An interesting study in the American Journal of Clinical Nutrition about sleep deprivation and calorie consumption. Thirty men and women in their 30's and 40's, all of about normal weight, lived and slept in a research center during 2 different 5-night periods. During one of the visits, participants were allowed to sleep 9 hours each night. During the other 5-night visit, the participants were only allowed to sleep 4 hours per night. During both 5-night periods, they were fed strict diets for the first four days, then allowed to eat whatever they wanted on the fifth day.

The results showed that regardless of the sleep schedule they were on, the participants burned a similar amount of calories, about 2600 calories per day. In those that slept only four hours, they fed themselves about 300 more calories on average on that final day than when they slept 9 hours.

The researchers propose that sleep is involved in how your body manages hormones that are involved in hunger and food choices when you're hungry. The difference between 9 and 4 hours is dramatic, and I wonder if people would eat more calories if they got 5, 6, 7, or 8 hours of sleep? More studies are needed to answer this and other questions about the relationsip between sleep, sleep deprivation, and obesity.

A New Way to Control Pressure in CPAP for Obstructive Sleep Apnea

In the June edition of the Journal of Clinical Sleep Medicine is an article about Fisher & Paykel's SensAwake system. The authors describe how long-term compliance with CPAP varies from 29 to 83%. One of the factors that affects usage is perception of excessive pressure. Many of the new CPAPs have a comfort feature that allows the user to ramp the pressure up from the lowest setting to the prescribed pressure over a certain number of minutes. If a patient wakes in the middle of night, however, they would have to reach over and activate the CPAP ramp again. The SensAwake system allows the CPAP machine to evaluate the breathing patterns of a CPAP user while it is being worn. If the SensAwake CPAP detects a breathing pattern characteristic of being awake, then it automatically lowers the pressure. This will prevent the patient from having to lower the pressure with the ramp manually. The SensAwake will then automatically increase the pressure once it detects breathing patterns consistent with sleep. Thus, SensAwake might reduce the time a patient is awake at night with the CPAP on.

The hope is that the SensAwake will make the CPAP pressure more comfortable (and possibly lower) if and when the user wakes up in the middle of the night. In the study, 42 patients were randomly selected to wear either a regular CPAP or one with SensAwake for the first night in the lab. On the second night in the lab, the patient wore the other type of CPAP. The results showed that there was no difference in the amount of time patients spent awake at night, no difference in the stages of their sleep, and no difference in the patients' perception of therapy between the regular CPAP and the SensAwake one.

These results are not surprising. In my experience, when the overwhelming majority of patients wake in the middle of the night with their CPAP on, they do not complain of the pressure being too high - they report that they can't even tell if the CPAP is on because they have acclimated to the pressure while asleep. Also, a significant amount of patients don't like the ramp feature after they have worn a CPAP for several weeks. So I imagine the SensAwake feature might disturb those patients as well, since it automatically activates the ramp feature.

To be fair to the SensAwake system, this study only measured one night's effects. We need long-term studies to determine its effect on long-term compliance.

Insomnia, Western Medicine, and India

I saw an article in Reuters Health about drug companies pushing western medications in countries like Inida. The article was in reference to a newspaper ad published in India by the pharmaceutical company Abbott. The ad does not mention the drug Abbott makes, but uses a research finding to draw attention to insomnia by "scaring" consumers.

The ad says "research shows that sleeping less than 6 hours per night leads to a 48% increase in developing or dying from heart disease." This research is from a real study, but the underlying message implies that sleeping 6 or more hours will protect from heart disease - which is not necessarily true. There is a link on the ad to a website featuring Abbott's insomnia drug, Zolfresh, which is the same as Ambien. The concern is that this ad will drive demand for insomnia medications, with Indian consumers thinking they may protect their heart if they take a sleeping pill. This isn't necessarily true, as there are several studies showing an increased mortality rate for those taking sleeping pills, even when controlling for other medical diseases.

Apparently, incomes are rising, insurance coverage is expanding, and there is more chronic disease among people of India. This translates into a large, untapped market for pharmaceutical companies. The companies say they are raising awareness of disease and illness by running these ads - perhaps they are. However, on the ad in question, there is no mention of behavioral treatment for insomnia - which would be the preferred treatment modality by most sleep physicians. There are 10 questions that consumers can answer about their sleep. If they answer positive to just one of those, the ad suggests you talk to your doctor. I guess that's a good thing, as long as that doctor is able to do a thorough sleep assessment or refer those patients to sleep physicians.

Nasal Masks vs. Full-Face Masks During CPAP Titrations

In the July edition of the Sleep Journal is an article about using different types of CPAP masks during CPAP calibration studies. Currently most patients with suspected obstructive sleep apnea (OSA) have the diagnosis confirmed by a sleep study. If that patient will be using CPAP for treatment, than usually the patient spends a second night in the sleep lab to have the CPAP calibrated (or titrated) to the optimal settings while the patient is asleep. During this titration study, the mask(s) used can make a big difference. But, as the study authors point out, there are few studies done to help sleep technologists decide which type of mask to use on the titration study - over the nose (nasal) or over the nose and mouth (FFM) mask.

In this study, researchers randomly assigned 24 patients with OSA to two separate titration nights - one with the nasal mask and the other with the FFM. For the nasal mask titrations, the researchers had the patient wear a chin strap to keep the patient's mouth from opening which would prevent mouth leak. These patients were titrated using "smart" CPAP machines in the lab, which are capable of finding the optimal pressure settings automatically. In other words, these patients' CPAP's were not calibrated manually, as is the standard. This was on purpose to minimize human variability. The final pressure determination though was chosen by a sleep physician after they reviewed the titration study.

The results showed that the optimal pressure chosen by the sleep physician was no different for the nasal vs the FFM. Also, the automatic CPAP chose similar pressures whether it was a nasal or FFM. Fifty-four percent of patients had pressure differences that were less than 2 cm whereas 46% had pressure differences of 2 cm or greater between the two mask types.

Patients also rated nasal masks as better fitting and more comfortable than FFM, which has been my clinical experience. Perceived sleep quality was not different for the nasal mask vs FFM. Titrations done with the FFM, compared to the nasal mask, did have increased mask leak, more mouth dryness, increased residual respiratory disturbance and arousal indexes, decreased slow wave sleep, and decreased total amount of total sleep time on the titration night.

The results of this study support using nasal masks rather than FFM for titration studies. This has been my experience as well. Sometimes, sleep technologists have to use a FFM because the patient has persistent mouth leak on a nasal mask, even with the chin strap. Using the best type of mask may improve CPAP compliance as patients early experiences with CPAP tend to predict long-term usage.

Sleep-Disordered Breathing and Polycystic Ovarian Syndrome

An interesting abstract in the Journal of Pediatrics about polycystic ovarian syndrome (PCOS). PCOS is an endocrine disorder that affects the ovaries and produces menstrual abnormalities, excess male hormones, and elevated weight. Since many girls with PCOS are overweight, they are at increased risk of sleep-disordered breathing (SDB) like obstructive sleep apnea, excessive daytime sleepiness (EDS), and the metabolic syndrome.

Researchers studied 103 girls with PCOS and 90 controls, all ages 13-18 years old. Both groups were matched by age, ethnicity, and body mass index (BMI). The results showed that SDB occurred in 46% of the girls with PCOS versus 28% in controls. EDS occurred in 54% of girls with PCOS versus 36% of controls. The metabolic syndrome occured in 43% of girls with PCOS versus 16% of controls.

This means that girls with PCOS have a higher risk of having SDB and EDS than girls without PCOS, regardless of obesity. The researchers suggest that patients diagnosed with PCOS be referred to sleep physicians if they exhibit EDS or other sleep disturbances.

Better Sleep and Daytime Functioning When Parents Set Bedtimes in Adolescents

There is an interesting article in the June edition of the Sleep Journal about parents setting bedtimes for adolescents, and the impact this can have on sleep and daytime functioning. Many adolescents are sleep-deprived these days due to early school start times, need to complete homework, after school activities like work and sports, and of course, smart phones / TV / video games in the bedroom.

Researchers surveyed 385 adolescents aged 13-18 years old, and 17.5% of them said their parents set their bedtime. Naturally, this was an age dependent finding, with more younger children reporting parent-set bedtimes than older children. But the interesting part was that those children that had parent-set bedtimes went to bed 23 minutes earlier, slept 19 minutes more on school nights, reported less datyime fatigue, and had less trouble staying awake during the day. There was no difference in the reported time it took to fall asleep, whether the parent or adolescent set the bedtime.

The researchers concluded that the findings from this study support the potential benefit of parent limit-setting around bedtimes for adolescents. Of note, the differences in sleep parameters disappeared on the weekends, when parents did not set bedtimes for the adolescents. This further strengthens the positive effect that the parent-set bedtimes had on sleep.

Possible Mechanisms of Central Apneas in Obstructive Sleep Apnea Syndrome

An article in the June edition of the Sleep Journal is about the different types of apneas seen in patients with obstructive sleep apnea syndrome (OSA). This post is going to be on the technical side, so reader beware. There are two main types of apneas. Obstructive ones are the more common type, and occur when the upper airway (or throat) collapse. Central apneas occur when the throat remains open, but there is no breath due to a communication problem between the brain and lungs. An analogy might help explain it better. Imagine our respiratory system is like a garden hose attached to a spigot. If you turn the spigot on, but pinch off the hose, you get little or no water flow - that is like an obstructive apnea. If you turn off the spigot, but leave the hose alone, you get no water flow - that is like a central apnea.

In OSA, patients usually have mostly obstructive apneas, but can occasionally have central ones as well. Researchers are not clear why this occurs. There is speculation that in patients with both types of apneas, there are at least two mechanisms in place. One is that the throats of these patients collapse more easily than individuals without OSA - this leads to the obstructive apneas. The second is that there is an instability in the control of breathing in patients with OSA. What this means is that the brain likes to have a precise level of carbon dioxide (CO2) in the blood - if it gets too high, your brain will make you breathe harder and faster to bring down the CO2 level. If the CO2 level gets too low, your brain makes you breathe less or even not at all to allow the CO2 level to rise up to normal. If you have an obstructive apnea, your lungs are still trying to breathe, but can't due to the closed throat. After the obstructive apnea is over, however, some people's brain overcompensates and breathes too hard and too fast. This reduces the CO2 level and the brain reduces breathing rates to make the CO2 level rise - this compensation can lead to the central apneas seen in OSA.

In this study, researchers studied the differences between patients with OSA that had pure obstructive apneas and no central apneas, and those with predominant obstructive apneas but with some degree of central apneas. Using sophisticated tools, they determined that patients with predominant OSA had more respiratory control instability than those that had pure OSA. In other words, the patients with predominant OSA were more likely to have their spigots turned off. Both groups had the same upper airway collapsibility, so that does not explain why the predominent OSA group has central apneas. These findings could help researchers figure out ways to treat patients that have non-obstructive apneas as part of their OSA syndrome.

Air Leak and Adherence to Auto-titrating CPAP

In the June edition of the Sleep Journal is an article about the association of air leak and adherence to auto-titrating continuous positive airway pressure (APAP). Before we get to the study, let me explain about APAPs.

Normally, a patient that is suspected to have obstructive sleep apnea (OSA) has an overnight sleep study in the sleep lab. After that, the patient will have to spend another night in the sleep lab to calibrate the CPAP to determine the appropriate settings.

Some sleep centers and other physicians have attempted to shorten the above process. Some use home sleep studies (a separate topic altogether) to make the diagnosis. Instead of a CPAP titration study, they will send the patient home with an APAP that is able to automatically calibrate itself while the patient sleeps at home. Usually this is done for a week or two, then the APAP and patient come back to the clinic where the APAP data is downloaded. The physician can then set the APAP to a fixed, unchangeable pressure that hopefully corresponds to what the pressure would be had the patient been calibrated in the sleep lab initially.

In the current study, researchers set up 96 patients with such a model. Home study / questionnaire diagnosis of OSA followed by a week of APAP and then 5 more weeks of straight CPAP. These patients were not diagnosed or calibrated in a sleep lab. The researchers were interested in the association of air leaks in the APAP systems and APAP compliance. The results showed that larger air leaks during APAP therapy was associated with poor adherence compared to smaller air leaks. The researchers speculated why air leaking might reduce adherence. If the air leak was because of mouth opening, this could cause mouth / throat dryness, which then could decrease compliance. Also, the APAP might not perform as well with a leak in the system, as normally APAP is a closed system under pressure. If the APAP can not respond to the OSA as easily because of the leak, then the APAP might not have been as effective and this could reduce adherence.

One thing the researchers did not mention is the noise level that occurs when the APAP leaks. Normally, an APAP that is not leaking is whisper quiet. But the air leaks can be quite loud, disturbing the patient and a bedpartner. This could lead to reduced compliance.

Sleep Duration and Obesity in Children

This post is about a study on childhood sleep duration and obesity in the British Medical Journal. There is alot of interest in determining whether sleep deprivation contributes to obesity in children and adults. Other studies have shown a link, and I have posted about it.

In this study, researchers took annual measurements of children as they aged from 3 to 7 years old. Sleep was measured at home with an actigraph, a form of home sleep study. The children wore the actigraph for 5 consecutive nights at ages 3, 4, and 5 years of age. Dietary intake was assessed over three days at ages 3, 4, and 5 years. It's not clear why sleep and dietary data were not collected for ages 6 and 7. Other data were collected about the children and their families.

The results showed that BMI tended to decrease slightly with age, and the average BMI was not elevated in the children. Average BMI's varied from 16.5 to 17.1, with overweight being defined as BMI 25-30. Data about the average fat mass index was not provided for unclear reasons. The sleep durations, as measured by the actigraph, were very similar across the three age ranges - 3 year olds averaged 11.1 hours per night, 4 year olds averaged 11.0 hours per night, and 5 year olds averaged 11.1 hours per night of sleep.

Stopping right there, and freely admitting I am not a statistician, these numbers seem pretty similar with regard to BMI and sleep duration. However, when the numbers were crunched by the researchers, they concluded that children who sleep less (at ages 3 - 5 years old) have a significantly higher risk of having a higher BMI at age seven, even after adjustments for other risk factors that have been implicated in regulation of body weight. In fact, each additional hour of sleep per night at ages 3 to 5 is associated with a reduction in BMI of 0.49 at age 7. The researchers and I agree that this is a pretty small effect when applied at the individual level. The researchers state that this small difference could become important for public health, when the data are applied to population levels. Also, the differences in BMI were more commonly due to an increase deposition of fat mass, rather than an accumulation of fat free mass (muscle or bone, eg).

This study did not examine the underlying reasons why shorter sleep durations might contribute to obesity. It could be due to hormonal, dietary, or behavioral factors.

Nasal Steroid Sprays and Pediatric Obstructive Sleep Apnea

Medscape has a review of a study in the June issue of the Archives of Otolaryngology - Head & Neck Surgery about how nasal steroid sprays may improve obstructive sleep apnea (OSA) in children.

Researchers compared the amount of an inflammatory cytokine called interleukin-6 (IL-6) in adenoids removed from children who were treated with a nasal steroid spray to controls who did not receive any nasal spray. The results showed that the adenoid cells released less IL-6 in those children who received the nasal steroid spray. The authors think that reducing IL-6 levels could reduce inflammation in the nasopharynx, which could improve nasal airflow, and consequently improve OSA.

These results are exciting because it could mean that treating nasal airway inflammation with a nasal spray might be an alternative to surgery in treating mild OSA in children.

FAA and Air Traffic Controller Fatige

I saw in the LA Times that the FAA has announced new rules to prevent air traffic controllers from falling asleep on the job. Currently, air traffic controllers caught sleeping on the job, even if on break, can be fired because the agency says that the controllers need to be available for recall at all times. Since April, the FAA said there has been 7 instances of controllers sleeping on the job and 2 others where the controllers did not respond to attempts to contact them.

So the FAA's new plan is that controllers who are sleepy can listen to the radio or read to stay alert during overnight shifts when air traffic is light. The ruling still does not allow the controllers to take naps, even though that would be the most effective way to improve alertness. This makes no sense - if I'm sleepy, reading is probably not going to keep me alert. Physical exercise, napping, and perhaps some caffeine might, but not the radio or reading. I wonder if the American Academy of Sleep Medicine will get involved in this, to help guide the FAA in their attempts to combat controller fatigue.

Sleep Extension and Athletic Performance

There is a fascinating article in the July edition of the Sleep Journal about how sleeping longer can improve athletic performance. Sleep researchers have documented how sleep deprivation can negatively impact cognitive performance like memory and reaction time as well as mood. Some sleep deprivation studies have even shown that sleep loss can impair weight-lifting and cardiopulmonary functioning. However, there have been few studies about the effect of sleeping longer on athletic performance. The authors of this study believe that the vast majority of college students, especially athletes, suffer from chronic sleep deprivation due to academic, athletic, and social demands on their time - and this sleep debt could impact athletic performance.

In this study, the 11 subjects were college basketball players at Stanford University. They kept their normal sleep times of 6-9 hours per night for 2-4 weeks at baseline. Researchers than had them extend their sleep duration to a minimum of 10 hours of sleep per night for 5-7 weeks. While traveling, participants were allowed to nap during the daytime if their schedule did not allow them to sleep the full 10 hours at night. The sleep extension aspect occurred during the regular basketball season.

Sleep times were measured subjectively by sleep diaries and objectively by a home sleep monitor worn on the wrist. Athletic performance was measured by a timed sprint and free throw and 3 point accuracy. All performance measures were performed after each regular practice session in the late afternoon. Reaction time was also measured twice daily by a hand-held computer device. Daytime sleepines and mood were recorded with subjective questionnaires.

The results showed that the players increased objective sleep time by 111 minutes during the sleep extension time period. Reaction time improved significantly during the sleep extension portion compared to the baseline. Daytime sleepiness went from a level that is considered borderline sleepy to completely normal during the sleep extension. Mood, self-perception, and subjective performance during practices and games all improved with sleep extension.

The authors pointed out that the athletes were able to fulfill their typical personal, work, and training obligations while also extending their total sleep time, meaning that sleep extension is a realstic option to improve performance. Also, the authors felt that the athletic performance measures (sprint time and shooting accuracy) got better from more sleep, rather than more practice, because they chose performance measures that were very familiar to the athletes and who had become quite proficient at them prior to the onset of the study. The authors did point out that this was a small study with no matched controls.

In conclusion, the results of this study demonstrate that increased sleep durations in college athletes can significantly improve athletic performance, overall well-being, and mental performance. Since the mental aspect to training and competition is so important, the results of this study are even more impressive. Perhaps more sleep will become an integral factor along with nutrition, conditioning, and coaching in enhancing athletic peformance.

Impaired Driving Simulator Performance in Treated Obstructive Sleep Apnea

Another interesting article in the June edition of the Journal of Clinical Sleep medicine about driving simulator performance. Studies have shown that untreated obstructive sleep apnea (OSA) impairs driving performance. Studies have also shown that treating OSA with continuous positive airway pressure (CPAP) improves driving simulator performance and reduces accident risk. However, these studies have some methodological limitations, such as driving simulator programs that are too short (less than 20 minutes, for example). Finally, other studies have shown that CPAP treatment may only be partially effective at restoring cognitive function, cortical activation, and daytime sleepiness, meaning that even treated OSA patients could have persistent, impaired driving performance.

The researchers studied patients with severe OSA and healthy controls to see if 3 months of CPAP therapy could improve driving performance in simulators of 90 minutes, similar to a long, country drive. The results showed that patients with untreated severe OSA had impaired driving simulator performance compared to matched controls. And 3 months of CPAP therapy did improve performance, but not to the same level as matched controls. This means that despite adequate treatment for OSA, these patients could be at increased risk for driving accidents compared to drivers without OSA.

As this study was small, it will be interesting to see it repeated in a larger population, as the public health implications could be dramatic.

Truck Drivers and Online Assessment of Obstructive Sleep Apnea

A study done in the June edition of the Journal of Clinical Sleep Medicine describes data from an online self-assessment of obstructive sleep apnea (OSA) done by truck drivers anonymously. Some estimates say that OSA occurs in 1 in 4 commercial drivers. I blogged about this in May.

This study was a web-based survey of the Berlin Questionnaire, a valid screening tool used to assess risk of OSA. The Berlin has three sections - sleepiness, snoring, and body-mass index (BMI) and high blood pressure (HTN). If the Berlin was positive (indicating elevated risk of OSA), the driver was provided a link to a local sleep center for further evaluation.

The results of the survey showed that ~56% of respondents were positive on the Berlin and that 78% were positive on the BMI / HTN section. Seventy percent were obese, defined as a BMI >30. Witnessed apneas were reported in 21% of responders and almost 21% admitted to falling asleep while driving!

The results stress the importance of testing and treating commercial drivers. How to identify those drivers at risk is still being debated. Hopefully we will have some guidelines from the Federal Motor Carrier Safety Administration at the end of this summer.