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.

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!

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.

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.

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.

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.

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.

Poor sleep quality and Alzheimer's disease

This article discussed research about Alzheimer's disease and sleep. Researchers looked at a marker for Alzheimer's, called beta-Amyloid. The results showed that those with lower sleep quality and shorter sleep duration had higher levels of beta-Amyloid. However, sleep duration and quality was determined by subject self-report. It will be helpful to see if the relationship holds up with objective sleep measurements.

Sleep not to blame for all fatigue

Many of my patients feel that fatigue is due to how long they sleep. In some cases it can be. But fatigue has many causes. This article discusses research showing no link between self reported sleep duration and fatigue. Unfortunately, certain sleep disorders may be occurring without the persons awareness, like obstructive sleep apnea (OSA). OSA can cause fatigue, and treatment of OSA can help. So before concluding that your fatigue is not related to your sleep quality, talk to your doctor.

Sleep duration may impact concussion test scores

In sports, concussions are a big deal. Trainers, doctors, and coaches need accurate information to determine if a player is ready to play again, or if the player needs to rest due to concussion. This study shows that sleep durations < 7 hours can worsen the tests used for concussion, even when the player has no concussion. This means that players should be getting as much sleep as possible, especially the night before the concussion testing, to make the testing as accurate at possible.

Sleep duration and adolescent obesity

Another story about sleep duration and obesity. This study looked at 1390 kids from age 14 to 18 years old. They asked them to report their height, weight, number of hours they sleep per night, physical activity level, and amount of time spent in front of a screen (TV / video games / computer) every 6 months. The average amount of sleep per day was about 8 hours and this decreased to 7.5 hours by the time the kids reached age 18. When the researchers crunched the numbers, they saw that longer sleep duration was associated with a lower body mass index (BMI), a ratio of height to weight. The higher the BMI, the more overweight the kid. The association between BMI and sleep duration was stronger as the BMI increased - for each additional hour of sleep past 8 hours, the BMI was lower than the average. This means that more sleep seemed to help the most overweight kids.

From these results, the authors suggest that kids who sleep at least 10 hours per day could reduce their BMI. Interestingly, the association between BMI and sleep duration persisted even when accounting for physical activity and screen time. So even if overweight kids watch TV as much as normal weight kids, increased sleep duration may reduce obesity.

One important limitation in this study is that they did not monitor calorie consumption. So, like I've mentioned in other posts, longer sleep may be associated with less weight because of decreased calorie consumption, not from longer sleep itself.

The authors point out that telling kids to sleep more does not work. But delaying school start time in the morning may allow kids to sleep more. Also, getting all electronic devices out of the bedroom at night may increase sleep duration.

Home schooled teens get more sleep

There has been much criticism of school start times. Elementary school children start the latest and high school students start the earliest. But this goes against our sleep biology - young children get up earliest and teenagers sleep later. Here is a study showing that home schooled teens get about 1.5 hours more sleep per night than those students in public or private schools. In fact 55% of home schooled teens got enough sleep versus 25% of public / private school teens.

TV before bedtime can reduce kids sleep duration

This article discusses research showing that increased TV time before bed can reduce total amount of sleep time in children. The study is based on a survey, so has biases but still points to some commonsense things parents need to remember about their children's bedtime rituals. Limiting screen time, especially around bedtime can help kids sleep better and longer. It's not just the content of the TV program that is the problem, but just the light from the screen itself can suppress melatonin.

More sleep at night can reduce sports-related injuries in teens

Here is an article about research showing that adolescents were less likely to get injured while playing sports if they got at least 8 hours of sleep.

Protected sleep time allows medical trainees to sleep more

In the last few years, the hours worked by medical interns and residents has come under scrutiny. Regulations have been put in place to limit the number of hours worked in an attempt to reduce patient errors. Here is an article about a study showing that if you give medical trainees 5 hour protected time to sleep while on call, they will sleep an extra hour on average. However, the researchers did not measure medical errors, so it's not clear if that extra hour of sleep made any significant difference.

Kids do get recommend amounts of sleep

Lots of press about how kids are getting too little sleep. And lots of ink about how too little sleep contributes to childhood obesity. This article discusses new research showing that kids get as much sleep as recommended. Time to focus on the more likely problem of childhood obesity - diet.

Short sleep duration and breast cancer

This article discusses research showing an association between post-menopausal women with short sleep durations and aggressive breast cancer. There was no association between the aggressiveness of the cancer and sleep duration in pre-menopausal women. The researchers obtained sleep duration by asking the women how long they slept on average, and this method is not the most accurate. It's not clear why the link between short sleep duration and aggressiveness of breast cancer - it could be that insufficient sleep causes our bodies to be in a chronically inflamed state, which perhaps may be more advantageous for certain tumors. More studies are needed to see if better or more sleep could reduce the aggressiveness of breast and other cancers.

Sleep duration and response to Hepatitis B Vaccination

There has been a lot of press about this, so I thought I would review this article published this month in the Sleep Journal. The premise of the article is that sleep deprivation has been shown to affect the immune system. But this study set out to determine if sleep duration would predict if patients would respond to Hepatitis B vaccinations.

Researchers studied 125 healthy subjects aged 40-60 years old. They had the patients record sleep diaries and rated their sleep quality for 3 days before and after each of three Hep B vaccination injections. After the study was started, they did measure 104 patients sleep with a home sleep test, called an actigraph.

The researchers broke up sleep into three categories - less than 6 hours, 6-7 hours, and more than 7 hours. The results showed that the shorter the sleep duration, the lower the response to the vaccinations. The findings were independent of age, sex, and BMI, which apparently have beeen shown to affect vaccination response. Only sleep duration, not sleep quality or sleep efficiency, was correlated with vaccination response.

The researchers did not measure daytime sleepiness. So it is not known if the subjects who got 6 hours but were not sleepy also had a decreased immune response. In other words, this study does not tell us if sleep deprivation (needing 8 hours, but only getting 6 hours) or just getting 6 hours or less is associated with the decreased immune response. Some people are short sleepers, needing only 4-6 hours of sleep per night. Do they really have lowered immune response? My intuition is that sleep deprived individuals would have the lowered immune response, not short sleepers. Perhaps experiements should be done on those who sleep 8 hours, but need to sleep 10 hours. So it may not be the absolute number of hours of sleep, just the number of hours obtained relative to the number hours needed to feel rested.

Alcohol can Shorten Overall Amount of Sleep

Here is an article about how drinking alcohol close to bedtime can shorten the overall amount of time the drinkers slept. This is new information, as studies have only shown that alcohol disrupts sleep. This study was also unique in that it measured sleep over many nights in the participants' homes.