A recent study in the Journal of the American Heart Association has led to headlines that will make you rethink your Saturday morning sleep in.
Don’t set the alarm just yet. Yes, the researchers found a link between people who usually slept for longer than eight hours a night and their chances of having heart disease or dying prematurely.
But they didn’t show that sleeping longer caused these health problems. It might be that people with health, psychological or social problems are more likely to sleep for longer.
How was the research conducted?
The research article investigated links between sleep duration and cardiovascular disease and death. Cardiovascular diseases affect the heart and blood vessels, and include heart attacks and strokes. They’re a leading cause of death but many of the risk factors are modifiable health behaviours, such as not getting enough exercise.
The authors investigated the cardiovascular risk associated with each hour below seven hours – and each hour above eight hours – of sleep per night. They also looked at the link between sleep quality, cardiovascular disease and death.
The authors pooled together 74 existing studies from 1970 to 2017, covering 3.3 million participants.
In this case, the existing studies used population registries, death certificates, questionnaires, interviews and medical records to gain information about cardiovascular disease and health. To gain information on sleep duration, they used questionnaires or interviews.
What did they find?
The researchers found getting more than eight hours of sleep was associated with an increased risk of cardiovascular disease – a 17% increase for nine hours and a 23% increase for ten hours of sleep.
They also found a link between longer sleep times and an increased risk of premature death – a 23% increase for nine hours, a 52% increase for ten hours and a 66% increase for 11 hours of sleep.
Sleep durations of less than seven hours were also associated with strokes, although to a lesser extent than longer sleep durations. Five hours of sleep was associated with a 29% increased risk of strokes, compared to a 41% increase with ten hours of sleep.
Poor sleep quality wasn’t associated with increases in premature death, but it was associated with a 44% increased risk of coronary heart disease.
The authors conclude that sleeping longer than seven to eight hours a night may be associated with a moderate degree of harm compared to sleeping for shorter than recommended. Sleep duration and quality, they say, may therefore be helpful markers for increased cardiovascular risk.
Based on this, they suggest clinicians:
be aware people who report sleeping too much or waking up feeling unrefreshed warrant further clinical assessment
promote good sleep practices and discuss sleep with patients.
What does it all mean?
Don’t make any rash changes to your sleeping patterns just yet. We can’t conclude from this study that longer sleep causes cardiovascular disease or a greater risk of early death. There appears to be a correlation, but given the design of the study, we can’t establish causation.
Before we even go as far as saying there’s a correlation between longer sleep duration and cardiovascular disease, there are a few things to take into account.
The included studies used subjective measures of sleep, and the length of time in which the participants were asked about their sleep duration (in the past week, month or year) may have varied.
Lab-based sleep studies show it’s really hard to remember how long it took you to fall asleep, how many times you woke up during the night, and how much sleep you got in total. Quite often the amount of time a person spends in bed as opposed to the amount of time a person is asleep in bed can affect these subjective ratings of sleep duration and quality.
So, at best, we can say people who feel like they sleep more and have poorer sleep quality may be at higher risk of developing cardiovascular disease.
Because this is a meta-analysis (which pooled 74 studies), the authors also acknowledge we can’t look at individual patient-level data. Therefore, assumptions can’t be made about the links between cardiovascular disease, sleep and other risk factors that might have been at play.
In other words, a whole range of other underlying issues probably contributed to these findings. Health issues that can lead to increased subjective sleep duration or reduced sleep quality include depression, obstructive sleep apnoea, anaemia, inflammatory disorders and other sleep disorders.
There are also many psychological and social factors that might influence how much a person sleeps. Unemployment, low socioeconomic status, low levels of physical activity and poor nutrition can all lead to increases in sleep duration and feelings of being unrefreshed during the day.
A lot of these health issues and psychological factors happen to be well-known risk factors for cardiovascular disease. So, it’s probable these factors are the underlying mechanisms leading to an increased risk of cardiovascular disease and increased sleep duration, rather than too much sleep directly affecting cardiovascular risk.
The question of how sleeping too much affects health is interesting and important to investigate further using different research designs. Cohort studies, where large groups of people are studied over a long period, would allow us to investigate and draw more solid conclusions about the causal links between sleep duration and health.
Is it better to sleep less?
If you’re tempted to stay up late to squeeze in a few more episodes of your favourite TV show, think again. Many studies conducted in controlled, experimental conditions show not getting enough sleep affects physical and psychological functioning and can contribute to the development of chronic health issues such as type 2 diabetes.
Most adults need around seven to nine hours of sleep a night, but individual sleep needs can vary greatly. Make sure you get enough sleep so you feel refreshed and be sure to share any concerns about your sleep with your doctor. – Stephanie Centofanti and Siobhan Banks
Blind peer review
This is a fair and accurate assessment of the study and its findings. Self-reports of sleep are not always reflective of true sleep duration or quality. And it’s likely other health conditions are the underlying reason for the increased risk.
People should listen to their own body when determining how much sleep is the right amount for them, as sleep duration can vary greatly between individuals. – Gemma Paech
Research Checks interrogate newly published studies and how they’re reported in the media. The analysis is undertaken by one or more academics not involved with the study, and reviewed by another, to make sure it’s accurate.
You may be familiar with that feeling of overwhelming sleepiness during the mid-afternoon. It’s common, occurs whether you’ve eaten lunch or not, and is caused by a natural dip in alertness from about 1 to 3pm. So, if you find yourself fighting off sleep in the middle of the day and you’re somewhere where you can have a nap, then do it.
Taking the time for a brief nap will relieve the sleepiness almost immediately and improve alertness for several hours after waking. And there are many other benefits too.
Understanding why we nap
People nap for lots of reasons, some which are:
to catch up on lost sleep
in anticipation of sleep loss to avoid feeling sleepy later on
for enjoyment, boredom or to pass time.
Napping is relatively common. In fact, about 50% of us report taking a nap at least once per week.
Napping rates are greater in countries like Greece, Brazil and Mexico that have a culture of siesta, which incorporate “quiet time” in the early afternoon for people to go home for a nap. In such countries, up to 72% of people will nap as often as four times per week.
Naps are not only beneficial because they make us feel less sleepy and more alert, but because they improve our cognitive functioning, reaction times, short-term memory and even our mood.
Our research (not yet published) has found those who regularly nap report feeling more alert after a brief nap in the afternoon when compared to those who only nap occasionally.
Another research group found that motor learning, which is where brain pathways change in response to learning a new skill, was significantly greater following a brief afternoon nap for regular nappers when compared to non-nappers.
In fact, the overall benefits of naps are similar to those experienced after consuming caffeine (or other stimulant medications) but without the side effects of caffeine dependence and possibly disrupted sleep at night time.
The amount of time you spend napping really depends on the time you have available, how you want the nap to work for you, and your plans for the coming night. Generally speaking, the longer a nap is, the longer you will feel rejuvenated after waking.
Long naps of one to two hours during the afternoon will mean you are less sleepy (and require less sleep) that night. This could mean it will take longer than usual to fall asleep.
If you are planning to stay up later than usual, or if taking a little longer to fall asleep at bedtime is not bothersome, time your nap for about 1.5 hours. This is the length of a normal sleep cycle. You will experience deep sleep for about an hour or so followed by light sleep for the last half an hour.
Waking up during light sleep will leave you feeling refreshed and alert. However, waking during deep sleep will not. If you sleep too long and miss the light sleep at the end of a nap, chances are you will wake up feeling sluggish and drowsy. If you do experience feeling drowsy after a nap, don’t worry – this feeling is temporary and will go away after a while.
Another option is to have a brief “power” nap. Brief naps of 10-15 minutes can significantly improve alertness, cognitive performance and mood almost immediately after waking. The benefits typically last for a few hours.
Power naps are great because you won’t experience any sluggish or drowsy feelings after waking. This is because you do not enter any deep sleep during this brief time.
Research suggests, a brief, early-to-mid-afternoon nap provides the greatest rejuvenation when compared to naps at any other time of the day. However, if you’re struggling to stay awake, a brief nap taken at any time can be help keep you alert.
If you need an alarm to get up in the morning, you’re probably not getting enough sleep.
More than 40% of Australians get too little sleep to feel rested and able to function at their best. The average amount for an adult is around seven hours, while only 8% are lucky enough to get more than nine hours. Some 12% of Australians get less than 5.5 hours, and three-quarters of those struggle to get through their day.
These holidays, ditch the alarm clock and make getting enough sleep one of your New Year’s resolutions. Your memory, waistline and even your employer may thank you for it.
Why getting enough sleep should be a priority
Our brains use sleep time to sort through our experiences. We “clean up” and get rid of information connections we don’t need from the day just gone. Without adequate sleep, we may not be making enough space for new learning and memories.
Getting enough sleep also ensures we are safe to drive on the roads and less likely to make costly mistakes at work and home. Being awake for longer than 17 hours impairs your ability to think clearly as much as having a blood alcohol concentration above 0.05. After 24 hours awake, your ability to perform cognitive tasks is as poor as if you had a blood alcohol concentration of 0.10.
Last year’s Australian sleep survey found 29% of Australian workers reported making errors at work in the previous three months specifically because they hadn’t got enough sleep. One in five respondents reported having nodded off while driving.
Your ideal sleep duration will be unique to you and fall somewhere within the recommended range. To find out how much sleep you need, try a week-long experiment and modified sleep regime. Think of it as your holiday homework:
Cut back on how much you are doing during the week, particularly in the evening, to give yourself time to wind down
Put away the technology. A tech ban in the bedroom might be the best start
Create a dark sleeping space
Get rid of the alarm clock so your body has the chance to tell you how much sleep you need
Keep a week-long diary of your sleep times and daytime energy levels to get a feel for how much sleep feels good the next day.
You might find you need to sleep longer than usual for the first couple of nights. But remember, this is an exercise to work out how sleep can help you feel good rather than a test to see how much sleep you “must” or “can” get as this pressure may not help with sleeping well.
You might feel a little groggy the next morning which is normal, but you should wake up – and get up – when you feel well-rested.
By seeing where you sit on the sleep spectrum, you can work out the bed and wake times that best suit your needs.
How to get more sleep
Here are some starting points to make sleep more of a priority.
1) Reduce your exposure to bright lights in the evening
Allowing your body to naturally respond to the light and dark cycle each day can lead to earlier bed times.
Ditching distractors that delay our bedtimes can help shift the increase in the hormone melatonin, which makes us sleepy, to earlier in the evening.
As little as one weekend of camping away from electrical lighting, including blue light in our devices, can help us become early risers.
If there’s no time for camping this Christmas, try a “camp at home” approach by reducing your light exposure throughout the house at night; dim and fewer lights in the evening is ideal.
2) Establish a routine
While some find falling asleep a breeze, this can be a slow process for many. Consistent activities – such as brushing your teeth, reading a book – at a regular time each evening can help your body recognise and prepare for heading to bed.
Make sure this time is in addition to the time you set aside for sleep, so you have enough time to wind down before bed.
This routine extends to consistent wake times. A regular bed and wake time schedule should be complimentary.
3) Talk to your doctor about your sleep
If you’re told you snore, or you never feel refreshed even after what seems to be a long sleep, talk to your GP about whether you might have an underlying disorder that makes getting enough sleep harder.
While time spent sleeping may feel akin to “doing nothing” for your health, the benefits of regular, refreshing sleep for your brain and body mean that it should be on your New Year’s resolution list right next to healthy eating and exercise.
Many of us have experienced the effects of sleep deprivation: feeling tired and cranky, or finding it hard to concentrate. Sleep is more important for our brains than you may realise.
Although it may appear you’re “switching off” when you fall asleep, the brain is far from inactive. What we know from studying patterns of brain electrical activity is that while you sleep, your brain cycles through two main types of patterns: rapid eye movement (REM) sleep and slow-wave sleep.
Slow-wave sleep, which occurs more at the beginning of the night, is characterised by slow rhythms of electrical activity across large numbers of brain cells (occurring one to four times per second). As the night progresses, we have more and more REM sleep. During REM sleep we often have vivid dreams, and our brains show similar patterns of activity to when we are awake.
Sleep serves many different functions. One of these is to help us remember experiences we had during the day. REM sleep is thought to be important for emotional memories (for example, memories involving fear) or procedural memory (such as how to ride a bike). On the other hand, slow-wave sleep is thought to reflect the storing of so-called “declarative” memories that are the conscious record of your experiences and what you know (for example, what you had for breakfast).
But is it that important for you to remember what you had for breakfast? Probably not – that’s why the brain needs to be selective about what it remembers. Sleep allows the brain to sift through memories, forgetting certain things so as to remember what’s important. One way it may do this is by “pruning away” or “scaling down” unwanted connections in the brain.
This is thought to counterbalance the overall strengthening of connections that occurs during learning when we are awake. By pruning away excess connections, sleep effectively “cleans the slate” so we can learn again the next day. Interfering with this scaling down process can, in some cases, lead to more intense (and perhaps unwanted) memories.
The importance of sleep for keeping our brains optimally active may be reflected in our changing sleep patterns as we age. Babies and children sleep much more than adults, probably because their developing brains are learning much more, and being exposed to new situations.
Sleep is also needed to do a bit of brain “housekeeping”. A recent study in mice found sleep cleanses the brain of toxins that accumulate during waking hours, some of which are linked to neurodegenerative diseases. During sleep, the space between brain cells increases, allowing toxic proteins to be flushed out. It’s possible that by removing these toxins from the brain, sleep may stave off neurodegenerative diseases like Alzheimer’s.
When you haven’t had enough sleep, your brain may force itself to shut down for a few seconds when you’re awake. During this “micro-sleep” you may become unconscious for a few seconds without knowing it. Drowsiness while driving is a leading cause of motor vehicle accidents, with sleep deprivation affecting the brain just as much as alcohol. Sleep deprivation can also lead to fatal accidents in the workplace – a major issue in shift workers.
The beneficial effects of sleep on attention and concentration are particularly important for children, who often become hyperactive and disruptive in class when they don’t have enough sleep. One study found getting just one hour less sleep per night over several nights can adversely affect a child’s behaviour in class.
What are the long-term effects?
The longer-term effects of sleep deprivation are more difficult to study in humans for ethical reasons, but chronic sleep disturbances have been linked to brain disorders such as schizophrenia, autism and Alzheimer’s. We don’t know if sleep disturbances are a cause or symptom of these disorders.
Overall, the evidence suggests having healthy sleep patterns is key to having a healthy and well-functioning brain.
Putting up a post on this Blog is hopefully an indication that I’m beginning to get back on track. This has been a particularly difficult period for me and I’m sure I’m not out of the woods just yet. I do feel I have turned a corner though and that is a very good think – I think.
To help me get back on track I’m actually taking a week off work from Christmas Eve until New Year’s Day, returning the following day. I’m really looking forward to a week of sleep, rest and relaxation.
It has been such a long time since I sat down and read a book – even a chapter. I have found that when I get down/depressed I just don’t want to read – even though it would probably lift my spirits. It just seems too hard to do. This is something I hope to correct starting tomorrow – I probably should start this right now as tomorrow I will probably decide against it. The only reason I won’t start today is I am simply too tired and I need to get to bed soon. This post will remind me to do so
tomorrow – I hope.
Well before this time on a Sunday I have already began to think, ‘is it the end of the weekend already?’ Yeah, I could do with a longer break. I have slept well both Friday and Saturday nights, with a great amount of sleep – yet I feel so tired just thinking about going back to work. I am way too tired at the moment.
I enjoy my job – I’m just so tired at the moment. There is a long weekend coming up soon – three days off. I’m so looking forward to that. Sadly, I think I have to work on the Saturday though. I could really use the break.