Tag Archives: sleeping

Going to sleep before 10 PM could lower your risk of heart disease

Going to bed between 10 and 11 PM may be good for your heart — especially if you’re a woman.

It’s been shown time and time again that not getting enough sleep is bad for your heart (and bad for you in general, for a number of reasons). But not all sleep is equal, and not all bedtimes are equal. In a new study, researchers analyzed data from over 88,000 individuals in the UK Biobank, collecting data on their sleep and waking up time using a monitoring bracelet. Researchers then followed up four years later, looking for any cardiovascular diseases (such as heart attack, heart failure, chronic ischaemic heart disease, stroke, and transient ischaemic attack). Over 3,000 people developed cardiovascular disease over the period of the study.

The ideal period for going to sleep (the one that was correlated with the lowest risk of heart disease) was 10-11 PM. Many of the people who developed a disease went to sleep after 11 PM — the risk was 12% greater for those who went to sleep between 11:00 and 11:59 PM, 25% disease higher for those going to bed after midnight, and remarkably, 24% higher for those who went to sleep before 10 PM.

While this is just relative risk, and the total risk was still relatively low (just 3.6% of participants developed a disease), the differences are significant, especially because the data was acquired directly (as opposed to self-reporting, which is often used in this type of study but can be inaccurate).

Still, the study only establishes a correlation, which does not necessarily imply causation — so in other words, no cause-effect link was yet demonstrated. However, researchers stress that the link persisted after adjustments were made for sleep duration and sleep irregularity.

“The body has a 24-hour internal clock, called circadian rhythm, that helps regulate physical and mental functioning,” said study author Dr. David Plans of the University of Exeter, UK. “While we cannot conclude causation from our study, the results suggest that early or late bedtimes may be more likely to disrupt the body clock, with adverse consequences for cardiovascular health.”

However, there were important gender differences. The association with increased cardiovascular risk was stronger in women — only sleeping before 10:00 PM remained as significant for men. Researchers aren’t exactly sure why this seems to be the case, but they suggest that sleep timing may be a risk for everyone, not just for women.

“While the findings do not show causality, sleep timing has emerged as a potential cardiac risk factor – independent of other risk factors and sleep characteristics. If our findings are confirmed in other studies, sleep timing and basic sleep hygiene could be a low-cost public health target for lowering risk of heart disease.”

Based on these findings, researchers suggest to try and go to sleep sometime between 10 and 11 PM — or at least before midnight. The more you delay, the more pressure you are likely putting on your body.

“Our study indicates that the optimum time to go to sleep is at a specific point in the body’s 24-hour cycle and deviations may be detrimental to health. The riskiest time was after midnight, potentially because it may reduce the likelihood of seeing morning light, which resets the body clock,” Plans added.

Going to bed before midnight can be pretty challenging, especially in our modern, fast-paced world. However, here are a few science-based things you can do to ease your way into a good night’s sleep:

  • Turn off all artificial lights — yes, this includes your smartphone, laptop, TV, whatever. Because the natural production of melatonin (which is required for sleep) can be suppresed by light, looking into a screen may prevent the body from feeling sleepy.
  • Staying away from caffeine hours before bedtime — give enough time for the caffeine to exit the body.
  • Stay physically active — there is solid evidence that physical activity can help improve your sleep quality. Intense physical activity less than two hours before bedtime should be avoided, but otherwise, exercising really helps.
  • Meditation and relaxation techniques can also help — although more research is needed, there is evidence that things like breathing exercises, meditation, and relaxation methods can help reduce your stress levels and help you fall asleep faster.

Journal Reference: Nikbakhtian S, Reed AB, Obika BD, et al. Accelerometer-derived sleep onset timing and cardiovascular disease incidence: a UK Biobank cohort study. Eur Heart J Digit Health. 2021. doi:10.1093/ehjdh/ztab088.

Genetic mutation explains why some people need to sleep fewer hours

Sleeping the full eight hours usually advised by doctors might not be necessary for everybody, according to a new study, which suggested there’s a gene that dictates how much sleep a person needs.

A researching team at the University of California, headed by Ying-Hui Fu, analyzed the genes of 12 members of a family that sleeps as little as 4.5 hours per night without feeling tired. They found they had a mutation in a gene called ADRB1.

“We all spend about one-third of our lives in the state of sleep,” Fu said. “In fact, considering how important sleep is to our well-being, it’s astonishing that we know so little about how sleep is regulated.”

The team bred rats with the same mutation, which slept about 55 minutes less per day. This correlated with altered activity in a brain region called the dorsal pons that is known to regulate sleep.

In normal rats, ADRB1-expressing brain cells were found to be inactive during most sleep stages, but active when they were awake. In the mutant ones, these cells were even more active during waking hours. The researchers also found they could wake up sleeping rats by artificially activating these ADRB1-expressing brain cells.

The results suggest that ADRB1-expressing brain cells promote wakefulness and that variations in the ADRB1 gene influence how long we can stay awake for each day, said Fu. Her team has previously found that mutations in other genes like DEC2 also make people need to sleep less.

These mutations don’t seem to be associated with any negative health consequences. “Most natural short sleepers are very happy about their sleep pattern – they usually fully take advantage of their extra time,” Fu told New Scientist.

The researchers think the ADRB1 and DEC2 mutations must have emerged recently in human history and haven’t had time to spread widely yet. “The 8-hour norm has been the standard for a long time, but somehow a few new mutations occurred recently and produced this seemingly advantageous trait,” Fud said.

While this is newly discovered mutated gene contributes to short sleep, the study highlighted it’s probably not the only one. There are likely more unrecognized genes and regions of the brain that tell our bodies when to go to bed and rise in the morning.

“Identifying genes, and mutations, that cause people to sleep less naturally without significant negative impact lays the groundwork for scientists to investigate how our sleep homeostasis and efficiency is regulated at the molecular and neuronal levels,” Fu says.

Lack of sleep makes your brain start eating itself

Lack of sleep in mice sends their brains into overdrive — making them “cleaner” in the short run, but causing brain damage in the long run.

Image via Max Pixel.

Burning the midnight oil might burn your brain itself. We all like to “steal” as much as possible from the day, but sleep is a price we simply have to pay for our bodies functioning, and trying to cheat sleep only ends up cheating yourself. Michele Bellesi of the Marche Polytechnic University in Italy wanted to see what effects sleep deprivation has on our brains, so she tried to simulate it on mice.

Basically, Bellesi found that in the short run, chronic sleep deprivation can actually be beneficial, clearing potentially harmful debris and rebuilding worn circuitry might protect healthy brain connections. However, in the long run, the brain goes into overdrive and starts destroying worn-out cells and putting people at a risk of Alzheimer’s and other neurological disorders.

Sleeping the garbage away

Sleeping is a complex phenomenon, still poorly understood. We do know that sleeping is much more than just the body replenishing its energy levels. For instance, research has shown that during sleep, the brain sweeps away the toxic byproducts of neural activity from the day. It’s like taking out the garbage inside your brain. Well, that process also takes place, even more intensely, when you’re chronically sleep deprived — which is bizarre in the first place and we don’t really know why this happens. But after a while, the damage starts to set in, affecting both neurons (the brain cells) and synapses (the connections between the brain cells); once that happens, even recovering the sleep isn’t really clearing the damage.

This happens because like all cells inside our body, neurons are “cleaned up” by glial cells, namely the microglial cells. These are the first and main form of active immune defense in the central nervous system. Synapses are maintained by astrocytes, which among other functions, prune unnecessary synapses and corrects their shape. These processes happen mostly when we sleep. What this study found is that they happen even faster when we don’t sleep enough — the brain “cleans” too much of itself, and starts devouring itself. It’s an unexpected discovery.

“We show for the first time that portions of synapses are literally eaten by astrocytes because of sleep loss,” says Bellesi.

An astrocyte cell grown in tissue culture stained with antibodies to be more visible. Image credits: GerryShaw / Wikipedia.

The finding could explain why a lack of sleep seems to make people more vulnerable to developing Alzheimer’s or similar conditions says Agnès Nadjar of the University of Bordeaux in France. Researchers are now investigating whether there is some way of repairing the damage, but the takeaway is pretty clear (and you can tell this to kids if you’re having problems sending them to sleep): if you don’t sleep enough, your brain will start to eat itself.

To our knowledge, this is the first study to show how these processes occur during sleep deprivation. It’s not clear if they are replicated on humans.

“We find that astrocytic phagocytosis, mainly of presynaptic elements in large synapses, occurs after both acute and chronic sleep loss, but not after spontaneous wake, suggesting that it may promote the housekeeping and recycling of worn components of heavily used, strong synapses,” the researchers report. “By contrast, only chronic sleep loss activates microglia cells and promotes their phagocytic activity … suggesting that extended sleep disruption may prime microglia and perhaps predispose the brain to other forms of insult.”

Journal Reference: Michele Bellesi, Luisa de Vivo, Mattia Chini, Francesca Gilli, Giulio Tononi and Chiara Cirelli — Sleep Loss Promotes Astrocytic Phagocytosis and Microglial Activation in Mouse Cerebral Cortex. Journal of Neuroscience 24 May 2017, 37 (21) 5263-5273; DOI: https://doi.org/10.1523/JNEUROSCI.3981-16.2017

We sleep to forget things, new study finds

Sleep is as mysterious as it is vital for our wellbeing. Over the decades, researchers have proposed several mechanisms through which sleep rejuvenates us, but we still don’t fully understand the big picture. Now, two recently published studies come up with an interesting explanation: we sleep to forget some of the things we learn during the day.

Image credits: Dagon / Pixabay

We store memories in networks in our brains. Whenever we learn something new, we grow new connections between neurons, called synapses. In 2003, Giulio Tononi and Chiara Cirelli, biologists at the University of Wisconsin-Madison, proposed something very interesting: during the day, we learn so much and develop so many synapses that things sometimes get fuzzy. Since then, the two and their collaborators have made quite a few interesting additions to that study.

For starters, they showed that neurons can prune out some synapses, at least in the lab. But they suspected the same things happens every day, naturally, in our brains — probably during sleep. So they set up a painstaking experiment, in which Luisa de Vivo, an assistant scientist working in their lab, collected 6,920 synapses from mice, both awake and sleeping. Then, they determined the shape and size of all these synapses, learning that the synapses in sleeping mice were 18 percent smaller than in awake ones. That’s quite a big margin. “That there’s such a big change over all is surprising,” Dr. Tononi said. This was a big tell and helped direct their efforts.

After this, they designed a memory test for mice. They placed the animals in a room where they would get a mild electrical shock if they walked over one particular section of the floor. They injected some of the mice with a substance that had been proved to prevent the pruning of new synapses. The mice that experienced this were much more likely to forget about the section and after a good night’s sleep, they tended to walk over the section again, while mice that slept normally remembered better.

Then, Dr. Tononi and his colleagues found that the pruning didn’t strike every neuron. Some 20% were unchanged, likely well-established memories that shouldn’t be tampered with. In other words, we sleep to forget — but in a smart way. Another interesting consequence might concern sleeping pills. These pills might interfere with the brain’s pruning process and might prevent the brain from forming memories properly.

Markus H. Schmidt, of the Ohio Sleep Medicine Institute, said that the studies make a very good point and found one of the benefits of sleep, but he questions whether this is the reason why we sleep.

“The work is great,” he said of the new studies, “but the question is, is this a function of sleep or is it the function?”

Of course, in would be very difficult to replicate this study on humans.

Journal Reference: Luisa de Vivo et al — Ultrastructural evidence for synaptic scaling across the wake/sleep cycle. DOI: 10.1126/science.aah5982



How weekend camping resets your body clock, explained by science

Camping is an excellent antidote to the ills of modern life, a new study has found.

Image credits: Life of Pix / Pexels

Whether it’s staying up too late watching Netflix, always browsing your phone, or just sitting for too long during the day, modern life can put a big pressure on our mental health and especially on our sleeping. But fret not, science has you covered — all you need to do is take your sleeping bag and your tent and head for the mountains or the woods.

“Our modern environment has really changed the timing of our internal clocks, but also the timing of when we sleep relative to our clock,” said Kenneth Wright, director of the sleep and chronobiology lab at the University of Colorado in Boulder. “A weekend camping trip can reset the clock rapidly.”

An earlier study from Wright has already proven that our modern exposure to electrical lighting causes about a two-hour delay in our internal clocks, due to the fluctuations in the hormone melatonin. Basically, we go to sleep later and this causes a lot of problems. Back then, they showed that a week of camping in the summer sun shifts those clocks back and resets your body back to its healthy, natural rhythm. But the first study took place during the study — does the same thing happen during the winter?

In order to answer this, Wright asked nine active people to camp during the chilly Colorado winter, around the winter solstice, when days were at their shortest, while five stayed home as a control. No flashlights, no phones, and no source of external light was allowed for the campers. Results were even better than those for the summer study.

The data suggest that our modern lifestyles reduce light exposure in the winter by a whopping 13 times. People’s bodily clocks went back by 2.5 hours, and the more time they spent outdoors, the earlier they went to bed at a reasonable (read: physically normal) hour. The findings are also consistent with other animal studies, showing that humans are responsive to seasonal changes in daylight. So during the winter it gets dark earlier, and the natural response of the human body is to go to sleep earlier.

Image credits: pooch_eire / Pixabay

The significance of this study, for all of us, is twofold. First of all, it shows we’re not really following our body’s natural needs. We’re going to bed too late. Secondly, it shows that if you’re going to bed too late, all you need is a short camping fix to get back to normal; about a week should do.

Delaying your natural circadian rhythm has numerous negative consequences, from reducing your day to day performance to damaging your health.

“Late circadian and sleep timing in modern society are associated with negative performance and health outcomes such as morning sleepiness and accidents, reduced work productivity and school performance, substance abuse, mood disorders, diabetes, and obesity,” says Kenneth Wright at the University of Colorado Boulder. “Our findings demonstrate that living in our modern environments contributes to late circadian timing regardless of season and that a weekend camping trip can reset our clock rapidly.”

Journal Referenc: Current Biology, Stothard and McHill et al.: “Circadian Entrainment to the Natural Light-Dark Cycle across Seasons and the Weekend” http://www.cell.com/current-biology/fulltext/S0960-9822(16)31522-6

Cramming for tests

Pulling all-nighters before tests is counter-productive – does more harm than good

The findings of a new research at UCLA, suggest that cramming all night before a big test, something that we’ve all went through at least once in a point of our lives with personal mixed results, is generally counter-productive as the sleep deprivation acts its toll on cognitive performance.

Cramming for testsWhether we’re talking about high school or university, especially the latter, we’ve all experienced situations where you postponed studying for a mid-term or homework until the last minute. Coffee soon became a much needed beacon of light as the night turned to day, and you crammed in much needed extra information for your exam. This will help you, or so you though. According to the researchers, however, regardless of how much a student generally studies each day, sacrificing a night’s sleep for extra studying hours does more harm than good.

“These results are consistent with emerging research suggesting that sleep deprivation impedes learning,” says Andrew J. Fuligni, a UCLA professor of psychiatry,

“The biologically needed hours of sleep remain constant through their high school years, even as the average amount of sleep students get declines,” he continues.

The scientists, based on their findings, advise that a consistent study schedule is best for learning, for most people at least.

Other research has shown that in 9th grade, the average adolescent sleeps for 7.6 hours per night, then declines to 7.3 hours in 10th grade, 7.0 hours in 11th grade, and 6.9 hours in 12th grade. “So kids start high school getting less sleep then they need, and this lack of sleep gets worse over the course of high school.”

The findings were published in the paper Child Development.

via KurzeweilAI . Image credit