Common swift stays airborne for 10 months straight!

I know this article about birds isn't relative to human sleep (at least directly). I thought it was fascinating because as a sleep doctor, my first question was when do these birds sleep, if they can stay in the air for 10 months. All animals have to sleep, so they much be getting some sleep. Turns out they climb really high and then coast down for 30 minutes at least twice a day, presumably to take power naps. Scientists don't know for sure if the birds are actually sleeping, but this is their best guess, and it makes sense to me. Maybe the ornithologists need to do a portable sleep study on these birds!

American Academy of Pediatrics Updates

Recently, the American Academy of Pediatrics released updated guidelines on two important issues related sleep. The first update concerned sudden infant death syndrome (SIDS). Here is a link to the guidelines.

The second update concerned media use in children and adolescents. The recommendations discuss sleep and other aspects of how media affects children. For younger children, here is the link. For older children and adolescents, here is the link.

High blood pressure medications and obstructive sleep apnea severity

Obstructive sleep apnea (OSA) is associated with high blood pressure (HTN). Studies have shown that OSA is independently associated with resistant HTN and it is believed that untreated OSA may worsen HTN. However, studies involving treatment of OSA with continuous positive airway pressure (CPAP) have demonstrated only modest improvement in daytime blood pressure in randomized control trials. some research first speculate that the relationship between OSA and HTN may be bidirectional.

With OSA, the muscles that make up the throat lose their home causing collapse of that area and reduction in airflow to the lungs. Research her as hypothesized that intensive blood pressure control may influence always say I stabilizing the upper airway. There is also evidence for the role of volume status affecting the severity of OSA. What this means is that some people have worse OSA when they have too much blood volume from conditions like heart failure or kidney failure.

This study theorized that it is at least plausible that intensive treatment of HTN may bring about improvement in the severity of OSA, either by volume control, stabilization of upper airway muscles, or perhaps because of some direct effect of blood pressure medications. The researchers conducted a systematic review and meta-analysis on this topic.

Although there were limited number of studies and the studies were not of high quality, though results revealed that there was a decrease in OSA severity after treatment with blood pressure medications. Of note, the decrease reached statistical significance but the researchers doubted if it would be clinically significant.

I wanted to blog about this study in part because because throughout my career as a sleep physician I have thought of the OSA-HTN relationship as more one way, with OSA contributing to HTN, rather than the opposite as suggested by the authors of this study. Certainly more studies will be required before any definitive conclusions can be made.

Snoring and obstructive sleep apnea

Snoring is a common problem among men and women and is one of the cardinal symptoms of obstructive sleep apnea (OSA). With the explosion of smartphones and the emphasis on in-home monitoring, sleep researchers have attempted to use measurement of snoring to determine risk of obstructive sleep apnea. It has been difficult to do this because not all people who snore have obstructive sleep apnea. In addition, sleep researchers don't agree on an objective definition of snoring or an established threshold level of loudness. The quality of snoring is determined by multiple factors including the stage of sleep, body position, use of alcohol or other sedating medications, and upper respiratory tract illnesses such as a cold. There is significant variation of snoring from night to night for no apparent reason as well. Finally, snoring can be chronic throughout the night or periodic meaning that there are periods of silence between snoring episodes. The periodic snoring may be more suggestive of obstructive sleep apnea.

This study evaluated the diagnostic value of periodic snoring sounds measured during home sleep apnea testing. Subjects that were at risk for obstructive sleep apnea were sent home with a home sleep study monitoring kit and worn while they slept. The home sleep study kit has a built-in microphone that is located on the chest to detect the snoring sounds. the results showed a strong positive correlation between the percentage of periodic snoring and obstructive sleep apnea severity (AHI). The correlation was strongest for younger subjects, females, and obese subjects. The researchers discussed that some women do not get evaluated for obstructive sleep apnea because they do not know that they snore or are embarrassed to report snoring. In my clinic, I find this to be the case as well. Therefore measuring snoring at home while the patient is asleep many help sleep physicians to recommend formal diagnostic sleep studies to accurately assess female patients without a strong history of snoring.

Sleep restriction and athletic performance

I used to run long distance back in my salad (younger) days. I read books and magazines about running and running performance. I remember reading something back in the 1980's about how sleep deprivation did not affect running performance.

However, here is an article about recent research showing small reductions in performance of elite cyclists with voluntary sleep restriction to 4 hours per night for 3 days. The researchers measured energy expenditure, maximal aerobic power, and time to exhaustion. However, I don't see any data about actual cycling performance such as time to complete a course, etc. Therefore, I am not sure if sleep restriction really impacts elite cyclists. I know that not getting enough sleep lowered my motivation to run the next day!

High blood pressure and insomnia

Insomnia refers to an inability to sleep the desired amount despite adequate allotted time in bed. People with insomnia often misperceive their sleep duration. Research studies have linked chronic insomnia with increased risk of high blood pressure (HTN). Sleeping less than 6 hours is considered being a "short sleeper" and is also associated with HTN.

This study looked at the association between short sleepers with insomnia and HTN. Participants underwent two consecutive in-lab sleep studies to objectively monitor sleep duration. They also had the participants record their subjective sleep duration with a sleep diary. Results showed that insomnia with objectively-measured sleep duration less than 6 hours was associated with increased risk (Odds Ratio 3.59) for HTN. This finding was independent of the following confounders: age, gender, race, body-mass index, frequency of sleep aid use, sleep apnea severity, daytime sleepiness, diabetes, high cholesterol, depression, alcohol use, tobacco use, or caffeine consumption.

The authors concluded that the results provide further support for measuring sleep duration objectively, rather than subjectively for those patients with chronic insomnia. This means the authors are advocating for sleep studies in the evaluation of chronic insomnia to help determine morbidity risks associated with the insomnia.

Sleep duration and sleep hygiene differences in homeschooled vs public / private school students

Adolescents tend to be a sleep-deprived bunch. I know I was when I was in high school. Adolescents tend to stay up late, in part because of a biological shift in circadian rhythm. Plus, high school starts earliest, which deprives adolescents of sleep as well. On the weekends, some adolescents try to make up for lost sleep by sleeping in, but this does not erase 5 days of partial sleep deprivation. Advocates have requested later school start times to help, but this is not done in most schools.

This study is about kids that are homeschooled. In this population, these kids can sleep in later, offsetting the daytime sleepiness from sleep deprivation as seen in public / private school kids. Also, kids that are homeschooled have a parent with them more often and thus may have better sleep hygiene than public / private school kids - meaning less TV / screen time in bed, less caffeine in evening, etc.

Study participants were surveyed about their sleep patterns and sleep hygiene via internet. Mean age of the sample was 13.6 years old. The results showed that kids in public / private school went to bed somewhat earlier on weekdays, but got up much earlier, resulting in 49 less minutes of sleep than homeschooled kids. Also, public/private school kids tended to sleep in more on weekends than homeschooled children. Using the National Sleep Foundation’s categories of “optimal sleep” (>9 hours) 28.2% of public/private school students obtained optimal sleep on weekday nights compared to 58.0% of homeschooled students. Public/private school kids tended to have "poorer" sleep hygiene than homeschooled kids.

The authors concluded that later school start times would allow private / public school kids to get more sleep.

Nap duration and sleep inertia

Napping can help shift workers maintain alertness, but a nap that is too long can result in what's called 'sleep inertia'-the brief period of time of reduced alertness and impaired cognitive performance experienced immediately after waking from the nap. Minimizing sleep inertia may improve a worker's performance on the job. Some studies have shown that a 10 minute nap results in less sleep inertia than a 30 minute nap, possibly because the napper wakes from a lighter stage of sleep during the 10 minute nap. With a 30 minute nap, the napper is more likely to wake from slow wave sleep, which is the deepest level of sleep.

Relatively few studies on sleep inertia have been done where the night shift worker takes a nap during their work shift. This study examined the cognitive performance and subjective sleepiness immediately following either a 10-minute or 30-minute nap at 4 am. The researchers studied young, healthy volunteers in a research lab. Participants slept normally for the first night. The second night they were kept awake the entire night. One third were allowed no nap, another third were allowed the 10 minute nap, and the remaining third allowed the 30 minute nap. The participants did a battery of cognitive performance tests and subjective rating scales prior to the nap and 4 times during the first hour after the nap.

Remembering this is a small study, the results showed that 8/10 participants woke up in a lighter stage of sleep after a 10 minute nap. Also, 8/10 participants woke from slow wave sleep after the 30 minute nap. 3/10 participants entered into slow wave sleep in the 10 minute nap compared to 10/10 participants in the 30 minute nap. In other words, the longer nap allowed enough time for the participants to progress to the deepest level of sleep.

Regarding the post-nap testing, the 10 minute nap was associated with minimal sleep inertia and was helpful in slowing the performance decline seen in the group that took no nap at all. The 30 minute nap was associated with substantial sleep inertia. In addition, even though there was objective proof of reduced cognitive performance following the 30 minute nap, those participants rated their sleepiness as better after the longer nap. This means that the participant who napped 30 minutes overstated their ability to perform cognitive tasks during the hour following that nap. The study authors suggest that if night shift workers have to perform immediately post-nap, that the worker take only a 10 minute nap rather than a longer nap.

Sleep deprivation and false convictions

Here is a study that attempted to link sleep deprivation to "false confessions." I don't have access to the entire study, only the summary article referenced above. Researchers studied 88 participants in a research lab, where some were sleep deprived for 24 hours and others slept 8 hours. The researchers had the participants take a series of computerized tests and were told not to press the 'Esc' key as that would delete data. At the end of the study, the participants were asked to sign a statement stating they had pressed the 'Esc' key. Results showed that 50% of the sleep-deprived people vs only 18% of the well-rested people signed the 'false confession.'

I'm not sure this demonstrates that sleep-deprivation leads to more false confessions. It may be that sleep-deprivation causes individuals to pay less attention to what they are reading. Signing something at the end of a research study has far less implications than signing a confession statement where you are being accused of a crime you didn't commit. In the latter instances, adrenaline may offset the affects of any sleep deprivation.

Bedtime and metabolic health

Research has shown an association between shift work and metabolic health. Specifically, shift workers are prone to obesity and type 2 diabetes. However, there is less research data about a variable sleep schedule that is not related to shift work. I'm referring to individuals who have one bedtime during the work week but a later bedtime on the weekends. This study researched the effects of going to bed later on weekends and obesity as well as metabolic health. They studied all women with a mean age of 52 years. The researchers collected information annually on sleep times and duration with a sleep diary for about 5 years. They recorded the patient's weight and drew blood to check for insulin resistance (a marker for pre-diabetes). The results showed that a greater variability in bedtime and going to bed early was associated with an elevated body mass index. Interestingly, the mean bedtime and going to bed later were not related to body mass index. However, variability in bedtime and going to bed later on the weekends was associated with an increased rate of insulin resistance, even after adjusting for factors including sleep duration.

The authors speculate on the reason why later weekend bedtimes could contribute to insulin resistance. One possibility is that there is more exposure to light at night which could alter melatonin and possibly increased consumption of food. However there was no significant increase in weight over time despite later bedtime. It may be that people who go to bed later on weekends are eating more simple carbs but don't necessarily gain weight. Increased carb intake could be contributing to the insulin resistance. More studies will need to be done to see how clinically important these effects are, as the statistical differences were real, but small.

UNM hospital room lighting

Light affects sleep - especially our circadian rhythm, or the timing of our sleep. The University of New Mexico has built a hospital room with special lighting equipment that researchers will be able use to study the circadian rhythm of humans. The researchers will also be able to study how light effects certain neurological and psychiatric disorders such as delirium after surgery, depression, dementia, and psychosis that develops in ICU patients. Apparently, the lighting is "smart" in that it can alert a nurse that a patient has fallen, but the lighting uses no cameras! Not sure how that works, but it sounds pretty cool to me.

Importance of sleep

This article discusses a survey of Americans and New Years resolutions. I don't have access to the study, only the article that describes it. The article says that more half of respondents prefer a resolution of more sleep than going to the gym. Seems fairly obvious to me. Exercising is hard, but sleeping (usually) isn't. The article goes on to detail how sleep is viewed as important to many Americans. Again, fairly obvious responses. Since we all have to sleep, and we do it for about one-third of our life, it's going to be pretty important to humans. Right up there with eating, drinking, and shelter.

Sleep and attention

This article discusses research in animals regarding the "yin and yang" of sleep and our ability to pay attention when awake. Probably seems fairly obvious to most of you, but it's interesting to see research findings supporting our clinical knowledge.

Fiber and saturated fat are associated with lighter sleep

Research studies have shown that reduced sleep amounts can impact food intake and weight. However there is relatively little information on how food intake could impact sleep. Apparently much of the work has focused on self-reported diet and self-reported sleep - in other words, not much has been done in a controlled, monitored environment.

This study attempted to assess whether sleep patterns were different after periods of controlled feeding versus ad libitum feeding - this means that one group was given exactly the same food. The other group was given $25 to buy whatever food they wanted. The controlled feeding was on days 1-4 and the ad libitum feeding on days 5 and 6. The participants sleep was monitored each night with a sleep study.

The results showed that ad libitum food intake was associated with a decrease in slow-wave (the deepest level) sleep and an increase in the time it takes to fall sleep. The greater intake of saturated fats and a lower intake of fiber were also associated with less deep sleep. Additionally increased intake of both sugar and non-sugar/non-fiber carbohydrates was associated with more arousals during sleep. The authors speculate whether a diet rich in fiber with reduced intake of sugars and other non-fiber carbohydrates maybe as useful tool to improve sleep depth and architecture in individuals with poor sleep.

These results are interesting, but the actual data shows what I consider to be small effects. The decrease in slow-wave sleep went from 29.3 minutes to 24.6 minutes per night. This may be statistically significant, but I wonder if this is really clinically significant. The time it took to fall asleep went from 16.9 minutes to 29.2 minutes - arguably a more noticeable change. Of note, there was no subjective evaluation of the patient's perceived sleep quality changes with the two different diets.

No link between wake up time and income

I hadn't given this topic too much thought before, but I did find this article somewhat interesting. This study is based on a survey of individuals' wake up time and annual income. The results showed that the wake up time was no different in the highest income earners vs the lowest earners. The article goes on to say that the results of this study do not support the notion that the early bird gets the worm. I'm not so sure as other factors are not being considered in this situation.