SciBlogs

World Sleep Day Karyn O'Keeffe Mar 14

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Every year on the third Friday of March is World Sleep Day – a day when we aim to educate others about the importance of sleep and promote ways of getting good, healthy sleep. Each year also has a theme, such as “good sleep, good aging”, “sleep well, grow healthy” and “drive alert, arrive safe”.

This year’s theme is “restful sleep, easy breathing, healthy body”.

Restful sleep = healthy body

Good sleep is about getting enough sleep, of good quality, at the right time of day.

So how much sleep do we need? Studies show that adults need about 7-9 hours sleep each night. Less than 7 hours sleep has immediate effects: poor decision making, less creativity, slow reaction times, poor motor function, poor mood, and increased relationship conflict. In the long term, it can lead to health problems, such as obesity, type 2 diabetes, high blood pressure and heart disease.

Good quality sleep is not just about the amount of sleep that we get, but also about the structure of our sleep. Our sleep should be made up of all of the sleep stages: light sleep, deep sleep and REM sleep. We should also have minimal awakenings overnight. Light and noise in the bedroom; caffeine, alcohol and nicotine in our system; and stressors in and out of the bedroom can lead to broken sleep, and in turn poor sleep structure.

We get the best sleep when we sleep at night. The timing of our sleep can be altered by not having regular bed and wake times, and by exposing ourselves to bright light in the evening.

  1. Block out light with good quality curtains. Turn off lamps at night.
  2. Turn off computer screens, TVs and radios in the bedroom. Turn off audio notifications on phones, tablets and computers. (Better still, place your phone and tablet on the kitchen bench so you’re not tempted to check it in the middle of the night.)
  3. Avoid caffeine in the 5-8 hours before bed. Keep alcohol intake to a moderate level and avoid alcohol in the 2-3 hours before bed.
  4. Reserve the bedroom for sleep and sex.  Avoid bringing work and recreational activities into bed with you.
  5. Dim the screens on electronic devices in the evening (computers, tablets, smartphones) and avoid using these devices in the 2 hours before bed.
  6. Avoid exposing yourself to bright light during the night. Check emails, Facebook and Twitter in the morning.
  7. Incorporate activities into your day that promote sleep, such as a regular bedtime routine and regular exercise in the late afternoon/early evening. (Avoid intense exercise in the 2-3 hours before bed.)

Easy breathing = restful sleep = healthy body

This year’s theme also focuses on breathing problems during sleep.  Obstructive sleep apnoea is a breathing disorder where individuals stop breathing multiple times overnight. It results from the tissue in the upper airway relaxing (collapsing) during sleep. Typically, each apnoeic event results in a drop in oxygen levels in the blood and an awakening from sleep. When someone stops breathing frequently overnight, their sleep can be non-restorative and their daytime functioning can be greatly impaired (see above about short sleep). Long term they have an increased risk of developing high blood pressure, heart disease, stroke, type 2 diabetes and obesity.

If you snore very loudly or someone you know tells you that you stop breathing overnight, have a chat with your GP about whether you might have obstructive sleep apnoea.

 

Sleep disorders in New Zealand teenagers Karyn O'Keeffe Dec 09

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Last week saw media reports stating that, alarmingly, almost 40% of New Zealand teenagers have a sleep disorder. This stemmed from a Royal New Zealand College of General Practitioners press release, and a paper published in the Journal of Primary Health Care. At face value, these findings are very concerning indeed.

The study surveyed 1388 Auckland high school students, from six different schools, using the authors’ Auckland Sleep Questionnaire. Drawing from the International Classification of Sleep Disorders, this questionnaire aims to assess a number of sleep problems commonly seen in primary care, and their potential underlying causes. An algorithm is then used to diagnose insomnia, obstructive sleep apnoea, parasomnias, delayed sleep phase disorder, medical problems, substance problems, and mood disorders.**

As an example, the criteria used to determine whether an individual has a sleep problem are outlined below. These are not unreasonable and for the most part describe the broad criteria used to diagnose insomnia.

Do you have problems getting to sleep, staying asleep or waking early such that it affects your work function the next day? This includes feeling excessively sleepy the next day for the duration of at least one month.

The study found that 37% of teenagers reported ‘significant sleep symptoms’ lasting more than a month. Depression and anxiety are cited as the main contributor of sleep problems in teenagers, and alcohol as a significant contributor. The relationships between depression and anxiety and sleep problems are well established, and modest correlations were observed here. However, unfortunately the authors have assumed causal relationships based on relatively high prevalence rates for alcohol use in this group of teenagers (or at least alcohol as an independent predictor is not reported).

There is no question that sleep among New Zealand teenagers is a significant concern. Large population studies of New Zealand teenagers have shown that approximately 21% of New Zealand teenagers do not get enough sleep (8-9 hours rather than the recommended 9-10). There is also a large discrepancy between bedtimes on school nights (10.30pm) compared with weekends (midnight). However, significant contributors to this are changes to the biological clock seen during adolescence, growing independence and the increasing use of light-emitting technology in the evening (I’ve blogged about this before).

If 37% of New Zealand teenagers have a sleep problem, where to from here? There is little New Zealand data from which to design strategies for improving sleep health in teenagers, and unfortunately this study does not advance our ability to do so. Taking into account other known contributors to sleep disturbance in adolescence may have provided greater understanding of the extent of some of the behavioural (and physiological) factors that can lead to sleep problems. These may have included sleep duration, which is a known risk factor for poor daytime functioning and parasomnias. Additionally, those with an irregular sleep schedule (and no sleep disorder) may have trouble getting to sleep when they want to. Teenagers who are required to wake early on school days may feel like they have to wake earlier than they would like and consequently feel sleepy during the day. These patterns can exist irrespective of the presence of any sleep disorder, including delayed sleep phase disorder.

A focus on diagnosing sleep disorders may take our focus away from where it needs to be. There is great potential to improve teenagers’ sleep in primary care with thorough understanding of the expected changes in sleep seen in this age group, as well as awareness of the prominent issues. This would allow tailored, effective promotion of strategies teenagers can use to achieve good sleep health.

 

**The authors have identified many of the limitations of this study.  Notably, the questionnaire has been validated in adults against subjective assessments by an experienced sleep clinician.  It should be noted that for disorders that are normally objectively assessed, such as obstructive sleep apnoea, this questionnaire only provides an indication of potential risk.

Food cravings and sleep Karyn O'Keeffe Sep 10

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Some of you may have seen or heard last month’s news reports stating that when we are sleep deprived, we crave junk food.  These reports stemmed from a study conducted by Stephanie Greer and her colleagues at the University of California, Berkeley, which investigated changes in brain function after one night’s sleep deprivation, compared to a preceding night of healthy sleep.  The researchers found that not only are the areas of our brain that make complex decisions impaired when we are sleep deprived, but there is more brain activity in the areas that control desire.  When participants were shown a series of food images and asked to rate their desire for each item, they preferred high calorie foods, like burgers and pizzas.

Greer’s study adds to a growing body of work in this area and an increasing understanding of how short sleep might contribute to weight gain and obesity.  We know that those of us who don’t get enough sleep have abnormal glucose metabolism, and abnormal hormonal control of appetite and satiety (feeling full).  We tend to overeat when we are missing out on sleep.  We crave high-calorie foods, we snack more often, our meal times become more irregular, and a higher proportion of our diet comes from fats and refined carbohydrates.

This week the link between junk food and sleep deprivation is back in the news.  Colin Chapman at Uppsala University in Sweden studied the effect of sleep deprivation on our food purchasing choices.  Participants were given a fixed budget and a representative selection of supermarket items, and asked to spend their entire budget on whatever foods they wanted.  Following a night of sleep deprivation, they purchased more calories and greater portion sizes than when we they were well-rested.

Makes me wonder whether those days when my grocery bill is obscenely high, and I seem to have far too many packets of biscuits in the trolley, follow nights of bad sleep.

Later school start times for NZ teenagers Karyn O'Keeffe Jul 05

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Last week, Radio NZ interviewed Dr Paul Kelley, an educational researcher from the UK, on educational outcomes in adolescents when school timing is shifted to a later start time.  From a sleep science point of view, I wasn’t blown away by Paul’s interview and I was surprised that Radio NZ had opted to not to describe any of the New Zealand research that had been done.  So I thought I would…

Both local and international research has shown that teenagers get less than the optimal amount of sleep.  This has a number of implications.  Sleep loss in teenagers is associated with weight gain, substance use, motor vehicle accidents, low self-esteem and poor academic outcomes.

Noticeable changes are seen in sleep and circadian (body clock) biology during adolescence.  Not only does the structure of our sleep change, but the timing of our circadian clock shifts later relative to the day/night cycle.  That is, teenagers have a biological shift to later bed times and wake times relative to the start of the waking day, which is more pronounced in older teenagers.

We see a distinct difference in total sleep time between school and non-school days that is partly due to this biological change in the circadian clock.  Teenagers who try to go to bed at a time that allows them get enough sleep before school may find it difficult to get to sleep.  On school days, when they are required to wake early, their sleep may be cut short.

However, the shift to later bed and wake times is a little more complex than a pure biological shift in the circadian clock.  There are a number of psychosocial and behavioural factors which contribute to this sleep pattern.  For example, there is often increasing autonomy in use of technology, ‘screen’ time and social interaction during adolescence.  The stimulating nature of these activities may mean that bed time is pushed later.  In addition, exposure to bright light (screens), and in particular blue-enriched light, during the evening can have an effect on the timing of our circadian clock.

During the recent Radio NZ interview, Paul Kelley described changes he had helped initiate in UK schools to shift school start times later, in order to improve opportunity for sleep.  Here in New Zealand, Wellington High School independently decided to make similar changes in 2006.  Years 12 and 13 students at Wellington High School start school at 10.30am.

This change in school start times at Wellington High School was prompted by the findings of a pilot study conducted by Brigid Borlase at the Sleep/Wake Research Centre, who had examined sleep issues in Wellington High School students in 1999.  Brigid also conducted a follow-up study in 2008 to assess the impact of the change in school start time by comparing Year 12 students from 2008, with Year 12 students from 1999 and Year 11 students from 2008 (with a 9am start time).

In 2008;

  • late start students got more sleep, were less sleepy and were less likely to say they missed out on sleep than early start students from 1999 or 2008
  • late start students were more likely to report that it was easy for them to get up in the morning and that they felt ok on waking
  • early start students were more likely to report missing out on sleep on school nights than late start students
  • students who had more technology the bedroom slept less

There are limitations to this study.  The study relied on self-reports from the students.  It is not known how these findings relate to academic outcomes, but anecdotal reports from the teachers at Wellington High School suggest that students are more alert, responsive and engaged in the classroom.  There have also been significant changes in technology between 1999 and 2008, which was reflected in a substantial increase in the number of students with technology in the bedroom (81% in 1999; 96% in 2008).  This study did not capture the amount of time spent using these devices, or when they were used.  The study findings hinted that these students were using the extra time available for sleep.  They didn’t appear to be shifting their bedtimes any later, but were waking later in the morning.  It would be great to capture the specific changes adolescents make in their sleep behaviour alongside interventions like this.

Alcohol: sleep aid or hindrance? Karyn O'Keeffe Jun 11

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Many of us are aware that we get off to sleep quite easily when we drink large amounts of alcohol before bed, and its sedating effects sometimes mean that alcohol is used as a sleep aid in those that are having trouble sleeping.  However, alcohol is very disruptive to sleep (some of us may have experienced this on nights where we’ve partied a little too hard).

Although the effects of alcohol on sleep have been studied for well over a hundred years, most of the research on specific aspects of sleep has been conducted since the 1930s.  These early studies suggested that alcohol had a two pronged effect, with sleep structure and movement changing from the first to the second half of the night.  These effects vary by the amount you drink.

The majority of laboratory studies investigating the effects on alcohol on sleep have given a single dose of alcohol shortly before bed, with the aim of peak blood alcohol concentrations at bedtime.  If you go to bed with alcohol your system, you will likely take less time to get off to sleep, and you won’t wake as often during the first half of the night.  You will, however, wake often during the second half of the night.

Your sleep structure will also change.  The severity of these changes increases considerably with dose but overall, you will most likely have an increase in slow wave (deep) sleep in the first half of the night.  However, this increase is at the expense of REM sleep.  Your REM sleep, therefore, occurs much later in the night than usual, and the overall amount of REM sleep is decreased.  The REM sleep that you do get is concentrated in the second half of the night.  During REM sleep, our sympathetic nervous system activity is a lot more variable, and we have frequent changes in heart rate, breathing, and gut activity.  We also don’t thermoregulate well.  A nice combo which adds to that broken sleep.

Smartphone sleep apps Karyn O'Keeffe May 06

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For a few months now, I’ve been playing around with a sleep app to get a better idea of how easy they are to use, what data I could collect, and whether I’d remember to input my sleep data every day.  When I first started using it, I was mainly interested in my sleep duration and sleep timing.  Recently though, I’ve noticed the developers for my particular app have been adding more and more bells and whistles.  There was always the option to indicate lights on and off times for your sleep period, with additional options to limit phone functions, such as receiving calls and emails overnight.  However, my app now claims that it can use the accelerometer in my smartphone to accurately detect movement overnight, and interpret movement as sleep stages.

Many apps now include this feature, and provide users with a range of outputs from basic sleep structure to specific recommendations about how to improve sleep alongside their behaviour and sleep patterns.  What is concerning though, is that some of these recommendations are not scientifically-based or in line with best practise.  Most of these apps also claim to be extraordinarily accurate in their movement detection and sleep stage interpretation.  These claims are somewhat surprising given that sleep researchers themselves have been using movement as a surrogate for sleep and wake for some time, and not one of us thinks we can accurately interpret sleep stages from that data.  (Believe me, if it was possible, we would use it in a second.)

Activity monitors (actigraphs) are fairly reliable at detecting total sleep time (sleep duration).  Although not quite as accurate, they also provide an acceptable measure of sleep onset latency (the time from lights out to falling asleep) and sleep fragmentation (broken sleep).  Actigraphs are less reliable in clinical populations than in healthy adults.  It is not known whether this reduced accuracy extends to those with sub-clinical sleep difficulties.

Actigraphs cannot reliably measure different sleep stages, and I think this is highly evident in the graphical representations of sleep that many of these apps produce.  Often their sample diagrams show vastly abnormal sleep structure, and slow wave sleep shortly before waking.  If you’re getting a healthy amount of sleep each night, slow wave sleep just prior to waking is extremely unlikely.

Many sleep apps now include a feature to optimise our time of waking, so that we wake from light sleep. This is purported to reduce sleep inertia, which is a sensation of grogginess, confusion and decreased functioning, experienced immediately on waking.  Waking from slow wave sleep is thought to contribute to sleep inertia; however, sleep structure, sleep routine and time of day are also likely to be involved.  However, if we are to assume that sleep stage detection was reliable and given that regularly waking from slow wave sleep would suggest restricted sleep duration, and/or poor sleep routine or timing, I wonder if the focus should be on improving overall sleep health, rather than fixation on alarm clock times.

That said, a few apps provide great advice on healthy sleep, with sensible advice on how to achieve it.  Additionally, many people report benefit from using these apps (for example, waking feeling more refreshed) but I’m inclined to think that this results from a focus on achieving better sleep, and perhaps the effect of receiving personalised feedback on your own sleep, than the performance of the app itself.

Daylight savings: There’s no spring to my step Karyn O'Keeffe Sep 28

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Most of us don’t look forward to the switch to daylight savings time that will be required on Saturday night. I know I’m not. It’s not just the hour of sleep lost; daylight savings also requires a resetting of our circadian body clock. And this is where things get complicated, because the interaction of the two has follow-on effects in the days following daylight savings.

Daylight savings time is all about shifting our daylight hours so they align optimally with our working day. The upcoming transition to daylight savings time provides a way of shifting our daylight hours to be one hour later. This transition means that we shift our day/night cycle one hour forward in relation to our internal circadian body clock and therefore, to adjust to the new day/night cycle, we need to shunt our circadian clock one hour back. On Saturday night, we are going to lose an hour out of circadian clock’s day. It’s not going to like it.

Studies have shown that on average, we will get about an hour’s less sleep on Saturday night (that is, we don’t tend to strategically make up for missed sleep on that night). Missing out on sleep will help us get to bed an hour earlier on Sunday night and in fact, our bed times seem to adjust quite quickly after the switch to daylight savings time. Consistent sleep loss certainly helps push bed times earlier.

Unfortunately, our circadian body clocks don’t make such a quick adjustment. Because our circadian clocks influence our sleep/wake timing, our sleep structure changes and we often wake earlier than we’d like in the days following the switch to daylight savings time. You may recall me saying in a previous post that our circadian clock prefers to drift later. This means that it is much easier for us shift to our sleep times later, than earlier. There is some variability between individuals but in general, it takes about a week for our wake times to adjust to the new schedule. There is also some evidence to suggest that the shorter the sleep we usually get, the harder it is for us to adjust.

While it is clear that there are direct effects on sleep and circadian rhythms resulting from the transition to daylight savings time, there is conflicting evidence about the follow-on effects on waking function. Additionally, studies are not always comparable, with varying classification of degrees and type of accident or injury; and different study populations. That said, the transition to daylight savings time may be associated with increased motor vehicle and workplace accidents, as well as decreased productivity.

So what can you do to minimise the impact of the transition to daylight savings time on your sleep and waking function?

  1. Try to optimise the amount and quality of your sleep in the days leading into daylight savings. Missing out on sleep means you will cope less well. Follow good sleep habits – get a healthy amount of sleep (7-9 hours) at a healthy time of the day; avoid caffeine, nicotine and excessive alcohol; and optimise your bedroom environment.
  2. Try to shift your bed and rise times 15-30 minutes earlier in the days prior to daylight savings.
  3. Expose yourself to sunlight in the mornings leading into daylight savings. Open the curtains in the room you are in. Even better, go for a 20-30 minute walk first thing in the morning (but ensure you don’t cut into your sleep time to do this).

Should I cram all night before that exam? Karyn O'Keeffe Sep 25

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I’m going to give a presentation to some law students in a couple of weeks. Along with providing information about normal sleep and what can affect it, I’d like to convey that short sleep is not a good strategy for optimising learning.

Short sleep amongst students is not uncommon. As a teenager, our circadian body clock naturally drifts later. Those late bedtimes and lengthy sleep-ins we see in teenagers are actually a normal physiological phenomenon. Our body clock generally returns to ‘normal’ in our early twenties. However, late bedtimes in teenagers and young adults, coupled with required early rise times due to school and other commitments, often means their sleep is cut short.

Alongside this, our behaviour can sometimes boost these changes in the timing of our circadian body clock. Most university students, at some time or other, have probably worked long hours after uni to pay the rent, worked all night on an assignment you really should have started two weeks ago because it’s due tomorrow, or simply gone out quite late and stayed out really late. Regular late night activity helps reinforce our body clock to later bedtimes and later rise times. More often than not, they lead to short sleep.

So how does short sleep relate to learning? Well, there are a number of studies in this area but a recent study in high school students showed that increased study time outside school was associated with decreased school performance (that is, understanding information in class or doing poorly on a test). However, after further analysis, it became evident that increased study time was associated with poor performance because it cut into sleep time.

This is not to say, of course, that increased study time is not beneficial for learning (there clearly is a relationship), but it does highlight that extending one’s daily activities at the expense of sleep, will likely lead to decreased academic performance the following day.

Learning new information while we sleep Karyn O'Keeffe Aug 31

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This week brings some exciting findings about sleep and learning.  In particular, in a study to be published in the journal Nature Neuroscience, Arzi and colleagues have shown that it’s possible to learn new information during sleep.

To date, research has largely focussed on information storage during sleep rather than new information processing during sleep.  For example, we know that the learning of varying types of information is enhanced with sleep, and that different types of information are better learnt during different sleep stages.

However, up until now we haven’t seen many studies that have successfully demonstrated that we might be able to learn new information while we are asleep.  Using very simple forms of associative learning, researchers have previously demonstrated that animals, such as rats, and human infants are able to process some types of information during sleep.  In these studies, the brain centres activated during sleep were the same as those we use when we unconsciously process information (eg, motor skills when learning to ride a bike). 

To date, no studies have successfully shown that we can actively process during sleep information we have learnt consciously (eg, remembering the trip you took at Christmas 2003, knowing that your bright red sweater needs to be washed separately).  However, in a group of young adults, Arzi has shown that we might be able to process this type of information during sleep.

Different tones were played to sleeping adults and each time a particular smell was wafted past their nose.  Particular tones were linked to particular smells – pleasant (deodorant, shampoo) or unpleasant (rotten fish or flesh) – and the sniff response to each measured.  (A strong sniff response is linked to a pleasant smell and a weak response to an unpleasant one.)  The tones were repeated many times during the night and the  researchers were then able to test whether an association had been learnt between the tones and a particular smell.

Arzi and colleagues showed two fairly exciting things.  We seem to be able to learn during our sleep and demonstrate that learning during the same sleep period.  When tones only (no odour) were played in the second half of the night, the matching sniff response was demonstrated.  Information learnt during sleep continues into wakefulness.  When the tones only were played during the following day, the matching sniff response was demonstrated.

This is very much a first step in this area and it will be interesting to see where this study leads.  It is definitely unclear whether more complex learning is possible during sleep, and then if it is, what function or role this type of learning could serve.

Driving drowsy is like driving drunk Karyn O'Keeffe Aug 10

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This one is an oldie but a goodie, and still as relevant as ever…

Just over 10 years ago, Australian researchers showed that our performance at the end of the day, on a day where we’ve decided to stay up late, was similar to our performance when driving drunk. 

Essentially they compared how we function when given a placebo drink, at different levels of alcohol intoxication, and when we are asked to stay awake for long periods of time.  Not surprisingly, our performance on a range of simple and complex tasks gets worse as our blood alcohol levels (BAC) increase.  However, our performance also gets worse the longer we stay awake.  These individuals woke up at the beginning of their normal day, stayed awake all day and then were asked to stay up through the following night.  All up, they were awake for 28 hours.

It seems our performance stays fairly stable up to 17 hours after we wake (on a usual working day, about 11pm) but after then it steadily declines.  Our ability to do complex tasks, such as driving, decreases much more rapidly than our ability to do something simple like respond to a single visual cue.

They found that our performance after we have been awake for sometime in the range of 17-19 hours is similar to that when we have a BAC of 0.05% (the legal driving limit in many countries).  They also found that our ability to function after we have been awake for about 20 hours (about 2am) (on complex tasks like driving) and about 25 hours (on the simplest tasks), was similar to our performance at a BAC of 0.10% (over the limit in New Zealand).

Something to think about…

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