NICHD highlights some of its ongoing research on sleep
Sleep is more than just an activity that makes people feel rested; it is a complex phenomenon that contributes to cognitive development, general well-being, and biological and behavioral functioning. The NICHD's research has helped improve the understanding of many sleep-related topics, such as circadian rhythms (how the body regulates its sleep-wake patterns and other functions), sleep and intellectual and developmental disabilities (IDDs), and sleep during pregnancy. As families adopt new schedules and routines for school, the Institute focuses on what research tells us about the importance of getting enough sleep and the quality of that sleep.
Research shows (and many parents remind us) that sleep is an important foundation for good health, so anything that negatively affects sleep quantity or quality is of concern. In 2010, the U.S. Department of Health and Human Services (HHS) added new sleep health objectives for the coming decade as part of a 30-year effort to improve health nationwide. Healthy People 2020 sets targets for reaching these public health goals, such as raising awareness of sleep's role in productivity, safety, and quality of life. As part of the initiative, HHS set the following objectives for sleep:
- Raise the percentage of 9th to 12th graders who get enough sleep from 31% to 33%.
- Boost this figure from 70% to 71% for adults.
- Among those with sleep apnea, increase the proportion of people who seek a medical evaluation from 26% to 28%.
- Reduce the number of car crashes caused by drowsy drivers.
In addition to the broader HHS goals, the NICHD Scientific Vision process, which examines scientific priorities for the NICHD and the research community for the next 10 years, identified "understanding sleep disorders" as an area of particular interest, especially among pregnant women and people with IDDs.
The NICHD works with the National Heart, Lung, and Blood Institute and other agencies in supporting the National Center on Sleep Disorders Research. The Center helps coordinate government-supported research, training, and education on sleep and its health effects. On the Center's website, you can find information on sleep disorders, access a sleep curriculum for high school students, and learn more about sleep and your health.
Research, some of it led by the NICHD, continues to advance our understanding of how the body regulates its daily rhythms, how disrupted sleep can be treated in children with autism, how sleep is connected to obesity, how sleep affects pregnancy, and how disrupted sleep affects new parents. Select a link below to learn more about research on these topics:
Controlling the Body's Circadian Rhythms
How the body regulates its biological patterns every 24 hours
The Vital Role of Sleep Across the Lifespan
Sleep is important to people of all ages
Additional Research on Sleep
Sleep-related priorities for NICHD research
Circadian rhythms are the body's regular biological patterns that roughly follow a 24-hour cycle. These rhythms are important for setting sleeping and eating patterns, and they help regulate biological functions, such as metabolism, body temperature, and hormone production. Disruptions to these rhythms, especially for long periods of time, can increase risk for poor health outcomes, including cancer and cardiovascular disease. By understanding circadian rhythms, researchers may be able to create treatments for sleep disorders and reduce associated health problems.
To learn more about circadian rhythms, researchers in the Section on Neuroendocrinology, within the NICHD Division of Intramural Research's Program in Developmental Endocrinology and Genetics, are investigating the pineal gland. This small gland in the brain produces melatonin, a hormone that helps regulate sleeping and waking cycles. As this research expands scientists' understanding of the gland as a factor controlling the body's daily rhythms, it may also help shed light on human conditions related to circadian rhythms, such as hormonal changes, sleep and mood disorders, and problems with alertness.
One project aimed to create an overall picture of differences in the expression of genes in the pineal gland during the day versus the night. Researchers found that during the day, melatonin production is low because of low levels of an enzyme called arylalkylamine N‑acetyltransferase (AANAT). At night, the activity of AANAT increases, resulting in an increase in another compound, called N-acetylserotonin. AANAT is critical to the control of the daily rhythms in the production of melatonin. The increase in melatonin production at night, which leads to drowsiness, has been found in all species that have been examined to date. See the NICHD Division of Intramural Research Annual Report (2011) for more information on this finding.
A 2009 study also showed that the pineal gland may play a role in a broader range of bodily functions than was previously thought. Using a technology that scans the activity of thousands of genes at once, researchers from the Section on Neuroendocrinology and others analyzed rodent pineal glands and found that the activity of 604 genes changed on a 24-hour schedule, more than has been reported to occur in any other tissue. The identified genes are involved in a range of functions, from the cell division cycle to the response of the body's immune system. Approximately 70% of the genes increased their activity at night, while the remaining 30% increased activity during the day. These findings and future studies could help unravel the broader role the pineal gland plays in overall health. For more information on this finding, visit PubMed ID: 19103603.
Earlier work by this group of researchers led to the theory that the pineal gland evolved as an indirect way to improve vision, by keeping toxic compounds away from the eyes. The theory holds that early organisms gradually recognized increases in melatonin as a signal that it was nighttime, and melatonin synchronized their daily cycles. Special light receptor cells developed that were dedicated to producing high levels of melatonin, but the toxic substances needed to make melatonin were harmful to sensitive eye tissue. The theory asserts that these cells then became a structure separate from the eyes—the pineal gland.
Disordered sleep among infants and children is an obvious concern to parents because of disruption to their own sleep schedules. Moreover, patterns of sleep are often overlooked as key influences during development. From newborns to the elderly, sleep plays an intricate role in our lives and forms an important foundation for health, especially in children and adolescents, who are growing mentally and physically.
Research shows that circadian rhythms affect the reproductive processes in a woman's body. In a 2009 study, researchers hypothesized that "clock" genes in a part of the brain called the suprachiasmatic nucleus that help maintain the body's circadian rhythms also control local sensitivity, allowing system-specific processes to be carried out during specific, optimal times of day. To test this theory, researchers examined the changes in the sensitivity of gonadotropin-releasing hormone (GnRH) neurons, GT1-7 cells, to stimulation by two key molecules thought to trigger ovulation, kisspeptin and vasoactive intestinal polypeptide (VIP). GT1-7 cells demonstrated daily changes in protein expression and GnRH secretion in response to stimulation by kisspepetin and VIP. The findings were consistent with the idea that GnRH cells are capable of their own natural circadian cycles, which may be fundamental in coordinating the daily bodily changes in sensitivity to particular signals that impact reproduction. For more information on this finding, visit PubMed ID: 19141986.
In households with newborns, mothers often take on a disproportionate part of nighttime care for the infant. Although breastfeeding frequently dictates nighttime care patterns early on, caretaking roles often persist even after the child stops breastfeeding. Mothers of newborns and young children may experience delayed sleep, interrupted sleep patterns, and early awakenings. As a result, some women reduce their paid work time or experience exhaustion on the job. A recent study supported by the NICHD suggested that these patterns may contribute to gender inequality in earnings and career advancement. (Source: Burgard, S. . The needs of others: Gender and sleep interruptions for caregivers. Social Forces. 89, 1189–1215)
But naptime doesn't just give new parents a chance to get their own rest. Research has revealed that newborn infants are capable of a simple form of learning while they are asleep. Researchers recorded electrical activity in the brain of sleeping infants while video cameras recorded facial expressions. Sleeping infants were exposed to a tone and a faint puff of air on their closed eyelids. In response to the air puff, the infants reflexively squeezed their eyelids tighter. After nine times, only the tone was played, and the process was repeated. After approximately 20 minutes, 24 out of 26 infants would respond to the tone alone, and brain activity measurements revealed changes in brain wave activity, showing that the infants had learned to associate the sound of the tone with the puff of air, even if there wasn't one. This kind of learning is controlled by the cerebellum, a part of the brain often involved in IDDs.
As children grow, sleep continues to play an important role in overall health, especially in the development of brain pathways and processes. Research shows that sleep-disordered breathing (SDB), which is characterized by abnormal breathing patterns during sleep, can affect mental development in infants and children. In 2004, a study funded by the NICHD found that, at 1 year of age, children who had multiple episodes of apnea, a pause in breathing, or slow heart rates during sleep scored lower on tests of mental development than did other children of the same age. For more information on this finding, visit PubMed ID: 15480368.
Sleep continues to affect the human mind and body throughout the aging process. Although the circadian system coordinates internal processes to keep the body healthy, research has shown that with advanced age, the genes that regulate circadian rhythms begin to get disorganized, resulting in disruptions in the sleep-wake cycle and changes in body systems. These circadian disruptions can contribute to the aging process, and chronic disruptions are associated with an increased risk for conditions such as heart disease and diabetes. Gaining more insight into the relationship between aging and the body's internal clocks could lead to a greater understanding of how to maximize good health in later life. For more information on this finding, visit PMCID: 2636858.
People often attribute crankiness or their mood to lack of sleep, and researchers are now making the connection scientifically. One study investigated the impact of sleep deprivation on affect, or mood, in participants across three age ranges: early adolescence, defined as ages 10 to 13; mid-adolescence, defined as ages 13 to 16; and adulthood, defined as ages 30 to 60. Healthy subjects underwent a battery of tests while sleep deprived, and results were compared to those of well-rested controls. The researchers found that adolescents experienced less positive affect when sleep deprived than did adolescents who had gotten a good night's sleep. Sleep deprivation was also found to increase anxiety. Early adolescents rated their most threatening worry as significantly more threatening when they were sleep deprived. Researchers suggested that this skewed threat assessment could be a result of the ongoing development of the pre-frontal cortex in the brain of individuals in this age group. The findings further demonstrate the importance of sufficient sleep for maintaining healthy emotional functioning, especially in adolescents. For more information, visit PMCID: 3163498.
Some changes in affect resulting from disordered sleep are more extreme or persistent, resulting in serious mood disorders. For example, recent studies have linked circadian rhythms to major depressive disorder. Researchers looked at the misalignment between the timing of sleep and the circadian "pacemaker," a cluster of neurons that resides in and influences the activity of the pineal gland. They found that the severity of depression correlated with misaligned circadian rhythms—the greater the sleep delay, the more severe the symptoms of depression. Future studies may be able to look into whether readjusting a patient's circadian rhythms and sleep timing could lead to reduced symptoms and whether this could serve as a treatment for depression. For more on this research, visit PubMed ID: 19524304.
Just as sleep is important in normal development, learning, and wellness, it also plays a unique role in the progression of IDDs, chronic conditions, and other diseases. Sleep disturbances, and particular sleep patterns, can have far-reaching effects on the body, and can also offer opportunities for therapeutic intervention as well as serve as an early indicator for health conditions.
SDB describes a group of disorders characterized by breathing difficulties during sleep. It is a well-recognized symptom of neuromuscular diseases, such as cerebral palsy, Duchene muscular dystrophy, and myasthenia gravis. Left untreated, SDB may contribute to significant cardiovascular disease, neurocognitive deficits, and premature death in those with these conditions. The symptoms of SDB can be subtle and may be present long before signs of respiratory failure emerge. But detecting SDB in patients with neuromuscular diseases can be problematic. Once a diagnosis of SDB has been confirmed, there are multiple approaches and other supportive measures that may be used in treatment, making early detection all the more important. For more information, visit PubMed ID: 20113988.
Adolescents living with chronic pain represent a unique subgroup in need of further investigation. A 2010 study sought to identify differences in sleep behaviors, sleep quality, and prevalence of insomnia symptoms in adolescents with chronic pain compared to healthy peers. Research findings revealed that a significantly higher percentage of chronic pain subjects reported symptoms of insomnia, as well as higher arousal—feeling awake—at bedtime and lower sleep quality overall. Chronic pain and levels of arousal before going to sleep represent significant predictors of insomnia. The researchers theorized that while disruptions in sleep may originally be related to the pain, the symptoms may become a separate sleep disorder over time due to behavioral and psychological factors. By assessing insomnia in adolescents dealing with chronic pain, sleep-specific interventions and behavioral targets may be identified for future treatment development. For more information on this finding, visit PubMed ID: 21030151.
Researchers have also found that, if left untreated, sleep disturbances and sleep disorders, such as insomnia, can carry significant adverse daytime consequences for children and place them at risk for poorer health outcomes. Children with acute and chronic medical conditions are affected more by sleep disturbances than are their healthy peers. These disturbances may be caused by other health conditions occurring at the same time, treatment regimens, hospitalization, or other aspects of disease. Clinical care for these children should emphasize regular sleep assessments and sleep routines, as well as promote healthy sleep habits and health outcomes. For more information on this work, visit PubMed ID: 21600350.
The NICHD also studies sleep's effects on mental and cognitive development. The Institute's IDD Branch supports research on sleep disturbances or altered circadian rhythms as part of the conditions associated with IDDs. Many individuals with chromosomal disorders, such as Down syndrome, or genetic syndromes, such as Fragile X syndrome, Rett syndrome, and Cornelia de Lange syndrome, have problems related to sleep quality and sleep quantity. In addition, many individuals with autism spectrum disorders (ASD), certain seizure disorders, or self-injurious behavior have either sleep apnea or disrupted sleep cycles.
The NICHD supported a recent study examining the use of melatonin to treat sleep-onset insomnia, or difficulty falling asleep, in children with ASD. The study found that supplemental melatonin improved children's sleep and behavior and reduced stress in parents. Research in the field is especially important because little is known about the nature of the sleep disorders or circadian rhythm disruptions that occur with these conditions. Equally as important, the sleep-related effects of these conditions may also affect family members. For more information on this finding, visit PubMed ID: 22160300.
With pediatric obesity on the rise, the NIH is working to understand how sleep and obesity are related, especially among women and teens. The NICHD is taking part in these trans-NIH efforts, and the NICHD's Endocrinology, Nutrition, and Growth (ENG) Branch and other components support research on the relationship between sleep and childhood obesity, specifically the relationship between sleep duration or quality and children's eating habits and physical activity.
Rates of obesity have been steadily increasing, along with disorders commonly associated with obesity, such as cardiovascular disease and type 2 diabetes. At the same time, average sleep times have been decreasing. Recent evidence has suggested that insufficient sleep may stimulate overeating, thus playing a role in the current obesity and diabetes epidemics. In human sleep laboratories, investigators can carefully control sleep behavior and study links between amount of sleep and changes in levels of hormones that are involved in eating behavior, hunger, glucose metabolism, and appetite. Researchers have found that, compared to normal sleep patterns, sleep restriction impairs glucose metabolism and affects the brain, causing it to prefer taking in more food than is necessary. A better understanding of the adverse effects of sleep restriction on the central nervous system's control of hunger and appetite may have important implications for public health. For more information on visit PMCID: 3176603 and PubMed ID: 21659802.
Sleep loss may also contribute to risk for diabetes. To explore this connection, researchers exposed healthy volunteers to experimental sleep loss. The subjects exhibited decreased insulin sensitivity, which resulted in impaired glucose tolerance and, in turn, an increased risk of diabetes. Screening for habitual sleep patterns in patients with diabetes and obesity is, therefore, an important method to consider when working to better understand and treat these conditions. For more information, visit PubMed ID: 21112019.
Extending the time spent sleeping could be explored as a potential behavioral intervention technique to prevent weight gain or aid in weight loss. Avoiding sleep deprivation may help prevent the development of obesity, particularly in children. For more information on this finding, visit PubMed ID: 19955752.
Women and children also represent unique populations for the study of obesity and diabetes. Women with a condition called polycystic ovary syndrome (PCOS), for example, are not only at higher risk for diabetes and cardiovascular disease, but also for obstructive sleep apnea (OSA), a condition in which air flow during breathing is decreased because of obstructed airways during sleep. Researchers have sought to determine whether continuous positive airway pressure (CPAP) as a treatment of OSA has beneficial effects on body functions in those with PCOS. Researchers found that in young obese women with PCOS, successful treatment of OSA has far-reaching benefits such as improving insulin sensitivity and reducing blood pressure. The extent of these beneficial effects is affected by the number of hours of CPAP used and the degree of obesity. For more information on this research, visit PubMed ID: 21123449.
The increasing prevalence of obesity also seems to be associated with an increased prevalence of OSA in children. The mechanisms that may contribute to this association and their interactions are not well studied and the treatment of obese children with OSA is not yet standardized. Methods of treatment include surgical removal of the tonsils and adenoids, oral appliances, positional therapy, and weight loss. Investigators found the interactions between obesity, OSA, and metabolic syndromes to be complex, and OSA seems to be an independent factor that may produce certain metabolic effects, such as insulin sensitivity. For more information on this work, visit PubMed ID: 19875714.
Another NIH effort to enhance sleep research was undertaken by OppNet, which advances basic behavioral and social science research at NIH through coordinated activities and initiatives that build a body of knowledge about the nature of behavior and social systems. In 2010, OppNet issued several sleep-related funding opportunity announcements (FOAs). Applicants were asked to propose projects investigating the reciprocal interactions of the processes of sleep and circadian regulation and function with behavioral and social environment processes. Five grants were funded in 2011 under the two FOAs.
One of these grants was awarded through the NICHD to investigate the effects of divorce on sleep. Divorce is a major life stressor that carries with it an increased morbidity and mortality rate, but little is known about the psychological or behavioral mechanisms that explain these associations. Individuals with disturbed sleep are also at an increased risk for a variety of long-term negative health outcomes, including premature death. Researchers at the University of Arizona are undertaking a study that will explore the potential associations between sleep and divorce-related psychological stress. They will collect data on sleep, social engagement, and other distress measures from 120 recently separated individuals to determine why some individuals have an elevated risk for poor health outcomes over time. The researchers hope the findings will help clarify how the stress of divorce translates into health outcomes. The research may also provide important basic information about the relationships between sleep, social behavior, and psychological stress.
From pregnancy and birth through life-long development, the NICHD research aims to understand sleep's role and effects on health and development.
For more information, select one of the links below:
- NICHD News Releases on Sleep
- National Center on Sleep Disorders Research
- National Institute of General Medical Sciences: Circadian Rhythms Fact Sheet
- National Sleep Foundation Homepage
Originally posted: September 5, 2012