Category: Sleep Disorders

If you want to look attractive and healthy, the best thing you can do is get a good night's sleep, finds research in the Christmas issue published on the British Medical Journal website.

For the first time, say the authors, there is scientific backing for the concept of beauty sleep.

The study, led by John Axelsson from the Karolinska Institutet in Sweden, investigated the relationship between sleep and perceptions of attractiveness and health. The authors believe this research is important in today's 24 hour society with the number of people suffering from sleep disorders and disturbed sleep on the rise.

Twenty-three participants between the ages of 18 to 31 took part in the study. They were photographed between 2pm and 3pm on two occasions, once after normal sleep and once after being deprived of sleep. Smokers were excluded from the research and no alcohol was allowed for two days prior to the experiment.

The photographs were taken in a well-lit room and the distance to the camera was fixed. During both photography sessions participants wore no make-up, had their hair loose (combed back if they had long hair) and underwent similar cleaning or shaving procedures. They were asked to have a relaxed, neutral facial expression for both photos.

Sixty-five observers, who were blinded to the sleep status of the subjects, rated the photographs for attractiveness and whether the individuals looked healthy/unhealthy or tired/not tired.

The observers judged the faces of sleep-deprived participants as less healthy, less attractive and more tired.

The authors conclude that the facial signals of sleep deprived people affect facial appearance and judgments of attractiveness, health and tiredness.

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Journal Reference:

1. John Axelsson, Tina Sundelin, Michael Ingre, Eus J W Van Someren, Andreas Olsson, Mats Lekander. Beauty sleep: experimental study on the perceived health and attractiveness of sleep deprived people. BMJ, 341 DOI: 10.1136/bmj.c6614

In the busy world of a honey bee hive, worker bees need their rest in order to best communicate the location of food to their hive mates, research from The University of Texas at Austin shows.

"When deprived of sleep, humans typically experience a diminished ability to perform a variety of tasks, including communicating as clearly or as precisely," said Dr. Barrett Klein, a former ecology, evolution and behavior graduate student at the university. "We found that sleep-deprived honey bees also experienced communication problems. They advertised the direction to a food site less precisely to their fellow bees."

For humans, imprecise communication can reduce efficiency, cost money, and in some cases, cost lives. For honey bees, Klein says it could affect their success in locating food, which could lead to a less competitive colony.

"While the importance of sleep has been studied in Drosophila flies for several years," said Dr. Ulrich Mueller, professor of biology and study coauthor, "Barrett's study is the first to address the function of sleep in a social insect in the context of its society, and the first to show that sleep deprivation impairs precision of communication in an insect."

The research was published in PNAS Early Edition this week.

There are various ways to poke and prod humans to force them to stay awake prior to measuring the effects of sleep deprivation. But how to make bees in a hive lose sleep?

Klein invented a magnetic machine aptly named the "insominator," a contraption he passed over quietly resting bees during the night to deprive them of sleep. The bees, outfitted with small metallic backpacks, were jostled into activity by magnets in the insominator, and this was repeated over the course of normal sleep time.

Barrett then recorded the behaviors of the sleepless bees and discovered they weren't able to communicate as well the direction of nectar-filled flower patches to their sisters through their usual waggle dance.

"The dance was not necessarily wrong, but it was less precise than dances performed by bees that were not sleep-deprived," says Klein. "We expect that a less precise dance would lead to fewer followers making it to the food source, and we hope to test this in the future."

Klein is a researcher at Universität Würzburg in Germany. His coauthors include Arno Klein from Columbia University, Margaret Wray and Thomas Seeley from Cornell University and Ulrich Mueller at The University of Texas at Austin.

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Journal Reference:

1. B. A. Klein, A. Klein, M. K. Wray, U. G. Mueller, T. D. Seeley. Sleep deprivation impairs precision of waggle dance signaling in honey bees. Proceedings of the National Academy of Sciences, 2010; 107 (52): 22705 DOI: 10.1073/pnas.1009439108

Nearly three-quarters of patients with Parkinson's disease experience fatigue or excessive daytime sleepiness (EDS), but clinicians should assess both problems separately in order to improve the profession's understanding of their distinct, but overlapping, physiology. That is the key finding of a study published in the December issue of the European Journal of Neurology.

Researchers from the University Hospital of Zurich, Switzerland, studied 88 outpatients with Parkinson's. They found that 72% suffered from fatigue or EDS, with just under half of them suffering from both.

"Sleep-wake disturbances such as fatigue and EDS are important non-motor features of Parkinson's" says co-author Dr Christian Baumann. "Their causes remain elusive, but it is possible that multiple factors such as neurodegeneration and medication contribute to them.

"It is important that physicians assess these symptoms, because they have a marked impact on patients' motor functions, everyday activities and quality of life.

"EDS tends to affect up to 50% to 75% of Parkinson's disease patients. This is higher than in other brain disorders such as multiple sclerosis, ischaemic stroke and traumatic brain injury. Fatigue is estimated to affect 40% to 60% of patients with Parkinson's disease, but is often not diagnosed.

"The aim of our study was to systematically assess EDS and fatigue in Parkinson's disease, to determine the overlap between the two symptoms and associate them with other motor and non-motor symptoms and dopaminergic medication."

Eighty-eight consecutive patients aged 38 to 84 attending a movement disorders clinic over a ten-month period were included in the study. Their average age was 67.5 years and 69% were male. Disease duration ranged from two to 28 years, with an average of just under ten years.

Key findings included:

• 72% of patients suffered from fatigue, EDS or a combination of both. 59% reported fatigue, 24% on its own and 35% with EDS. 48% reported EDS, 13% on its own and 35% with fatigue.
• Fatigued patients were almost twice as likely to suffer from EDS than non-fatigued patients (60% versus 31%).
• EDS was more common and severe with longer disease duration, but the same pattern was not observed when it came to fatigue.
• Fatigued patients with Parkinson's disease had more severe motor symptoms than patients without fatigue. They were also more likely to suffer from Parkinson's-related insomnia than patients without fatigue (77% versus 53%), autonomic disturbances (46% versus 19%) and depression (52% versus 28%).
• Insomnia was more prevalent in patients with EDS than without (79% versus 57%) but the researchers found no differences when it came to severity of motor symptoms, hallucinations, autonomic disturbances or depression.
• Increased sleep duration (hypersomnia) was associated with fatigue but not EDS. The 17% of patients who reported increased sleep duration were more likely to be severely affected by motor symptoms than patients with average sleep duration, but did not show an increase in other symptoms.
• Most of the patients (50%) were receiving a combination of levodopa and a dopamine agonist, 38% were just receiving levodopa and 10% were just receiving a dopamine agonist. No patients were on rasagiline or selegiline.
• Dopaminergic treatment exerted a stronger influence on EDS than on fatigue. When dopamine agonists were combined with levodopa, this made EDS even worse.

"Our findings suggest that although fatigue and EDS often co-exist in patients with Parkinson's they are differently associated with severity of motor symptoms, disease duration, depression and dopaminergic treatment" concludes Dr Baumann. "For this reason, we feel that fatigue and EDS should be separately assessed in patients with Parkinson's in order to improve our understanding of their distinct but overlapping physiology."

A study in the Dec. 1 issue of the journal Sleep found that deployment to Iraq and Afghanistan significantly influenced sleep quality and quantity in a population of 41,225 military service personnel. The study suggests that the promotion of healthier sleep patterns may be beneficial for military service members.

Results show that participants who completed a follow-up survey during deployment were 28 percent more likely to report having trouble falling asleep or staying asleep than those who had not yet been deployed; participants who completed follow-up after deployment also were 21 percent more likely to have trouble sleeping.

"This is the first large-scale, population-based study of sleep patterns in the military," said lead author Amber D. Seelig, data analyst for the Department of Deployment Health Research at the Naval Health Research Center in San Diego, Calif. "The primary finding of this study is that deployment does appear to affect sleep patterns in our population."

Participants were more than two times more likely to report trouble sleeping if they had baseline symptoms of mental health problems such as posttraumatic stress disorder or depression, or if they rated their general health as only fair/poor. The deployed and postdeployment groups also reported sleeping significantly less than the nondeployed group; however, the association between deployment status and sleep duration was no longer significant after adjustments for follow-up mental health conditions and combat exposure.

"We identified potential mediators, combat exposures and mental health disorders, for the relationship between deployment and trouble sleeping," said Seelig.

According to the authors, sleep disturbances commonly co-occur with mental health conditions. They speculated that enhancing the quality and increasing the quantity of sleep during and after deployment may be one way to potentially reduce the occurrence of mental health problems in military personnel.

The study involved 41,225 personnel on military rosters who completed a baseline survey between 2001 and 2003 as well as a follow-up survey between 2004 and 2006. The study group represented all Service branches and components of the U.S. military, including active duty and Reserve/National Guard personnel. About 27 percent of participants (n = 11,035) completed the follow-up survey during or after deployment in support of the operations in Iraq and Afghanistan.

The American Forces Press Service reports that troop levels in Iraq peaked at nearly 170,000 in 2007, and fewer than 50,000 troops will remain in Iraq until Dec. 31, 2011, to advise and assist Iraqi security forces. According to NATO, the U.S. currently has 90,000 troops in Afghanistan.

Participants who had trouble sleeping at follow-up indicated that during the past month they had moderate or more severe trouble falling asleep or staying asleep, or that the problem occurred several days or more than half the days. Trouble sleeping was reported by 25 percent of participants who had not deployed, 27.1 percent of those in the postdeployment group, and 30.5 percent of people in the deployment group.

Sleep duration was defined as the number of hours that participants reported sleeping during an average 24-hour period over the past month. Adjusted average sleep time was fairly short, with almost every subgroup reporting that they slept about 6.5 hours. According to the authors, this degree of moderate sleep restriction may have lasting effects on performance that cannot be quickly recovered.

In a separate sub-analysis, the authors also found that the adjusted mean sleep duration for mothers of young children and pregnant women in all three deployment groups was less than six hours. They suggested that the normal stressors of pregnancy and motherhood may be multiplied in military women who face the possibility of future deployment and separation from their families.

"We were surprised to see how little sleep pregnant and postpartum women were getting," said Seelig. "Even when we looked at other literature, it seems that the women in our study were reporting much shorter sleep than civilian pregnant women."

The study was funded by the Military Operational Medicine Research Program, which conducts collaborative research with university and commercial laboratories and other federal agencies oriented toward solving critical problems facing the Army.

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Journal Reference:

1. Seelig AD; Jacobson IG; Smith B; Hooper TI; Boyko EJ; Gackstetter GD; Gehrman P; Macera CA; Smith TC. Sleep patterns before, during, and after deployment to Iraq and Afghanistan. Sleep, 2010; 33 (12): 1615-1622 [link]

 Working mothers are two-and-a-half times as likely as working fathers to interrupt their sleep to take care of others. That is the finding of a University of Michigan study providing the first known nationally representative data documenting substantial gender differences in getting up at night, mainly with babies and small children.

And women are not only more likely to get up at night to care for others, their sleep interruptions last longer — an average of 44 minutes for women, compared to about 30 minutes for men.

"Interrupted sleep is a burden borne disproportionately by women," said sociologist Sarah Burgard, a researcher at the U-M Institute for Social Research (ISR). "And this burden may not only affect the health and well-being of women, but also contribute to continuing gender inequality in earnings and career advancement."

For the study, Burgard analyzed time-diary data from approximately 20,000 working parents from 2003 to 2007, drawn from the U.S. Census Bureau's American Time Use Survey.

The gender gap in sleep interruptions was greatest during the prime childbearing and child-rearing years of the twenties and thirties, she found.

Among dual-career couples with a child under the age of one, 32 percent of women reported sleep interruptions to take care of the baby, compared with just 11 percent of men. The proportion reporting interrupted sleep declined with the age of the child, with 10 percent of working mothers and 2 percent of working fathers with children ages 1 to 2 reporting sleep interruptions, and just 3 percent of working mothers and 1 percent of working fathers with children ages 3 to 5.

"What is really surprising," Burgard said, "is that gender differences in night-time caregiving remain even after adjusting for the employment status, income and education levels of each parent. Among parents of infants who are the sole breadwinner in a couple, for example, 28 percent of women who are the sole breadwinner report getting up at night to take care of their children, compared to just 4 percent of men who are the only earner in the couple."

In related research, Burgard and colleagues found that women get slightly more sleep compared to men. But getting about 15 minutes more total sleep a day may or may not compensate for the greater sleep interruptions women face.

"Women face greater fragmentation and lower quality of sleep at a crucial stage in their careers," Burgard said. "The prime childbearing years are also the time when earnings trajectories are being established, and career advancement opportunities could well be foregone if women reduce their paid work time or see their workplace performance affected because of exhaustion. As a result, sleep interruption may represent an under-recognized 'motherhood penalty' that influences life chances and well-being."

The findings also have implications for public health interventions to improve sleep. "Generally, these interventions target individual behaviors, such as the use of alcohol, caffeine or tobacco," said Burgard. "Or they focus on nightly routines that help people to relax and fall asleep or stay asleep more successfully.

"But for parents of young children, the best approach might be discussions and negotiations about whose turn it is to get up with the baby tonight."

The study, forthcoming in the peer-reviewed journal Social Forces, was funded by the National Institute of Child Health and Human Development, the National Institute on Aging, and the Sloan Foundation.

Young children who get most of their sleep at night perform better in executive functioning than children who don't sleep as much at night, a new study finds. The study of 60 Canadian children aged 1, 1-1/2 and 2, examined the children's sleep habits and executive functioning skills, including impulse control and mental flexibility. The researchers found that children who sleep mostly at night did better on executive function tasks, especially those involving impulse control.

At ages 1 and 1-1/2, children who get most of their sleep at night (as opposed to during the day) do better in a variety of skill areas than children who don't sleep as much at night.

That's the finding of a new longitudinal study conducted by researchers at the University of Montreal and the University of Minnesota. The research appears in the November/December 2010 issue of the journal Child Development.

The study, of 60 Canadian children at ages 1, 1-1/2, and 2, looked at the effects of infants' sleep on executive functioning. Among children, executive functioning includes the ability to control impulses, remember things, and show mental flexibility. Executive functioning develops rapidly between ages 1 and 6, but little is known about why certain children are better than others at acquiring these skills.

"We found that infants' sleep is associated with cognitive functions that depend on brain structures that develop rapidly in the first two years of life," explains Annie Bernier, professor of psychology at the University of Montreal, who led the study. "This may imply that good nighttime sleep in infancy sets in motion a cascade of neural effects that has implications for later executive skills."

When the infants were 1 year old and 1-1/2 years old, their mothers filled out three-day sleep diaries that included hour-by-hour patterns, daytime naps, and nighttime wakings. When the children were 1-1/2 and 2, the researchers measured how the children did on the skills involved with executive functioning.

Children who got most of their sleep during the night did better on the tasks, especially those involving impulse control. The link between sleep and the skills remained, even after the researchers took into consideration such factors as parents' education and income and the children's general cognitive skills. The number of times infants woke at night and the total time spent sleeping were not found to relate to the infants' executive functioning skills.

"These findings add to previous research with school-age children, which has shown that sleep plays a role in the development of higher-order cognitive functions that involve the brain's prefrontal cortex," according to Bernier.

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Journal Reference:

1. Annie Bernier, Stephanie M. Carlson, Stéphanie Bordeleau, Julie Carrier. Relations Between Physiological and Cognitive Regulatory Systems: Infant Sleep Regulation and Subsequent Executive Functioning. Child Development, 2010; 81 (6): 1739 DOI: 10.1111/j.1467-8624.2010.01507.x

A small study of Japanese surgeons suggests that duration of surgery and the amount of blood loss are associated with increased stress scores, and that night duty is associated with reduced stress arousal scores, according to a report posted online that will be published in the March print issue of Archives of Surgery, one of the JAMA/Archives journals.

Young physicians are decreasingly likely to choose surgery as a specialty, according to background information in the article. About 80 percent fewer chose the profession in 2000 compared with the 1980s. "One of the reasons is the unfavorable working conditions experienced by surgeons, which has led to a decrease in the number of surgeons and, in turn, has caused even greater increases in the surgeons' workload and risk of errors," the authors write. "It has therefore become a vicious circle."

The effect of surgical stress on patients has been widely studied, whereas the stress on surgeons due to surgery and night duty has not. Koji Yamaguchi, M.D., Ph.D., and colleagues at University of Occupational and Environmental Health, Kitakyushu, Japan, studied 66 surgeons at one university hospital and 15 community and public hospitals. Both before and after day shifts, operations and night duty shifts, participants completed questionnaires assessing stress and workload and provided urine samples, which were analyzed for levels of a compound (biopyrin) that indicates the body is under stress.

Questionnaires revealed that the surgeons experienced stress following surgery, which increased with the duration of surgery and the amount of surgical blood loss. "There were no significant associations between surgical stress and number of operations per day, number of operations as a surgeon, number of operations as an assistant or laparoscopic or conventional surgery," the authors write.

The average operating time was 210 minutes. Urine analysis showed that biopyrin levels were significantly higher after an operation that was 210 minutes or longer compared with 209 minutes or shorter, and also that these levels increased after an operation in which 200 grams or more of blood was lost.

Surgeons who had night duty got less sleep. Based on urine biopyrin levels, surgeons experienced more stress the morning after night duty. They also demonstrated lower stress arousal scores when they finished the day shift following night duty than they were when finishing a day shift not preceded by night duty.

"The problem of chronic sleep deprivation and overwork of surgical residents has become an important issue in the world, including Japan. A combination of poor-quality daytime sleep and increased sleep pressure during the night may result in lowered levels of alertness and an increased risk of errors in people on night duty, such as medical personnel," the authors write. "The present study demonstrated the stress of night duty on surgeons subjectively and objectively. Surgeons' working conditions, including night duty, should be improved to enhance the quality of life for surgeons, resulting in fewer errors in operations and medical treatments and better medical services for patients."

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Journal Reference:

1. Koji Yamaguchi; Shuichi Kanemitsu; and the Kitakyushu Surgical Study Group. Surgeons' Stress From Surgery and Night Duty: A Multi-institutional Study. Archives of Surgery, 2010; 0 (2010): archsurg. 2010. 250 DOI: 10.1001/archsurg.2010.250

People who sleep poorly or do not get enough sleep have higher levels of inflammation, a risk factor for heart disease and stroke, researchers have found.

Data from a recent study are scheduled presented Nov. 14 at the American Heart Association Scientific Sessions in Chicago by Alanna Morris, MD, a cardiology fellow at Emory University School of Medicine.

The results come from surveying 525 middle-aged people participating in the Morehouse-Emory Partnership to Eliminate Cardiovascular Health Disparities (META-Health) study on their sleep quality and sleep duration. The META-Health study's co-directors are Arshed Quyyumi, MD, professor of medicine at Emory University School of Medicine and director of Emory's Cardiovascular Research Center, and Gary Gibbons, MD, director of the Cardiovascular Research Institute at Morehouse School of Medicine. Donald Bliwise, MD, director of the Emory University Sleep Program, contributed additional guidance.

Acute sleep deprivation leads to an increased production of inflammatory hormones and changes in blood vessel function, but more research is needed on the physiological effects of chronic lack of sleep, Morris says.

"Most of the studies looking at the body's response to lack of sleep have looked at subjects who have been acutely sleep deprived for more than 24 hours in experimental sleep laboratories," she says. "Nothing of this sort has been investigated in epidemiologic studies."

In the META-Health study, the researchers assessed sleep quality using the Pittsburgh Sleep Quality Index survey, where a score over six (based on the median sleep score of the study population) is considered poor. They also analyzed their data based on hours of sleep.

Individuals who reported six or fewer hours of sleep had higher levels of three inflammatory markers: fibrinogen, IL-6 and C-reactive protein. In particular, average C-reactive protein levels were about 25 percent higher (2 milligrams per liter compared to 1.6) in people who reported fewer than six hours of sleep, compared to those reporting between six and nine hours.

That difference was still significant even when the data is corrected for known risk factors such as smoking, blood pressure, diabetes and obesity, Morris says.

C-reactive protein is used extensively as a marker of inflammation and heart disease risk. People whose C-reactive protein levels are in the upper third of the population (above 3 milligrams per liter) have roughly double the risk of a heart attack, compared with people with lower C-reactive protein levels, according to the American Heart Association and Centers for Disease Control and Prevention.

"For people who got little sleep, the C-reactive protein levels were increased, but still in the range of what health authorities would consider low to intermediate risk," she says. "However, our study population represents a community-based population [as opposed to patients in the hospital or with known cardiovascular disease], so they have overall lower risk and lower C-reactive protein levels than many of the high risk populations in other studies."

Inflammation may be one way poor sleep quality increases the risks for heart disease and stroke, Morris says.

"It remains uncertain whether short sleep duration contributes directly to cardiovascular mortality, or whether it is a mediating or moderating factor," she says.

Previous research has shown that people who sleep between seven and eight hours per night live longest, and that especially short or especially long sleep durations bring higher mortality. Researchers find that short and long sleep durations are often seen together with high blood pressure, obesity, diabetes and psychological stress — all risk factors for heart disease and stroke.

Long sleep duration may reflect a compensation for sleep apnea, which the sleep quality survey does not directly address. However, in the META-Health study, people who slept for more than nine hours didn't show significantly higher levels of inflammation markers.

In a separate poster, Morris is also presenting research on a difference between men and women in the interaction between sleep quality and arterial stiffness. Her results show that both men and women with poor sleep quality had higher blood pressures, but only men with poor sleep quality had a higher arterial stiffness, a lack of blood vessel flexibility which drives hypertension and puts more burden on the heart.

As humans, we spend about a third of our lives asleep. So there must be a point to it, right? Scientists have found that sleep helps consolidate memories, fixing them in the brain so we can retrieve them later. Now, new research is showing that sleep also seems to reorganize memories, picking out the emotional details and reconfiguring the memories to help you produce new and creative ideas, according to the authors of an article in Current Directions in Psychological Science.

"Sleep is making memories stronger," says Jessica D. Payne of the University of Notre Dame, who co-wrote the review with Elizabeth A. Kensinger of Boston College. "It also seems to be doing something which I think is so much more interesting, and that is reorganizing and restructuring memories."

Payne and Kensinger study what happens to memories during sleep, and they have found that a person tends to hang on to the most emotional part of a memory. For example, if someone is shown a scene with an emotional object, such as a wrecked car, in the foreground, they're more likely to remember the emotional object than, say, the palm trees in the background — particularly if they're tested after a night of sleep. They have also measured brain activity during sleep and found that regions of the brain involved with emotion and memory consolidation are active.

"In our fast-paced society, one of the first things to go is our sleep," Payne says. "I think that's based on a profound misunderstanding that the sleeping brain isn't doing anything." The brain is busy. It's not just consolidating memories, it's organizing them and picking out the most salient information. She thinks this is what makes it possible for people to come up with creative, new ideas.

Payne has taken the research to heart. "I give myself an eight-hour sleep opportunity every night. I never used to do that — until I started seeing my data," she says. People who say they'll sleep when they're dead are sacrificing their ability to have good thoughts now, she says. "We can get away with less sleep, but it has a profound effect on our cognitive abilities."

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Journal Reference:

1. Elizabeth A. Kensinger and Jessica D. Payne. Sleep’s Role in the Consolidation of Emotional Episodic Memories. Current Directions in Psychological Science,

Depression appears to be associated with a molecular-level disturbance in the body's 24-hour clock, new research suggests.

Scientists examined genes that regulate circadian rhythm in people with and without a history of depression. As a group, those with a history of depression had a higher level of activity of the so-called Clock gene, which has a role in regulating circadian rhythm, than did people with no mood disorders.

Higher expression levels of this gene suggest something is amiss in the body's 24-hour biological and behavioral cycle, which could affect sleep patterns and other physiological functions governed by circadian rhythm. Sleep disturbance is a common symptom of depression.

But the researchers noted that the association between the gene activity and depression is just that — a link, with no demonstrated causal effect in either direction. At this point in what is known about the relationship, this genetic profile could lead to depression or depression could alter this particular gene function, or some other biological or environmental influences could combine to disrupt the circadian clock.

Though this study offers just a snapshot in time of circadian activity in people with and without depression, the finding could have important clinical implications if it is supported by additional research. People with depression who share this genetic profile might benefit most from sleep-related treatments, such as light therapy or a class of antidepressants that act on melatonin, a hormone that regulates sleep.

"We know that there are a lot of insomnia symptoms in depression, especially early morning awakening," said Jean-Philippe Gouin, a graduate student in psychology at Ohio State University and lead author of the study. "We can't say with this study that there is a direct relationship between this altered gene function and behavior, but the research suggests that over-expression of circadian genes might serve as a biomarker of vulnerability to depression."

The research is published in a recent issue of the Journal of Affective Disorders.

Gouin is currently serving a predoctoral clinical psychology internship at Rush University Medical Center. As a graduate student at Ohio State, he has worked for years on studies led by the Institute for Behavioral Medicine Research that examine the health effects of chronic stress in people who take care of loved ones with dementia. Some of the people who participated in this study were from that population.

"There was some evidence that chronic stress led to changes in circadian gene expression in animals," Gouin said. "We wanted to see if that would be the case in humans, and one of the models of chronic stress in humans is dementia caregiving stress. We found that caregiving was not related to circadian genes, but instead it was really the history of depression that distinguishes between regulation of these genes."

The researchers collected blood samples from, and conducted interviews with, 60 people: 25 who were providing at least five hours of care per week for a family member with dementia and 35 non-caregiving controls with similar demographic characteristics. Thirty participants had a lifetime history of depression, while the other 30 had never been clinically depressed.

All blood samples were drawn between 9 a.m. and 11 a.m. to control for variations in circadian clock gene activity that occur throughout the day.

The researchers analyzed the blood to determine the messenger RNA levels for four circadian genes, including Clock. Messenger RNA (mRNA) contains the set of instructions for building proteins, so its level in genes dictates how much protein each gene is making.

As a group, the participants with a history of depression had a significantly higher level of Clock mRNA expression than did participants who had never been depressed. The researchers didn't find statistically significant results for the other three genes.

The association between depression and elevated Clock mRNA levels held up even when figures were adjusted for differences in age, sex, body mass index, alcohol and tobacco use, exercise, other medical conditions and caregiving status, Gouin noted.

He said that to further define the relationship between this genetic profile and depression, researchers ideally would monitor research participants over time to measure the changes in mRNA expression in circadian genes through a 24-hour cycle.

"If we look at people who have depression, they can have very different groups of symptoms. So if some of them have a biological profile that shows circadian dysfunction, there is a chance that a circadian type of treatment might be more helpful for them than for others," Gouin said.

He conducted the study with co-authors James Connors, Janice Kiecolt-Glaser, Ronald Glaser, William Malarkey, Cathie Atkinson and Ning Quan of Ohio State's Institute for Behavioral Medicine Research, and David Beversdorf of the University of Missouri.

The research was funded by the National Institutes of Health, a General Clinical Research Center grant, a Comprehensive Cancer Center grant and a Fonds de la Recherche en Santé du Québec Doctoral Training Award.

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Journal Reference:

1. Jean-Philippe Gouin, James Connors, Janice K. Kiecolt-Glaser, Ronald Glaser, William B. Malarkey, Cathie Atkinson, David Beversdorf, Ning Quan. Altered expression of circadian rhythm genes among individuals with a history of depression. Journal of Affective Disorders, 2010; 126 (1-2): 161 DOI: 10.1016/j.jad.2010.04.002