I haven't posted in over a week because I was at the annual Sleep meeting in Minneapolis. At the meeting, there were some discussion about sleep, memory, and cognitive performance. So I thought I would post about a recent study done in the Journal of Sleep Research.
In this study, researchers assigned a gambling game to college students. Some of the students learned how to play the game in the morning, and others learned how to play it in the evening. The students then played the game 12 hours later. There was a trick to beating the game, but the students were not allowed to figure that out until they played the game. The results showed that in those that learned about the game in the evening, slept on it, and then played in the AM, 80% of them figured out the trick to the game. In those that learned about the game in the AM and played in the evening, without sleeping on it, only 40% figured out the trick to the game.
The researchers concluded that sleeping on it improved the students' performance. Perhaps it's because during sleep, the brain is able to organize the day's memories, which could have a positive effect on functioning the next day. Research has already shown that memory and performance can be negatively affected by sleep deprivation. This study further enhances are understanding of how sleep can affect the way our minds work. Therefore, when you have an important decision to make or problem to solve, consider sleeping on it first.
Friday, June 17, 2011
Thursday, June 9, 2011
Circadian Rhythm, Gender, and Insomnia
There was a study done last month published in the Proceedings of the National Academy of Sciences about the differences in circadian rhythm between men and women. Our circadian rhythm is the 24 hour cycle that controls many of our bodily functions, including when we sleep.
For this study, the researchers observed the natural circadian cycles of men and women in a controlled sleep lab over 2 to 6 weeks. The results showed individuals circadian rhythms ranged from about 23.5 to 24.5 hours, and was unaffected by age. The circadian clock of women averaged about 6 minutes less than the men, and the women were 2.5 times more likely than the men to have cycles shorter than 24 hours.
The researchers do not know why women's circadian rhythm would be shorter than men's, but it could be related to female estrogen levels.
A circadian rhythm that is short could explain in part why some women may have difficulty maintaining sleep and early morning awakening. It also could mean that women might get sleepy earlier than men. Unfortunately, there isn't anything that can be done to change the length of your circadian rhythm. Practicing good sleep hygiene and listening to your body will help you sleep better.
For this study, the researchers observed the natural circadian cycles of men and women in a controlled sleep lab over 2 to 6 weeks. The results showed individuals circadian rhythms ranged from about 23.5 to 24.5 hours, and was unaffected by age. The circadian clock of women averaged about 6 minutes less than the men, and the women were 2.5 times more likely than the men to have cycles shorter than 24 hours.
The researchers do not know why women's circadian rhythm would be shorter than men's, but it could be related to female estrogen levels.
A circadian rhythm that is short could explain in part why some women may have difficulty maintaining sleep and early morning awakening. It also could mean that women might get sleepy earlier than men. Unfortunately, there isn't anything that can be done to change the length of your circadian rhythm. Practicing good sleep hygiene and listening to your body will help you sleep better.
Monday, June 6, 2011
Obstructive Sleep Apnea and Cancer
At the American Thoracic Society 2011 meeting in Denver, researchers presented interesting results about cancer in mice with experimentally induced obstructive sleep apnea (OSA).
In OSA, patients can have repetitive, brief episodes of low oxygen levels called hypoxia. Persistent, prolonged hypoxemia, as opposed to the repetitve type seen in OSA, has been shown to promote growth of cancer cells. But no study had demonstrated that the intermittent hypoxia in OSA could do this.
Researchers injected melanoma cells in mice. They exposed one half to normal oxygen levels for six hours, and the other half to 20 seconds of hypoxia, 60 times per hour for six hours to mimick what might occur in OSA. The results showed that the melanoma cells proliferated faster in those mice with hypoxia when compared to the mice that were exposed to normal oxygen levels.
This study involves two extremes - normal vs very abnormal, since experiencing 60 episodes of hypoxia per hour for 6 hours would be very severe OSA. We do not know if more mild amounts of hypoxia will also promote tumor growth - more studies will be needed to sort that out.
In OSA, patients can have repetitive, brief episodes of low oxygen levels called hypoxia. Persistent, prolonged hypoxemia, as opposed to the repetitve type seen in OSA, has been shown to promote growth of cancer cells. But no study had demonstrated that the intermittent hypoxia in OSA could do this.
Researchers injected melanoma cells in mice. They exposed one half to normal oxygen levels for six hours, and the other half to 20 seconds of hypoxia, 60 times per hour for six hours to mimick what might occur in OSA. The results showed that the melanoma cells proliferated faster in those mice with hypoxia when compared to the mice that were exposed to normal oxygen levels.
This study involves two extremes - normal vs very abnormal, since experiencing 60 episodes of hypoxia per hour for 6 hours would be very severe OSA. We do not know if more mild amounts of hypoxia will also promote tumor growth - more studies will be needed to sort that out.
Saturday, June 4, 2011
Obstructive Sleep Apnea and Erectile Dysfunction
At the American Urological Association's annual meeting in Washington, DC this year, a study was done of 870 men with an average age of 47.3 years. Health screening revealed 63% of men had obstructive sleep apnea (OSA). I do not have more details about how the men knew they had OSA - 63% seems high.
After adjusting for their age and other health conditions (like diabetes, obesity, and smoking status), researchers found that those men with erectile dysfunction (ED) were more than twice as likely to have OSA than those without ED. The more severe the ED, the greater the likelihood of having OSA.
I use this fact in discussing OSA in my younger male patients, as any mention of ED can get them interested in diagnosis and treatment of OSA. The study does not state that OSA causes ED or is just associated with it. We also do not know if treatment will reverse ED.
Some of my female patients with untreated OSA complain about a diminished sexual libido. There could be a common, underlying mechanism in how untreated OSA impacts sexual functioning in both men and women.
Bottom line is that in men with ED, urologists and primary care physicians should consider untreated OSA as a possible contributor.
After adjusting for their age and other health conditions (like diabetes, obesity, and smoking status), researchers found that those men with erectile dysfunction (ED) were more than twice as likely to have OSA than those without ED. The more severe the ED, the greater the likelihood of having OSA.
I use this fact in discussing OSA in my younger male patients, as any mention of ED can get them interested in diagnosis and treatment of OSA. The study does not state that OSA causes ED or is just associated with it. We also do not know if treatment will reverse ED.
Some of my female patients with untreated OSA complain about a diminished sexual libido. There could be a common, underlying mechanism in how untreated OSA impacts sexual functioning in both men and women.
Bottom line is that in men with ED, urologists and primary care physicians should consider untreated OSA as a possible contributor.
Wednesday, June 1, 2011
Researchers at the University of Louisville have found that a urine test can tell if children who snore have obstructive sleep apnea (OSA) or not. Apparently, there are different concentrations of stress-related proteins the urine of snoring children with OSA, than in snoring children without OSA. The researchers believe that the test is so simple, it could be performed in the home, like a home pregnancy test. It also might eliminate the need for a costly overnight sleep study to determine if children who snore also have OSA.
This study was published in the December 2009 edition of the American Journal of Respiratory and Critical Care Medicine, but I just saw a blurb about it from the University a few months ago. I thought that perhaps more information had come out about this, but a google search only showed the original findings from 2009. I guess we'll have to wait until more studies have been completed.
This study was published in the December 2009 edition of the American Journal of Respiratory and Critical Care Medicine, but I just saw a blurb about it from the University a few months ago. I thought that perhaps more information had come out about this, but a google search only showed the original findings from 2009. I guess we'll have to wait until more studies have been completed.
Monday, May 30, 2011
Cleft Palate and Obstructive Sleep Apnea
Reuters has a summary about the risk of obstructive sleep apnea (OSA) and cleft palate in children. Two otolaryngologists from Children's Hospital of Pittsburgh, Drs. Todd D. Otteson and Jacob G. Robison studied the issue.
The physicians note that OSA is more common in children with cleft palate, whether or not they have a cleft lip, because of the anatomic differences caused by the birth defect and cleft palate surgery, which can reduce airway size. Symptoms of OSA seem to occur most commonly after cleft palate surgical repair, especially the pharyngeal flap procedure for velopharyngeal insufficiency (which can cause speech and swallowing difficulties).
The physicians suggest that surgeons who treat patients with cleft palate will have to weigh the risk of OSA and the need to improve the patient's speech surgically. They also recommends screening for signs and symptoms of OSA and to consider a sleep study if indicated.
The physicians note that OSA is more common in children with cleft palate, whether or not they have a cleft lip, because of the anatomic differences caused by the birth defect and cleft palate surgery, which can reduce airway size. Symptoms of OSA seem to occur most commonly after cleft palate surgical repair, especially the pharyngeal flap procedure for velopharyngeal insufficiency (which can cause speech and swallowing difficulties).
The physicians suggest that surgeons who treat patients with cleft palate will have to weigh the risk of OSA and the need to improve the patient's speech surgically. They also recommends screening for signs and symptoms of OSA and to consider a sleep study if indicated.
Friday, May 27, 2011
Sleep-Wake Behavior and Chronic Fatigue Syndrome
In the journal Sleep, K Rahman et al published a study that assessed the relationship of sleep-wake behavior and chronic fatigue syndrome (CFS). Patients with CFS usually report unrefreshing and restless sleep. To date, scientists have not been able to figure out what makes CFS patients experience the subjective sleep disturbances. In addition, sleep studies have not confirmed objective sleep disturbances in patients with CFS, meaning that there is no evidence that CFS results from a sleep disorder. Researchers do feel that changes in sleep patterns and activity levels can maintain the symptoms of CFS.
This study attempted to determine if circadian rhythm disturbances could be responsible for the fatigue and unrefreshing sleep reported in CFS patients. The results, though, showed no differences in recordings of sleep pattern, sleep duration, daytime activity, or cortisol secretion (a marker of circadian rhythm) between CFS patients and control subjects. The authors concluded that a disruption in circadian rhythm is not associated with CFS.
Interestingly, despite no differences in objective sleep measures, all of the CFS patients in this study reported poor sleep quality. One finding that was different between CFS patients and the control subjects was a loss of vagal modulation of heart rate in CFS patients, which indicates a state of increased sympathetic arousal. Think of vagal modulation (or parasympathetic system) as the brakes of a car and the sympathetic system as the accelerator - thus, in CFS patients, the brakes do not work and the accelerator is going unchecked. There are studies that suggest that normal vagal modulation is needed to make sleep restorative. Therefore, the decrease in vagal modulation could be a biological explanation for the poor sleep quality reported by CFS patients.
It would be interesting to see if medications that increase vagal tone have been reported to make sleep more refreshing. If anyone knows of such reports, put it in a comment here.
This study attempted to determine if circadian rhythm disturbances could be responsible for the fatigue and unrefreshing sleep reported in CFS patients. The results, though, showed no differences in recordings of sleep pattern, sleep duration, daytime activity, or cortisol secretion (a marker of circadian rhythm) between CFS patients and control subjects. The authors concluded that a disruption in circadian rhythm is not associated with CFS.
Interestingly, despite no differences in objective sleep measures, all of the CFS patients in this study reported poor sleep quality. One finding that was different between CFS patients and the control subjects was a loss of vagal modulation of heart rate in CFS patients, which indicates a state of increased sympathetic arousal. Think of vagal modulation (or parasympathetic system) as the brakes of a car and the sympathetic system as the accelerator - thus, in CFS patients, the brakes do not work and the accelerator is going unchecked. There are studies that suggest that normal vagal modulation is needed to make sleep restorative. Therefore, the decrease in vagal modulation could be a biological explanation for the poor sleep quality reported by CFS patients.
It would be interesting to see if medications that increase vagal tone have been reported to make sleep more refreshing. If anyone knows of such reports, put it in a comment here.
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