Wednesday, December 30, 2015

Sleep deprivation and insulin

More research continues to be done on the effects of sleep deprivation on our metabolism. This article summarizes a small study looking at how acute sleep loss impacts insulin sensitivity. Researchers studied healthy, young adults without diabetes. They reduced their sleep time from 9 to 5 hours for five nights in a row - supposedly to simulate how little some may sleep during a workweek. After the 5 short nights, they let the participants sleep 9 hours a night for five more nights. The results showed that the subjects sensitivity to insulin decreased during the 5-hour sleep nights. This means that their bodies had to produce more insulin to keep their blood sugar under control. They didn't develop diabetes, but reduced insulin sensitivity is a precursor to diabetes. The next step will be to assess how less sleep affects older adults and adults with pre-diabetes / diabetes.

Wednesday, November 25, 2015

Sleep apnea and Meniere's Disease

Meniere's Disease involves the ear, and produces symptoms of hearing loss, tinnitus (ringing in the ears), and vertigo (a form of dizziness). Nausea and vomiting often accompany the vertigo. Meniere's Disease is usually treated with medications, but that does not always help. Some research has pointed to an association of poor sleep quality and Meniere's Disease. Obstructive sleep apnea (OSA) can result in poor sleep quality and could worsen Menierie's.

This small study looked at the effect of 6 months of CPAP therapy on Meniere's Disease. All 20 patients had failed medication management of Meniere's Disease. All had OSA diagnosed with a sleep study, and all used CPAP therapy only. They did not restart their Meniere's medications during this study. Results showed that CPAP therapy by itself reduced the impact of the vertigo and the low-frequency hearing loss associated with Meniere's disease.

The reason that treating OSA may help Meniere's is unknown. The study authors speculate that elimination of low oxygen levels when asleep may be the factor that improves the Meniere's. I also wonder if elimination of the snoring helps.

Wednesday, November 18, 2015

Pets and sleep

Lots of people sleep with their pets in their bed. This is fine unless it disrupts your sleep. This article discusses research at the Mayo Clinic showing that 18% of pet owners feel their pets disturb their sleep. The article goes on to discuss how you can get your pet out of your bed if it is bothering your sleep.










Wednesday, November 11, 2015

Control of dream sleep

The neurobiology of sleep is complicated - so many pathways in our brains seem to affect sleep and the different sleep stages. For example, the pons, a part of the brainstem, is thought to be the major part of the brain generating dream sleep. This article and abstract summarize elegant research demonstrating that a group of neurons in the medulla, which is below the pons, can generate signals that start dream sleep. The researchers postulate that these medullary neurons project up into the pons. This finding is interesting in that the medulla is responsbile for unconscious processes that regulate heart rate, blood pressure, and breathing, as well as other autonomic features. These research results may bolster the argument that dreams are not from the conscious brain, but more of an automatic process like breathing or heart rate. Unfortunately, these findings don't help us understand the function of dreaming any better than our current understanding.

Wednesday, November 4, 2015

Restless legs syndrome and cardiovascular disease and kidney disease

Restless legs syndrome (RLS) is a chronic neurological condition that causes discomfort in the legs in the evening before sleep. Studies have linked RLS with certain cardiovascular diseases such as high blood pressure. This article is about a study that examined RLS in veterans. Specifically, the researchers studied the relationship between RLS and stroke, heart disease, kidney disease, and mortality rate. The researchers compared about 3700 veterans with and without RLS. Results showed higher amounts of stroke, coronary heart disease, chronic kidney disease, and mortality in those that had RLS compared to those that did not.

The results are not surprising. And as the article points out, the findings don't show that RLS causes strokes, heart disease, or kidney disease. One issue is whether the RLS in these veterans was primary, or secondary to another disorder, such as obstructive sleep apnea (OSA). OSA can significantly worsen RLS, meaning that it may be the OSA that is increasing the incidence of cardiovascular or kidney disease - not necessarily the RLS. Also, RLS is known to be common in patients with chronic kidney disease, especially those on dialysis. More studies are needed to tease out the relationship between RLS and these other disorders.

Wednesday, October 28, 2015

Sleep patterns of traditional societies

Here is an interesting article about a research study that received lots of media attention. The researchers studied the sleeping patterns of three traditional societies in Africa and South America - apparently their lifestyles resemble ancient hunter-gatherers. Results showed that the three groups slept 6 hours and 25 minutes per night on average. The sleep duration was similar between the three groups. Despite getting only 6'25" of sleep per night, the participants did not complain of feeling sleepy in the daytime and very rarely took naps.

A surprising result was that natural light did not affect the timing of sleep, as all three groups fell asleep on average 3.3 hours after sunset - which is the time when the temperature was falling. Even more interesting was that all of the group members woke up when the temperature was at its lowest.

Of note, insomnia was extremely rare - two of the groups did not even have a word for it!

Wednesday, October 14, 2015

Sleep and heart disease

Certain sleep disorders such as obstructive sleep apnea have been linked with cardiovascular disease. This article reviews research about sleep duration and quality and coronary artery disease. I only have access to the article and the abstract. Researchers asked subjects to rate their sleep quality and the amount of sleep they get. The results showed that those who slept 5 or less hours, or 9 or more hours, had increased rates of coronary artery calcification and stiffness - both of which are early signs of coronary artery disease.

As far as I can tell, sleep quality and duration were assessed via questionnaire. There was no sleep study or other objective sleep duration measurement such as actigraphy. So it could be that some of the subjects had poor sleep quality from un-diagnosed obstructive sleep apnea, and that could account for some of the increased rates in coronary artery disease.

Wednesday, September 30, 2015

CPAP use, obstructive sleep apnea, and cardiac function

Studies have shown that obstructive sleep apnea (OSA) can negatively impact cardiac function, especially if the OSA is severe. And studies have shown that treating severe OSA with CPAP can improve cardiac function. However, studies have not shown clearly that treating milder cases of OSA provides significant cardiac benefit.

This study looked at patients with mild-to-moderate OSA with mild cardiac dysfunction. Patients were minimally symptomatic with regards to OSA as well. Patients were either given CPAP for 6 months or given no CPAP. Compliance with CPAP was determined based on the CPAP download. The results did not show any convincing change in cardiac function or structure after 6 months of CPAP usage. There was no dose response effect with CPAP usage either, meaning that there still was no change in cardiac function in those that used CPAP the longest per night.

The researchers concluded that CPAP use in patients with mild OSA and mild cardiac dysfunction may not be as helpful as traditional cardiac dysfunction treatments like blood pressure medications.

Wednesday, September 23, 2015

Obstructive sleep apnea may disrupt the blood brain barrier

The blood brain barrier is like a wall that has holes in it. It allows good substances to cross from the blood vessels into the brain. At the same time, it keeps out harmful substances like bacteria and some toxins. According to this article, researchers think that some illnesses may result from the breakdown of the blood brain barrier.

The article discusses a research study showing that untreated obstructive sleep apnea (OSA) can breakdown the blood brain barrier. The researchers think that the low oxygen levels associated with OSA are responsible for the breakdown. But the breakdown may be what causes some of the symptoms of OSA, such as memory or mood problems. The researchers also think that repairing the blood brain barrier may improve these symptoms in patients with OSA. I also wonder if treating the OSA repairs the blood brain barrier - more studies will be needed to figure that out.

Wednesday, September 9, 2015

Magnetic stimulation may improve nighttime bedwetting

Nighttime bedwetting, also called nocturnal enuresis, can cause family problems and embarrassment to the person suffering with it. Obviously all of us start out life as a bedwetter, but most develop nighttime control at around 5 or 6 years of age. The causes of enuresis are variable, with some cases being the result of obstructive sleep apnea (OSA). Treating the OSA improves the nocturnal enuresis.

This study evaluated the effect of magnetic stimulation on nocturnal enuresis. Researchers put the magnet over the subjects lower back, just above the tailbone. The magnet was turned off and on rapidly 5 times per week. The results showed significant reduction in nocturnal enuresis frequency. Sham magnetic stimulation also showed a reduction in nocturnal enuresis frequency that was almost as large as the real magnetic stimulation. However, the frequency of enuresis returned to baseline after the sham magnetic therapy was stopped. In the real magnetic stimulation group the effect persisted a month after therapy was stopped.

Wednesday, August 26, 2015

Sleep-related breathing disorders, functional disorders, and anxiety disorders

Here is a fascinating article (at least to me) about a possible link between sleep-related breathing disorders like obstructive sleep apnea and other disorders. The other disorders are classified as "functional", meaning no etiology is agreed upon, such as fibromyalgia, chronic fatigue syndrome, and migraines. The other disorders include anxiety disorders like panic attacks and post-traumatic stress disorder (PTSD).

The researcher that is discussed in article is Dr. Gold at Stony Brook University and has published research studies on this topic. His theories about how mild OSA disorders can worsen functional and anxiety disorders is not without controversy. However, if further research confirms his theories, treatment for OSA may also help these difficult-to-treat disorders.

Wednesday, August 19, 2015

Sleep and memory

Research has shown that sleep is connected to memory. This article discusses research about that topic. I don't have access to the original research study, only the summary article provided in the link. The study setup had participants learn made-up words prior to a night of sleep or the same amount of time awake. The participants were then asked to recall the words after a period of sleep or wakefulness.

The results showed that when compared to wakefulness, sleep helped the participants recall forgotten words. One of the researchers concluded that "sleep almost doubles our chances of remembering previously unrecalled material. The post-sleep boost in memory accessibility may indicate that some memories are sharpened overnight. This supports the notion that, while asleep, we actively rehearse information flagged as important."

Wednesday, August 5, 2015

Sleep and long distance running

This article isn't just about sleep. It's about a runner who does ultra-marathons - typically 50k or 100k races. This runner broke the unofficial record for completing the Appalachian Trail. He finished the 2189 mile journey in only 46 days - this comes out to be 47.5 miles per day! I've ran a marathon and have done many 3-5 night backpacking trips in the Smoky Mountains, but I can't imagine walking or running 47.5 miles per day. What an amazing feat.

The reason I am blogging about this, though, is because the article mentions how the runner only got 4-5 hours of sleep per night. On the last few days, he only got 1-2 hours per night! So this elite athlete could continue to function at his high level even with very little sleep. This fact is interesting because some studies show that athletes perform better when they get plenty of rest. The article doesn't say how much sleep the runner typically gets when not racing. It may be that he only sleeps 5-6 hours on a regular night - so 4-5 hours of sleep would not be that much deprivation.

Wednesday, July 29, 2015

Sleeping with your phone

This article discusses survey data about cell phone use. The results showed that 71% of those surveyed sleep with their cell phone near them. Most have it on their nightstand, but some have it on the bed or even in their hand. The article reports that only 24% of those surveyed keep their phone in a separate room, which is consistent with good sleep hygiene.

I don't agree that keeping your cell phone out of your bedroom is good sleep hygiene. I keep mine next to my nightstand every night. For me, my phone serves as my pager for when I am on call but also as my alarm. The problem with having a cell phone in your bedroom occurs when you use the phone to help you fall asleep, rather than learning to fall asleep on your own. Or if you get texts, email alerts, or calls all night from friends and family - this will disturb your sleep. But just having the phone next to you is not necessarily a problem.

Wednesday, July 22, 2015

Jaw surgery for obstructive sleep apnea

For most people with obstructive sleep apnea (OSA) that is at least moderate severity, CPAP is the most effective treatment option. However, for the right patient, jaw surgery can be very effective as well. The type of jaw surgery that is done is where the oral surgeon breaks the lower (and usually the upper) jaw to reposition it away from the face. This opens up the breathing tube, resulting in less obstruction. There is data showing short term effectiveness of this procedure, but little long term efficacy data. This study does just that.

The study participants were adults who had moderate or severe OSA. Sleep studies were done pre- and post-op jaw surgery, as well as at least 2 years after the surgery. Results showed that the average OSA severity reduced by almost 77% over the long term. And 47% of patients did not meet criteria for OSA post-op. Finally, 83% of patients had mild OSA but no excess sleepiness post-op. Blood pressure was decreased and quality of life increased after the jaw surgery. These improvements in OSA severity and blood pressure occurred despite an increase in weight during the followup period.

Wednesday, July 15, 2015

Napping, impulsivity, and frustration tolerance

Sleep loss can increase the chances of acting impulsively as well as the ability to handle frustration. And for some people, extra sleep can improve frustration tolerance and decrease impulsive behavior. This article is about research on how planned napping may help. I don't have access to the full article, so I can only discuss what's in this article.

The researchers studied 40 adults, ages 18-50 years old. They had the participants keep a regular sleep schedule for three nights and then they completed a series of computer tasks and answered questions. The participants were then randomized to either have a 60 minute nap or watch a nature video before doing the tasks and answering questions again. The results showed that the participants who napped were less impulsive and had better frustration tolerance.

The article attempts to link the study results to workplace productivity but I don't think the study was designed to evaluate that specifically. However, I could see how better-rested employees may perform better. But that productivity advantage may be offset by an hour nap at work!

Monday, July 6, 2015

Sleep as a vital sign

When I was in medical school, the four vital signs were blood pressure, pulse, breathing rate, and temperature. Over the years, pain level has been added to the list of vital signs by some medical practices and hospitals. Here is an interesting article advocating for assessment of sleep during routine medical visits, much like the way vital signs are automatically assessed with each patient encounter.

The authors note how sleep disorders are under-diagnosed, and how sleep disorders can affect so many other areas of a person's health. Also, many non-sleep disorders affect how a patient sleeps. At the end of the article, the authors pose a question as to how to assess a patient's sleep during a routine visit. Unfortunately, there is no rapid objective measure of sleep quality that can be used during a routine visit, like how we measure blood pressure. So an assessment of sleep is subjective, like the assessment of pain. Many non-sleep physicians already ask questions such as "How are you sleeping?". Perhaps having a patient rate their sleep quality on a scale of 1 to 10, similar to how some clinicians assess pain levels? That would be an interesting research project to do.

Wednesday, June 17, 2015

Insomnia and empathy

Insomnia can significantly affect your daytime functioning - most with chronic insomnia report daytime tiredness, concentration problems, and irritability. Here is an article about research presented at the annual Sleep meeting in Seattle. Researchers studied how insomnia levels affect healthcare workers ability to feel empathy for their patients. Workers with a sufficiently high insomnia scored demonstrated less empathy than those with lower insomnia scores. The article doesn't specify whether the healthcare workers had temporary insomnia, long term insomnia, or just sleep deprivation from rotating work and call schedules.

Wednesday, June 10, 2015

Micro-CPAP

I've been asked by multiple patients in the past few weeks about this tiny CPAP, the Airing. I don't know anything about it other than what is in this article. It looks interesting, but I have many questions about it. If it gets FDA approval, we will learn much more.

Wednesday, June 3, 2015

Natural history of excessive daytime sleepiness

This article examines the natural history of excessive daytime sleepiness (EDS). In the article, the authors explain that EDS affects about 30% of the general public. They also explain that EDS is associated with certain psychiatric, metabolic, and sleep disorders. I would add that EDS is also a result of insufficient amount of sleep and sedating medications.

In this study, participants had a comprehensive sleep history and physical exam along with an in-lab overnight sleep study at baseline. No daytime sleepiness study, called the Multiple Sleep Latency Test (MSLT), was performed - sleepiness was only determined subjectively. Sleep apnea was defined at a cutoff that is standard for moderate severity - it's not explained why they did not include those with mild sleep apnea, who could be just as sleepy as more severe levels. Finally, follow up was only through telephone interview - no repeat sleep study or physical examination was done. The follow up was 7.5 years after the baseline evaluation, on average. Therefore, there are some important limitations to this study.

Incident EDS was defined as those who had no EDS at baseline but did have it at follow up. Remitted EDS meant those that had EDS at baseline, but not at follow up. And persistent EDS meant those that had EDS at both baseline and follow up. Results showed that incident EDS was 8.2%, and was more commonly associated with male gender, non-Caucasian race, and younger and older age. Depression, sleep apnea, obesity, and diabetes were also associated with incident EDS. Sleep duration less than 5 hours or more than 8 hours was associated with incident EDS. However, insomnia was not associated with incident EDS. Snoring was related to incident EDS, especially in those with sleep apnea.

The persistent EDS rate was 38%, whereas 62% had remitted EDS. Persistent EDS was associated strongest with anemia and insomnia. Individuals with incident or persistent EDS gained significantly more weight when compared to those without EDS. Also, individuals with remitted EDS gained significantly less weight compared to those without EDS.

The authors concluded that obesity, depression, and sleep disorders should be a public health priority to improve EDS.

Wednesday, May 27, 2015

CPAP therapy and cognitive performance in elderly patients with severe obstructive sleep apnea

Obstructive sleep apnea (OSA) is more common with age, regardless of weight. OSA in elderly patients can contribute to daytime sleepiness and impair cognitive performance. OSA has even been associated with development of early dementia, called mild cognitive impairment. There is not a lot of data showing the effects of CPAP use on cognitive functioning in elderly patients. But that is just what this study sought to do.

The study population was a subset of a larger study, and participants were at least 65 years old. Participants received extensive neuropsychological testing at the start and end of the study period (6-10 years between the two time points). Participants had a sleep study at the beginning of the study and only those with severe OSA were included. The researchers then divided the participants into those that used CPAP therapy and those that did not. This was a smaller study, with only 126 subjects included, 33 of which used CPAP. Also, note that CPAP use was determined by the patient's self-report. In other words, CPAP use was not determined objectively by checking what the CPAP machine had recorded. So it's possible that CPAP use may have been over-estimated. The researchers also did not separate out CPAP use into the number of hours per night - participants either did or did not report CPAP use. Interestingly, all of the CPAP users reported using CPAP for the minimal 4 hours per night. Finally, participants who used CPAP tended to have more severe OSA, were more overweight, and had more daytime sleepiness. There was no difference in age, gender, or level of education in those that used CPAP versus those that did not.

The results showed that subjects with OSA had a more severe deterioration of cognitive function and memory over time. Also, CPAP therapy helped preserve some cognitive functions like memory, attention, and decision making ability. The authors concluded that long term CPAP use is associated with a protective effect on cognitive performance in elderly patients with severe OSA. They suggest that physicians who treat elderly patients consider screening for and treating OSA to help maintain cognitive performance.

Wednesday, May 20, 2015

CPAP and blood sugar levels in Prediabetes

Prediabetes is a condition in which blood sugar levels are elevated above normal, but not high enough to meet criteria for diabetes. Here is a study that measured blood sugar levels (and other parameters) during two weeks of CPAP use versus an oral placebo in patients diagnosed with obstructive sleep apnea. I only have access to the abstract and an article about the study. In this study, researchers ensured that those randomized to CPAP used it for 8 hours a night for two weeks straight. The results showed that the CPAP users had lower blood sugar levels as the main outcome. A secondary outcome measure showed lower blood pressure levels in the CPAP users when compared to the controls.

Wednesday, May 13, 2015

Bedtime routines and children's sleep

In my practice, I recommend that all parents follow a regular bedtime routine with their younger children. Research has shown that a consistent bedtime routine is linked to better sleep in kids. However, there are no studies that have looked at whether a bedtime routine works better if done every night or just once a week. This study did just that. It involved a questionnaire of over 10,000 moms who had children up to 5 years old. Results showed that less than half of all families had a consistent bedtime routine every night. In those families with a consistent bedtime routine, the children had earlier bedtimes, shorter time to fall asleep, fewer number and duration of awakenings, and more total sleep per 24 hours. Also, there was a linear relationship between number of nights per week of bedtime routine and sleep outcomes - meaning that the more times per week there was a bedtime routine, the better the sleep outcomes. Perceived sleep problems also went up as the number of bedtime routine nights per week went down. Finally, there was a relationship between daytime behaviors (including hyperactivity, attention deficit, and difficult behaviors) and consistent bedtime routine. Again, the relationship was such that a more frequent bedtime routine meant less problematic daytime behaviors.

The authors conclude that pediatricians could easily recommend a consistent bedtime routine to all of their patients. Pediatricians could explain that a bedtime routine is a set of the same activities done in the same order on a nightly basis prior to turning the lights out. For example, brushing teeth, putting on pajamas, and then reading a story before turning out the lights.

Wednesday, May 6, 2015

Pictures of infants' sleeping positions in media

Here is an interesting abstract presented at the Pediatric Academic Societies annual meeting in San Diego. I didn't attend this meeting, but saw a write-up about this abstract here. The abstract is about a study designed to evaluate images in popular stock photograph websites and pictures of infants in magazines published for women of childbearing age. The study authors were attempting to determine if the pictures were in compliance with the American Academy of Pediatrics guidelines for safe infant sleep practices - meaning having your infant sleep on its back to prevent Sudden Infant Death Syndrome (SIDS).

The results showed that just over half (50.3%) of the stock photos from websites showed the baby sleeping on its back. And only 15.7% of all infant sleep environments were compliant with American Academy of Pediatrics recommendations - meaning that the infant was not bed-sharing and the crib did not have soft objects like pillows, blankets, or bumper pads. With regard to the magazine pictures, there were 4 out of 12 pictures showing an infant sleeping on its stomach, which may raise the risk of SIDS. And only 7 of 24 magazine pictures properly demonstrated a safe infant sleep environment.

The study authors are concerned that stock photo websites and magazine pictures of infants sleeping in positions and environments not recommended by the American Academy of Pediatrics could confuse some women, causing them to think it's ok to let their infant sleep on its stomach, for example.

Wednesday, April 22, 2015

Obstructive sleep apnea and tooth wear

In my practice, I see lots of patients with excessive tooth wear, or irreversible loss of the tops of the teeth. It gets more common with age. It's not always due to teeth grinding - it can occur from eating certain foods, especially those high in acidity. This study looked at the association between tooth wear and obstructive sleep apnea (OSA). This was a study done in a private dental clinic in Spain, and patients diagnosed with tooth wear each had an overnight home sleep study to assess for OSA. The results showed that the prevalence of OSA was three times higher in patients with tooth wear. And there was a positive correlation between OSA severity and tooth wear, meaning the more severe the OSA, the more severe the tooth wear. The relationship was not diminished after controlling for body mass index, age, and gender.

The study authors speculated that there could be a common mechanism behind the OSA and tooth wear, such as arousal from sleep contributing to tooth clenching or grinding. The study authors also pointed out that the association between OSA and tooth wear could be coincidental, as both conditions become more prevalent with advancing age.

Finally, the study authors recommended that dentists consider referring patients with tooth wear to their primary care provider or sleep doctor for evaluation of possible OSA.

Wednesday, April 15, 2015

Sleep apnea and high blood pressure

Another post about obstructive sleep apnea (OSA) and high blood pressure (HTN). This study is a meta-analysis of observational studies and randomized controlled clinical trials. The study authors studied patients with resistant HTN, meaning blood pressure that was not responding to multiple medications. The study participants also had OSA.

I don't have access to full article, only the link above and the abstract. The results suggest that those patients with the highest blood pressures had the greatest reduction in blood pressure after using CPAP therapy. The study authors concluded that untreated OSA may be why some patients' blood pressure just won't come down with multiple medications.

The results from this study are not new, but do provide more evidence of the importance of screening patients with resistant HTN for underlying OSA. In my community, primary care doctors have been doing this for years already. However, this may not be the case in other medical communities around the country.

Wednesday, April 8, 2015

Blood pressure and sleep apnea

Several research studies have linked high blood pressure (HTN) to obstructive sleep apnea (OSA). The etiology is not clear, however. With OSA, there is sleep disturbance from brief awakenings, thought secondary to adrenaline release that is triggered when breathing resumes. Also, oxygen level reductions, called desaturations, could lead to elevated blood pressures. Respiratory events that are detected during a sleep study have specific scoring criteria - the event has to last at least 10 seconds and result in either a brief arousal from sleep and / or an oxygen desaturation.

This study sought to determine which types of respiratory events were most likely to result in HTN. The researchers followed 2040 participants and used sophisticated statistical models to study the sleep study results and blood pressure measurements. Results showed that those respiratory events with at least a 4% oxygen desaturation were most consistently associated with HTN. Interestingly, the other sleep study measurement that correlated with HTN was periodic limb movements that resulted in brief arousals from sleep.

Wednesday, April 1, 2015

CPAP use after weight-loss surgery

Obstructive sleep apnea (OSA) and obesity are related. Weight loss can improve OSA, sometimes enough to eliminate it altogether. However, if OSA is severe, weight loss alone is often not enough to cure OSA.

Most patients who undergo weight loss surgery have OSA, and most use CPAP prior to weight loss surgery. Unfortunately, most patients discontinue their CPAP use after weight loss surgery. This study assessed long-term CPAP use in 21 patients who had undergone gastric banding. Results showed that body-mass index significantly increased by 6.8 in those patients who did not use their CPAP after weight loss surgery. And BMI dropped by 1.8 in those patients that were adherent to CPAP therapy after weight loss surgery.

Another important point is that OSA persisted in almost all of the patients who underwent the surgery, despite the substantial weight loss (average 121 pounds lost). And, after 7.2 years of follow up, the majority of patients had gained back some weight (22 pounds).

So the data in this study suggest that CPAP adherence for the long term may help with weight loss maintenance. Remember this is a small study though. Other confounding factors could contribute to reasons why some patients chose to keep using CPAP. For instance, some may have continued only because using CPAP made them sleep better or have more energy. And that increased energy could have helped them keep exercising, which may help maintain weight. Or those that kept using CPAP may have adhered better to diet restrictions.

In the end, follow up with the sleep medicine specialist is important after weight loss surgery. In that way, post-operative OSA severity can be assessed after the first year. Then, the patient and sleep medicine physician can discuss the pros and cons of continuing CPAP therapy if necessary.

Wednesday, March 25, 2015

Sleep and learning

Although the exact details are unknown, researchers believe that sleep is helpful in integrating and strengthening new memories. When I was a fellow, it was thought that this occurred mainly in dream (REM) sleep. Here is an article that studied the effect of slow wave sleep (SWS), a deep non-dream state, on memories related to fear. Apparently, studies have shown that memories can be reactivated during SWS by a reminder cue like odors or sounds experienced during SWS.

In this study, researchers used a conditioning procedure in humans to elicit a fear response. Specifically, they repeatedly paired a neutral sound with a mild electrical shock to the wrist of the participants. After enough pairings, the neutral sound would cause a measurable fear response in the participant, even without the electrical shock. In other words, the participant learned that the neutral tone meant the electrical shock was coming. After this conditioned learning, the participants slept for 4 hours because the first 4 hours of sleep are dominated by SWS. The second half of sleep is dominated by REM sleep, and the researchers wanted to isolate the effects of SWS.

One way to eliminate the learned fear response that has become paired with a conditioned stimulus like a neutral tone is to repeatedly expose the subject to the neutral tone but without the electrical shock. Over time, the neutral tone will stop causing the fear response as the subject learns that the electrical shock no longer is associated with the neutral tone. So in the study, the researchers played the neutral tone without the electrical shock during SWS. Results showed that this was able to attenuate the fear response. And this was compared to other subjects that received a different tone than the neutral tone and in those that received no tones at all. Finally, exposure to the tones in SWS did not appear to negatively affect sleep architecture or sleep quality.

So what does all this mean? Well in psychology, when someone has pathological fear or post-traumatic stress disorder, one effective treatment is to repeatedly expose the patient to what they fear, so that their fear response gradually attenuates. It's very challenging therapy for patients, because they have to consciously subject themselves to their fears. But, as this study suggests, maybe patients with pathological fear can be exposed to the feared stimulus during SWS, and not have to experience it consciously in order to reduce the fear response. Here's an analogy...it would be like going from having your appendix taken out while awake to having it taken out under anesthesia.

Wednesday, March 18, 2015

Sleep apnea, motor vehicle accidents, and CPAP therapy

There are recent meta-analyses showing higher risk of motor vehicle accidents (MVA) in those with obstructive sleep apnea (OSA), and a lower risk of MVA with CPAP therapy. However, the conclusions from these studies is somewhat limited due to possibly faulty research designs. In other words, it's still uncertain how much risk OSA imparts and if CPAP really reduces that risk. However, this study, recently in the Sleep Journal, set out to determine just that, using a well designed protocol. It was a retrospective study of almost 1500 drivers in Sweden. The results showed that there was a 2.5 fold increase in risk of MVA in patients with OSA. The risk was highest in older drivers. Also, risk was highest in those with high subjective sleepiness, but the risk did not depend on OSA severity. And the incidence of MVA was reduced by 70% among patients that used their CPAP at least 4 hours per night. Interestingly, risk of MVA was increased by 54% among those that used CPAP less than 4 hours per night.

The authors concluded that because CPAP therapy can improve sleep quality and overnight oxygenation, it could improve alertness and driving performance - leading to less MVA's.

Wednesday, March 11, 2015

Sleep duration and stroke risk

I've blogged here and here about stroke risk and sleep duration. The data suggest a U-shaped curve with regards to stroke risk and amount of sleep. This means that those who are short or long sleepers are at increased risk.

This study also examined stroke risk and sleep duration. The data was from a larger cohort study and included over 16,000 participants. Sleep duration and sleep quality were assessed with a self-reported questionnaire. The researchers divided up the participants into short sleeper (<6 hours per night), average sleeper (6-8 hours per night), or long sleeper (> 8 hours per night). Of note, this is an arbitrary definition, although generally agreed upon in our field.

Results showed a J-shaped curve, meaning that longer sleepers had a 46% higher risk of a stroke after adjusting for the usual cardiovascular risk factors. Of note, this result was only significant for those aged 63 and older. And the association remained even if the participant reported sleeping longer, but had good sleep quality.

Short sleepers had an 18% increased risk of stroke, but this was not statistically significant. Both groups were compared to the stroke risk of average length sleepers.

The authors concluded that long sleep duration may be an early sign of increased stroke risk, particularly among healthy people.

Wednesday, March 4, 2015

Later school start times for teenagers

School start times are a hot issue these days. Particularly, letting teenagers start school later, to match their natural pattern of sleeping in later than younger kids. This report is about a survey done at the University of Michigan where researchers asked parents how they felt about later school start times. Below is a figure from the report that shows some of the results of the survey.


Most of the parents (88%) said their teens currently have a start time before 8:30 a.m. Among these parents, 27% of parents would support a school start of 8:30 a.m. or later only if it did not impact the school budget, and 24% would support a later start time regardless of impact on the school budget. Less than one-half (49%) of the parents do not support a later school start time.

Wednesday, February 25, 2015

Sleep duration in American teens

On the heels of last week's post about new sleep duration recommendations, this post is about an article in the journal Pediatrics about the changes in sleep amounts among teens in the United States from 1991 to 2012. The participants were 270,000 8th, 10th, and 12th graders involved in a larger survey. The researchers asked the participants two questions about sleep duration. One was how often they got less 7 hours or at least 7 hours of sleep. The other question was how often the teen felt they got enough sleep per week.

Epidemiological studies show that almost a third of teens don't get enough sleep. The reasons are not known, but researchers speculate that internet, social media, and increased competitiveness of the college admissions process are contributing. And, in last week's blog, I posted a table that recommends 8-10 hrs per night for 14-17 year olds.

The results of the current study showed that self-reported sleep duration in teens has decreased over the past 20 years. The largest decrease was in 15 year olds. Although the data show that sleep duration declined across all age groups and major socio-demographic subgroups, results showed that female students, racial/ethnic minorities, and students of lower socio-economic status (SES) reported getting at least 7 hours of sleep less often than male subjects, non-Hispanic white subjects, and students of higher SES.

Wednesday, February 18, 2015

New sleep duration recommendations

Here is an article that discusses the National Sleep Foundaion's latest sleep duration recommendations. One thing that caught my attention is that sleep duration for adults is broken up into 3 categories - young adult, adult, and older adult. This makes sense to me from a physiological perspective, as older adults may not need as much sleep as 20 somethings.

Wednesday, February 11, 2015

Nasal surgery and CPAP

Most of my patients with obstructive sleep apnea (OSA) report they are "mouth breathers" at night. Because of that, they often think they should use a CPAP mask that covers their nose AND mouth...the full face mask. Full face masks often leak excessively, especially for side sleepers. I find that most of the time, my patients do well with a mask that just covers their nose or goes right in their nose (nasal pillows). But I have a small segment of patients who really struggle to breathe just through their nose. Almost all of these patients have daytime nasal stuffiness as well. Often, airflow through their nose is not improved with by-mouth medications or nasal sprays. In these cases, patients can opt to use the full face mask, or consider surgical therapy to improve nasal airflow. If the Ear, Nose and Throat (ENT) physician determines there is significant anatomical obstruction, then surgical therapy may improve nasal airflow enough to allow the patient to utilize an over-the-nose mask, instead of the full face mask.

Here is a study supporting my clinical experience. It's a meta-analysis of current literature. After examining past studies, the authors concluded that nasal surgery to relieve obstruction resulted in an average lowering of CPAP pressure by 2.66 cwp. Regardless of nasal surgery type, CPAP pressures were lower on average 1.9 cwp between preoperative and postoperative periods. The greatest difference was in those patients undergoing combined septoplasty with turbinoplasty. Finally, overall CPAP use increased after nasal surgery, possibly due to overall lowered CPAP pressures. The study did not mention changes in mask styles after surgery, such as from full face mask to nasal mask. This change alone, even without reduction in CPAP pressure may improve CPAP adherence.

Wednesday, February 4, 2015

Treating obstructive sleep apnea with medication

Obstructive sleep apnea (OSA) is currently treated with mechanical devices - air pressure from CPAP, jaw movement with oral appliance therapy, or surgical therapy. No medications have been shown to be particularly helpful in treating OSA. This article discusses NIH funding given to a team of researchers at the University of Chicago.

The article describes the research already going on at the University that focuses on a small group of cells in the carotid artery called the carotid bodies. When levels of oxygen in the blood drop, these carotid bodies send signals to the brainstem to increase breathing, with the goal of increasing oxygen levels in the blood. The article describes that in sleep apnea, the carotid bodies may not react appropriately, and thus stop sending signals to the brain. The University of Chicago team has developed a compound that may help the carotid bodies to keep working properly during sleep apnea, and thus aid in their regulation of breathing - at least in rodents.

However, it's not clear what type of sleep apnea the researchers are working on. It sounds like central sleep apnea (CSA), which is a completely different, and less common form of sleep apnea, than OSA. In most cases of OSA, the drive to breathe is intact, but airflow is significantly reduced due to a blockage in the upper airway. In addition, not every patient with OSA has oxygen level reductions, even though airflow through the upper airway is reduced. But if a person with OSA has regular blood oxygen level reductions, perhaps a medication that helps the carotid bodies stimulate breathing may be effective, if that stimulation involves increasing the diameter of the upper airway.

Wednesday, January 28, 2015

Asthma and obstructive sleep apnea

This article is about a study showing an association between asthma and risk of obstructive sleep apnea (OSA). All participants were adults drawn from a random sample of Wisconsin state employees. Initially they were free of OSA based on overnight sleep studies done every 4 years. Results showed that the relative risk of developing OSA was 1.39 times higher in those with asthma. And this was after adjusting for sex, age, baseline and change in body mass index, and other factors. The study authors suggest that physicians who treat asthma should periodically screen those patients for OSA.

Wednesday, January 21, 2015

Sleep and screen time in children

Studies have been demonstrating that some children are getting too little sleep, and that technology is driving some of the sleep deprivation. Studies have also shown that TV in a child's bedroom has been linked to less sleep. And interactive media devices like smart phones and video games may be more disruptive to sleep. This is in contract to TV viewing, which is a passive activity. Also, interactive devices are held very close to the face, meaning that light from the screens on these devices is more likely to interrupt melatonin secretion at night, which may further disrupt sleep. Finally, these interactive devices can disrupt sleep by text messages, which is not a problem with TV viewing.

This study was a cross-sectional survey of about 2000 4th and 7th graders in Massachusettes. They asked children about their TV viewing, small screen use (like cell phone, Ipad, etc), and various sleep parameters. Results showed that 54% of kids slept near a small screen and 75% slept with a TV in the room. Not surprisingly, a higher proportion of seventh graders slept near a small screen than 4th graders.

Children who slept near a small screen reported 21 fewer minutes of sleep per weekday when compared to those who did not sleep near a small screen. This effects was independent of having a TV in the room. Children who slept in a room with a TV reported sleeping 18 fewer minutes during the weekday than those without a TV in their room. This was independent of sleeping near a small screen. The results showed that the association between the screens and sleep duration resulted from a later bedtime. Sleeping near a small screen, but not a TV in the room, was associated with a 1.39 times the prevalence of perceived insufficient sleep or rest, even after adjusting for sleep duration. Not surprisingly, longer time watching TV or playing video games was associated with shorter weekday sleep duration, again accounted for by later bedtimes. And each hour spent watching TV or playing video games was associated with a higher prevalence of perceived insufficient sleep or rest. Interestingly, physical activity reduced the association between video games and perceived insufficient rest or sleep.

The study authors concluded that the small screens affect sleep quality more than TV viewing because of the stimulating content, calls, and audible text messaging while sleeping. They also mentioned that other mechanisms may contribute. For example, consuming caffeinated beverages near bedtime, evening exposure to bright light, and increased cognitive / emotional / physiologic arousal after playing video games, interacting on social media, or watching exciting / frightening TV content.



Wednesday, January 14, 2015

Obstructive sleep apnea in childhood and adolescence

There is limited study data about the natural course of obstructive sleep apnea (OSA) in children. This study looked at OSA incidence and remission from middle childhood (ages 8-11 years) through late adolescence (ages 16-19 years). It also studied if risk factors for OSA that were present in middle childhood remained in adolescence. This was a retrospective study from a larger sleep and health study.

Of note, OSA in children is typically defined as full or partial collapse of the airway at least 1 time an hour. In this study, the authors used a more conservative measure of 5 or more airway collapses per hour. The results showed OSA was present in 4.7% of middle childhood aged kids and in 4.3% of adolescents. And only 8.7% of those with OSA in middle childhood still had OSA in adolescence - meaning almost 91% of cases of OSA resolved between middle childhood and adolescence. And of those whose OSA had remitted by adolescence, only 24% had had tonsillectomy, the treatment of choice for OSA in children. So in 3 out of 4 cases, the OSA went away on it's own, without surgical intervention. Of the children without OSA, only 4% went on to be diagnosed with OSA in adolescence.

Unlike OSA, habitual snoring was much more persistent from middle childhood to adolescence. Half of the snorers in middle childhood were still snoring in adolescence, yet most of them did not go on to develop OSA as adolescents. However, when the study authors lowered the threshold for diagnosing OSA, 32% of middle childhood snorers went on to develop OSA in adolescence.

Risk factors for middle childhood OSA were African American race, preterm status, and neighborhood distress. However, these were not risk factors for OSA in adolescents. Instead, the risk factors were male sex and history of tonsillectomy or adenoidectomy. Finally, adolescents with OSA had a higher body-mass index (marker for obesity) compared to adolescents and middle childhood kids without OSA. The authors speculated that the changing risk factors may reflect the fact that upper airway changes occur from middle childhood to adolescence, especially regression of tonsils. Thus, other factors like male gender and obesity would be more important in adolescents. The authors go on to explain that the risk factor of prior tonsillectomy in adolescents with OSA may be due to other risk factors that reflect a predisposition for upper airway collapse in sleep.

The authors concluded that screening for OSA could be age specific given the different risk factors present at the different ages. Also, the cutoff values for OSA may need to be altered given the child's age - using a more liberal cutoff for younger children and a more conservative one for older children. This is already being done at many sleep centers, where the sleep physician can use adult criteria or pediatric criteria cutoff values for children aged 13 and older.

Wednesday, January 7, 2015

Flying with your CPAP

I get asked about this regularly by my patients. This article is about traveling with a CPAP. Since using CPAP therapy with all sleep will maximize effectiveness, you should bring your CPAP with you when you travel. Of course, don't forget to bring all of the accessories, especially the power cord. Most CPAP machines these days come with a canvas bag to carry the device. I advise my patients to carry the device on board, not checking it as luggage. This is because the CPAP may be damaged during luggage handling or transportation in the plane, or your luggage may be lost. You will need to show the TSA agent the CPAP equipment. Nowadays, they will be used to it, and you will see many other travelers with their CPAPs. You may also need to bring a letter from your physician or a specialized luggage tag that says the CPAP is a medical device that has been prescribed for you.

Some travelers, especially on overnight flights, will want to use their CPAP's on the plane. You will need to check with the airline to see if their planes have power sources and if you can sit near enough to one to plug in your CPAP. Be sure to ask what kind of power source the plane has, as you may need an adapter. Some of my patients have gotten small travel CPAPs that operate on battery power.

If you use the humidifier chamber, don't try to bring distilled water on the plane. Best to buy it at your destination, if available.