essential for normal brain development in children. The American Academy of Pediatrics recommends that children between the ages of six and 12 years sleep nine to 12 hours every night for optimal health, but many children do not meet these recommendations. Findings from a recent study suggest that children who don’t get enough sleep have altered brain structure and impaired brain function.

    The investigators analyzed structural magnetic resonance imaging data and medical records for more than 8,300 children between the ages of nine and ten years who were enrolled in the Adolescent Brain Cognitive Development (ABCD) Study. They also assessed the children’s cognitive performance and mental health status. The parents of the children in the study provided information about their child’s nightly sleep duration. Assessments were repeated when the children reached the ages of 11 to 12 years.

    The study revealed that brain volumes in areas responsible for attention, memory, and inhibition were lower in sleep-deprived children than in those who received adequate sleep. In addition, children who had shorter sleep duration were more likely to experience depression and anxiety and exhibit impulsive behavior and poor cognitive performance. The association between poor sleep and depression persisted at the two-year follow-up.

    These findings underscore the importance of adequate sleep for proper brain function, especially in the developing brain. Learn more about the importance of sleep in this episode featuring Dr. Matthew Walker.

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  • Insomnia, hypertension and smoking, but not high triglyceride levels, are considered possible risk factors for brain aneurysm rupture. www.sciencedaily.com
    Sleep Genetics Tobacco Triglycerides Blood Pressure Aneurysm

    From the article:

    Data from several genome-wide association studies were used to gauge genetic associations to lifestyle and cardiometabolic risk factors. […] According to the analysis:

    -A genetic predisposition for insomnia was associated with a 24% increased risk for intracranial aneurysm and aneurysmal subarachnoid hemorrhage.

    -The risk for intracranial aneurysm was about three times higher for smokers vs. non-smokers.

    -The risk for intracranial aneurysm was almost three times higher for each 10 mm Hg increase in diastolic blood pressure (the bottom number in a blood pressure reading).

    -High triglyceride levels and high BMI did not demonstrate an increased risk for intracranial aneurysm and aneurysmal subarachnoid hemorrhage.

    View full publication

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  • Heightened dream recall ability linked to increased creativity and functional brain connectivity www.psypost.org
    Brain Sleep

    People who frequently recall their dreams tend to be more creative.

    Dreams are a state of consciousness that occurs during sleep. Typically characterized by sensory, cognitive, and emotional experiences, dreams share many similarities with hallucinations. Scientists formerly believed that dreams only occurred during the rapid eye movement, or REM, stage of sleep, but recent research indicates that they can occur at any time during sleep. Findings from a recent study suggest that people who frequently recall their dreams tend to be more creative and exhibit increased functional connectivity in the brain’s default mode network.

    The default mode network is a collection of interconnected neural structures that demonstrate low activity when a person is engaged in a particular task but high activity when not. It also demonstrates activity when a person tries to remember past events or imagine future events. Although some evidence suggests that the default mode network is involved in self-focused, ruminative thought, other evidence suggests it is involved in creativity and spontaneous thought processes.

    The study involved 55 healthy adults (19 to 29 years old) who had normal sleep patterns. Roughly half of the participants reported that they frequently recalled their dreams, recalling about six dreams per week, and the other half reported that they rarely recalled their dreams, recalling fewer than one dream per week. All participants underwent functional magnetic resonance imaging (fMRI) scans while sleeping. Before their scans, they answered questions about their personality, anxiety levels, cognitive ability, and sleep quality. They also completed a battery of tests to gauge memory and creativity.

    They found that both groups of participants had similar personalities, anxiety levels, sleep quality, and cognitive abilities. But participants who frequently recalled their dreams performed better on creativity tests than those who rarely recalled their dreams, suggesting they had greater creative skills. The fMRIs revealed that frequent recallers also exhibited enhanced functional connectivity within the default mode network of their brains than infrequent recallers.

    These findings suggest that high recall of dreams is associated with greater creativity and functional connectivity in the default mode network of the brain, and this connectivity promotes creative thinking during both wakefulness and sleep. Learn more about the roles of dreams in creativity in this clip featuring Dr. Matthew Walker.

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  • Inadequate sleep may preferentially act as a trigger for visceral fat accumulation (randomized controlled crossover study) www.sciencedaily.com
    Diet Obesity Sleep Metabolic Syndrome Visceral Fat

    Inadequate sleep drives abdominal fat gains.

    Visceral fat is body fat that is stored in the abdominal cavity near the liver, pancreas, and intestines. The accumulation of visceral fat is linked to type 2 diabetes, insulin resistance, inflammatory diseases, certain types of cancer, cardiovascular disease, and other obesity-related conditions. Findings from a recent study suggest that not getting enough sleep increases the risk of developing excess visceral fat.

    Sleep is essential for human health. Not getting enough sleep or having poor, fragmented sleep promotes the development of many chronic illnesses, including cardiovascular disease, hypertension, diabetes, stroke, obesity, and depression. Scientists don’t fully understand the mechanisms that drive these effects, but some evidence suggests that disturbances in circadian rhythms play vital roles.

    The trial involved 12 healthy young adults (aged 19 to 39 years) who engaged in an in-patient sleep study. Participants were allowed to have either a full night of sleep (nine hours of sleep opportunity) or restricted sleep (four hours of sleep opportunity) for two weeks. After a three-month washout period, participants repeated the study with the opposite sleep experience. The investigators measured the participants’ caloric intake, energy expenditure, body weight, body composition, and fat distribution throughout the study period.

    They found that when participants were sleep-restricted, they consumed approximately 13 percent more protein and 17 percent more fat (translating to about 300 calories) daily, but their overall energy expenditure did not change. Sleep-restricted participants also gained weight. Much of this weight was in the abdominal area, with a 9 percent increase in total abdominal fat area and an 11 percent increase in visceral fat, compared to when they got a full night’s sleep.

    These findings suggest that insufficient sleep increases caloric intake and promotes weight gain and visceral fat increases. Learn more about the harmful health effects of insufficient sleep in this episode featuring sleep expert Dr. Matt Walker.

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  • Menopause disrupts sleep, accelerating biological aging www.sciencedaily.com
    Aging Sleep Genetics

    Menopause accelerates epigenetic aging.

    Menopause, which typically occurs around the age of 52 years, is the cessation of a female’s menstrual cycle and signifies the loss of reproductive capacity. Evidence suggests that early menopause increases the risk for age-related disease and premature death. Findings from a 2016 study suggest that menopause accelerates epigenetic aging.

    Epigenetics is a biological mechanism that regulates gene expression (how and when certain genes are turned on or off). Diet, lifestyle, and environmental exposures can drive epigenetic changes throughout a person’s lifespan to influence health and disease. Epigenetic age is based on a person’s DNA methylation profile and strongly correlates with their chronological age. However, some exceptions exist. For example, the epigenetic ages of semi-supercentenarians (people who live to be 105 to 109 years old) are markedly younger than their chronological ages.

    The investigators analyzed the DNA methylation profiles of more than 3,100 women enrolled in four large observational studies (Women’s Health Initiative; InCHIANTI; Parkinson’s Disease, Environment, and Genes; and the National Survey of Health and Development) to identify links between epigenetic age and menopause. Their analysis was based on assessment of the biological age of cells taken from the women’s blood, saliva, and inner cheek. Because the age at which a female experiences menopause is heritable, they conducted a Mendelian randomization analysis to identify genetic links between age at menopause and epigenetic aging.

    They found that menopause markedly accelerated epigenetic aging. Females who experienced earlier natural menopause were more likely to have “older” blood than those who experienced later menopause, but females who had surgical menopause (a surgical procedure in which the ovaries are removed) had older blood and saliva than those who experienced natural menopause. Cells taken from the inner cheek of females who took menopausal hormone therapies were younger than those who did not take hormones. They also found that a particular gene variant that influences the age at which a female experiences menopause also influences age acceleration.

    These findings suggest that menopause accelerates epigenetic aging in females. The investigators conceded that their findings do not establish a cause-and-effect relationship, however. In a related study, researchers found that menopause-related sleep disorders, such as insomnia or poor sleep quality, contribute to the accelerated aging associated with menopause. Learn more about accelerated epigenetic aging in this episode featuring Dr. Steve Horvath.

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  • Excess artificial light exposure increases risk of obesity in preschool aged children www.sciencedaily.com
    Obesity Sleep Circadian Rhythm Development Blue Light

    Artificial light exposure increases the risk for obesity among children. Light is the primary signal that entrains the body’s master clock to set its 24-hour circadian cycle. Consequently, the body is synchronized to external light-dark cycles. In recent decades, exposure to light from artificial sources (rather than natural ones) has increased, paralleling the global increases in obesity among adults. Findings from a 2016 study suggest that exposure to artificial light increases the risk for obesity among children.

    Global health experts estimate that more than 42 million children under the age of five years have obesity, roughly one-fourth of whom live in developing nations. Obesity increases a person’s risk for developing chronic diseases such as type 2 diabetes, heart disease, and some cancers. It also imposes considerable financial costs at the individual, healthcare system, and national level.

    The study involved 48 preschool-aged children receiving daycare services in Australia. The investigators measured the children’s baseline body mass index (BMI), sleep duration and timing, light exposure, and physical activity levels via clinical assessment, parent questionnaires, and light and activity trackers. They repeated these measures 12 months later.

    They found that at baseline, children who had longer early exposure to moderate intensity light (such as that from artificial sources) were more likely to have higher BMI, while children who had longer afternoon exposure to bright light (such as that from natural sources) tended to have lower BMI. At the second assessment, the investigators found that even after taking into account sleep duration and timing, BMI, and activity levels, children who had more total light exposure at baseline (due to having earlier exposure) gained more weight than their peers. Specifically, for every hour earlier that the children were exposed to light, they experienced a 0.6 unit increase in BMI. The investigators posited that although this was a small increase, it could be an indicator of a life-long trajectory toward weight gain.

    These findings suggest that greater light exposure, especially when it occurs early in the day from artificial light sources, contributes to weight gain in children. Interestingly, adults that receive early exposure to bright light typically sleep better – a key to maintaining a healthy weight. Learn more in this clip featuring Dr. Matthew Walker.

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  • Brain cells that regulate wakefulness may become overactive with age. www.newscientist.com
    Sleep

    Overactive neurons in the brain contribute to the poor sleep quality that often accompanies aging.

    Sleep is crucial for maintaining cognitive health throughout the lifespan. However, sleep quality often declines with age. Findings from a new study in mice suggest that overactive hypocretin neurons contribute to the poor sleep quality that often accompanies aging.

    Hypocretin, also known as orexin, is a type of neuropeptide – a signaling molecule composed of short amino acids and produced by neurons. Hypocretin is produced primarily in the hypothalamus, where it is involved in aspects of wakefulness and appetite.

    The investigators used optogenetics to study and record the activity of hypocretin-producing neurons in the brains of young and old mice. Optogenetics is a research technique that allows scientists to switch a neuron’s activity on or off using light and genetic engineering.

    They found that older mice had nearly 40 percent fewer hypocretin-producing neurons than younger mice. The remaining neurons, which were more excitable than those present in younger mice, triggered wakefulness and poor sleep. The investigators attributed these changes in the neurons to age-related loss of potassium channels (which regulate neuronal excitability) in the older animals' brains.

    These findings suggest that poor sleep that accompanies aging may be due to intrinsic changes in the number and activity of hypocretin-producing neurons, providing potential targets for sleep therapies in the future. Learn about some of the effects of age-related sleep loss in this episode featuring Dr. Matthew Walker.

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  • Not getting enough sleep increases common cold risk. jamanetwork.com
    Sleep Virus

    Sleep plays roles in many aspects of human health, including immune function. Not getting enough sleep can drive a chronic inflammatory state, increasing a person’s risk for both acute and chronic diseases. Findings from a 2009 study demonstrate that not getting enough sleep increases a person’s risk for developing a common cold.

    The average person experiences two to three colds every year, most of which are caused by rhinoviruses. Working adults in the United States tend to lose nearly nine work hours per cold due to absenteeism and on-the-job productivity losses. Adults caring for a child under the age of 13 years tend to lose at least one hour of work per cold. Together, these productivity losses equate to nearly $25 billion per year.

    The study involved 153 healthy men and women between the ages of 21 and 55 years. Over a period of two weeks, participants kept sleep diaries in which they reported how long they slept each night and how rested they felt upon waking. They also reported their “sleep efficiency,” the ratio of the total time spent asleep versus the total amount of time spent in bed. The study investigators then quarantined the participants and exposed them to RV-39, a type of rhinovirus that causes colds. They monitored the participants for five days to see if they developed cold symptoms.

    The investigators found that participants that had less than seven hours of sleep (on average) were three times more likely to develop a cold than those that had eight or more hours of sleep. Participants with less than 92 percent sleep efficiency were nearly six times more likely to develop a cold than those with 98 percent or higher sleep efficiency.

    These findings suggest that not getting enough sleep or having poor sleep efficiency increases a person’s risk for developing illnesses the common cold. Many people experience difficult falling or staying asleep, increasing their risk for colds and other diseases. Learn how cognitive behavioral therapy benefits people with sleeping problems.

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  • Compounds in herbs and tea improve sleep and daytime functioning. pubmed.ncbi.nlm.nih.gov
    Sleep

    Plant-based dietary compounds exert a wide range of beneficial health effects on humans, likely due to their antioxidant, anti-cancer, and anti-inflammatory properties, among others. Evidence from a recent study suggests that plant-based compounds rosmarinic acid and epigallocatechin gallate (EGCG) improve sleep and daytime function in people with poor sleep.

    Rosmarinic acid is found in many culinary herbs, including rosemary, oregano, sage, thyme, and peppermint. Evidence suggests it influences sleep by regulating neurotransmitters in the brain such as GABA and acetylcholine. EGCG is found in tea. It exerts potent antioxidant, anti-cancer, and anti-proliferative properties. EGCG suppresses neuroendocrine pathways involved in alertness, thus providing anti-anxiety and hypnotic effects.

    Roughly one-third of adults in the United States report having poor or insufficient sleep. Not getting good quality or sufficient sleep increases a person’s risk of developing many chronic illnesses and is associated with mood disturbances, memory impairments, and cognitive dysfunction. Many people who have sleep problems take sleeping pills, which can cause cognitive impairments and daytime sleepiness.

    The intervention study involved 89 healthy adults (average age, 31 years) who reported having poor sleep. Half of the participants took a blend of rosmarinic acid and EGCG (providing at least 65 milligrams of the two combined) in capsule form every night before bed for 30 days, while the other half took a placebo. Participants' caffeine intake and physical activity were not prohibited, but the amount and timing were restricted. The study investigators monitored the participants for changes in sleep (via sleep diary and activity tracker), mood, and neurocognitive functioning.

    The investigators found that participants who took the rosmarinic and EGCG blend experienced better sleep quality and less severe insomnia than those who took the placebo. In addition, those who took the blend did not exhibit any cognitive impairments, but they did demonstrate improvements in daytime attention, working memory, and risk assessment.

    These findings suggest that a blend of rosmarinic acid and EGCG enhances sleep and improves daytime cognitive performance in people with poor sleep. Learn how getting a good night’s sleep reduces your risk of dementia in this video featuring Dr. Rhonda Patrick.

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  • Sleep deprivation mimics symptoms of post-concussion syndrome. news.osu.edu
    Sleep

    A concussion is a type of brain injury that causes temporary loss of brain function. Concussions are common among student athletes and can affect memory, judgment, reflexes, speech, balance, and coordination. Findings from a recent study suggest that sleep deprivation mimics many of the symptoms of post-concussion syndrome.

    Post-concussion syndrome is a condition in which the symptoms of concussion linger far beyond the expected recovery period, lasting months or even years after the original injury. Between 10 and 20 percent of people who experience concussion will have post-concussion syndrome.

    The study was part of the NCAA-U.S. Department of Defense Concussion Assessment, Research, and Education Consortium, an ongoing project investigating the effects of concussion and repetitive head impact. More than 30,000 military cadets and university student athletes provided demographic data as well as information on current and previous sport participation, concussion history, and preexisting personal and medical history.

    They also completed the Sport Concussion Assessment Tool–3rd Edition (SCAT3) symptom evaluation as part of baseline preseason testing. The SCAT3 is a self-reported inventory of 22 symptoms and includes questions about the number of hours of sleep obtained the night before testing.

    The majority of the participants (63 percent of the men and 74 percent of the women) reported having at least one symptom, the most common of which was fatigue or low energy. A subset of the cadets (18 percent of the men and 28 percent of the women) and the university students (11 percent of the men and 20 percent of the women) reported having enough symptoms to meet the diagnostic criteria for post-concussion syndrome. A common denominator among this subset was sleep deprivation (fewer than five hours) the night before the assessment.

    These findings suggest that many of the symptoms people report after a concussion are fairly common among cadets and university athletes who have not sustained a recent injury. They also highlight the need to take sleep and other environmental factors into consideration when determining whether athletes are ready to return to activity.

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  • Antibiotic use disrupts sleep/wake cycles in mice www.sciencedaily.com
    Microbiome Sleep

    Many adults struggle with daytime sleepiness and nighttime insomnia, impairing memory, mood, and focus. Several factors regulate sleep and wake activities, including central and peripheral circadian rhythms and timing of meals. These rhythms also regulate the diurnal activities of the gut microbiota. New research reports that antibiotics, which can alter the gut microbial population, may disrupt normal sleep cycles in mice due to changes in neurotransmitters.

    The human gut is an important site for the production and metabolism of neurotransmitters like serotonin. Neurotransmitters in the gut regulate digestive processes, communicate with the brain directly through the enteric nervous system, and interact with the microbiome. Serotonin is important for regulating sleep/wake cycles, and too little serotonin may decrease sleep quality.

    The scientists gave mice water containing broad spectrum antibiotics for four weeks to deplete their gut microbiota or normal drinking water. They used implantable electrodes to collect detailed sleep pattern data in the mice and measured concentrations of metabolites in the animals' guts and feces.

    The authors reported significant alterations in metabolites related to vitamin, amino acid, and neurotransmitter metabolism in mice whose microbiota had been depleted with antibiotics. These mice exhibited less time in deep sleep during the day (when these nocturnal animals should be sleeping) and more time in deep sleep during the night. They also experienced frequent transitions between rapid eye movement (REM) sleep and non-REM deep sleep, an indicator of decreased sleep quality. The authors suggested this may have been caused by lower levels of serotonin in the gut due to depletion of vitamin B6, a necessary cofactor for producing serotonin.

    This research could have important implications for human health. The authors noted that other research has demonstrated the ability of some prebiotics (fiber and nutrients that are beneficial for the gut microbiota) to improve sleep in humans.

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  • Lack of sleep causes poor emotional control journals.sagepub.com
    Sleep

    Currently selected for this coming member’s digest by team member Melisa B.

    Getting an adequate amount of quality sleep is increasingly recognized as vital for mental and physical health. Sleep deprivation can increase stress hormones associated with anxiety and depression and greater risk of chronic diseases like cardiovascular disease. A recent randomized trial found that a night of sleep deprivation can impair a person’s ability to ignore intrusive thoughts.

    Intrusive thoughts include unpleasant memories, images, or worries that are difficult to ignore or suppress. These types of thoughts can cause low mood and difficulty focusing on important tasks. They are common features of mental illnesses such as major depressive order and post-traumatic stress disorder.

    Poor sleep impairs brain function through a number of mechanisms such as influencing heart rate variability, the variation in time between heart beats. Low heart rate variability indicates greater fight-or-flight response by the autonomic nervous system and is associated with an increased cardiovascular disease risk. Poor sleep is known to decrease heart rate variability.

    The investigators trained a group of 60 participants to associate a set of emotionally negative and neutral scenes with human faces. Then they assigned participants to a night of normal sleep or total sleep deprivation. The next morning participants completed a task called “Think/No Think,” where they were shown a face from the previous day and asked to recall or suppress the scene associated with that face. Their ability to control memory retrieval and suppression was self-reported. The investigators also measured heart rate variability before the task using electrocardiography.

    Participants in the sleep deprivation group reported that they were unable to suppress intrusive thoughts about 50 percent more often than the control group. The authors define intrusive thoughts as memories of scenes from the previous day that the researchers asked participants to suppress during the task. For participants in the well-rested group, higher heart rate variability was predictive of better intrusive thought suppression.

    Normally, the prefrontal cortex controls areas of the brain important emotional regulation, the amygdala, and memory, the hippocampus. The authors suggested the intrusive thoughts experienced by sleep-deprived participants are caused by an increase in fight-or-flight response and subsequent loss of control by the prefrontal cortex, a hypothesis supported by existing literature. They advised that future research should include brain imaging to confirm these results.

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  • Fragmented sleep contributes to increased risk of atherosclerosis. news.berkeley.edu
    Sleep Heart Disease

    Atherosclerosis is a disease of the arteries characterized by the deposition of fatty plaques on the arteries' inner walls. Roughly half of all deaths in developed countries are attributed to atherosclerosis. A new study suggests that a pro-inflammatory pathway triggered by poor sleep contributes to the risk of developing atherosclerosis.

    The study involved more than 1,600 ethnically and racially diverse adults (average age, 68 years) enrolled in the Multi-Ethnic Study of Atherosclerosis. The authors of the study measured the participants' home sleep and activity levels over a period of a week and assessed their brain activity during one night in a sleep laboratory. They also ran blood tests to identify biomarkers associated with disease processes and determined the participants' coronary artery calcification scores, which provide reliable measures of atherosclerosis.

    They found that poor, fragmented sleep led to increased levels of proinflammatory molecules and white blood cells (neutrophils and monocytes). Together, these factors promote inflammation, a key driver in the pathogenesis of not only atherosclerosis but many other diseases as well. Poor sleep also predicted the degree of coronary artery calcification. Their findings held true even after ruling out factors related to age, ethnicity, gender, body mass index, sleep disorders, blood pressure, and smoking.

    These findings underscore the fact that sleep has far-reaching effects on many aspects of health. Learn more in this clip featuring sleep expert Dr. Matthew Walker, in which he describes how the different stages of sleep influence both mental and cardiovascular health.

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  • Chronic sleep deprivation impairs immune function. www.sciencedaily.com
    Sleep

    Sleep deprivation is associated with many chronic health conditions, including Alzheimer’s disease, cardiovascular disease, and type 2 diabetes. Roughly one-third of all adults living in the Unites States are sleep-deprived. A recent study demonstrates that sleep deprivation impairs the body’s immune response, providing a link between inadequate sleep and chronic disease.

    How much sleep a person needs is largely dependent on their chronotype – an individual’s innate tendency to sleep at a particular time during a 24-hour period. Chronotypes are based on circadian rhythms and are genetically determined, making it difficult to identify proper controls for sleep studies.

    To address this problem, this study involved 11 pairs of monozygotic (identical) twins whose self-reported sleep patterns differed by at least 60 minutes per night. The authors of the study monitored the participants' sleep and analyzed their gene expression profiles.

    The average sleep duration for all the study participants was roughly seven hours and 20 minutes per night. The average sleep duration difference among the twin pairs was one hour and four minutes. Gene expression profiles differed between the twins, as well. In particular, poor sleep altered gene expression of factors involved in the immune response of white blood cells. These alterations could contribute to the dysregulated immunity often observed in sleep-deprived people.

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