Revolutions is a series that brings together a hand-picked selection of recent articles canvassing cutting-edge insights into major scientific advances. This installment brings you up to date with the ground-breaking new discoveries made in the science of sleep.

We all intimately understand how important sleep is in maintaining well-being and health. Have a couple of bad nights and pretty quickly you'll feel irritable, cranky and unwell. It is clear humans spend one third of their life asleep for a fundamental reason, and while scientists have slowly learned more and more about what our bodies are doing while we sleep, there is still so much about sleep that remains a mystery.

We know sleep consists of several different phases (from REM to slow-wave) and we also know our circadian clock regulates daily sleep cycles. But why is our need for sleep so profound? And what chronic diseases might be caused by sleep disruptions?

Recent scientific discoveries have revealed sleep may be more important for our health than we previously imagined. From depression and weight gain, to dementia and Alzheimer's disease, here is a rapid rundown of the latest things we have learned about sleep, and it suggests concentrating on getting a solid eight hours a night could be one of the most important things you can do for your overall health.

Too much sleep is just as bad for your brain as too little

Late in 2018 the first results from the world's largest sleep study were published and they revealed more sleep in not necessarily better. The study found between seven and eight hours of sleep was the optimal range for a healthy adult. Subjects in the study that slept more than eight hours tended to display similar cognitive impairments to those that slept less than seven hours. So unless you are a teenager, sleeping ten hours a night may be just as unhealthy as sleeping for six hours. Read more

Alzheimer's and Dementia

Clinicians have long seen an association between age-related cognitive decline and disrupted sleep. Some of the most revelatory recent sleep science has uncovered a potential causal relationship that suggests bad sleep could actually be contributing to the onset of Alzheimer's disease. The two toxic proteins most commonly associated with neurodegenerative diseases have been found to be directly driven by sleep deprivation. Read more

Perhaps most striking was a recent study that specifically homed in on the sleep phase responsible for clearing the brain of toxic amyloid and tau proteins. It was revealed that slow-wave sleep is the phase most effective at clearing waste from the brain. A separate study into humans suffering from sleep apnea affirmed those subjects unable to consistently enter deep slow wave sleep seemed to display higher tau protein accumulations in the brain. Read more

How sleep repairs damaged DNA in the brain

Using a high-resolution microscope that allowed researchers to observe chromosome activity within a single neuron in zebrafish, it was recently revealed that the DNA damage that accumulates in neurons during waking hours is efficiently repaired during sleep. When this natural sleep-wake rhythm is disrupted, excess DNA damage can accumulate in a neuron. What this all means is still unknown, but it suggests a fundamental importance to sleep that explains why every animal on the planet has evolved this process. Read more

Two massive genetic studies zero in on the origins of insomnia

Insomnia may feel like a purely psychological condition, a side-effect of depression, anxiety or stress. However, an interesting body of research is beginning to indicate the condition may be fundamentally underpinned by genetic triggers.

One of the most interesting findings from this new research was a lack of genetic overlap between insomnia and other sleep-related traits. It seems the genetic underpinning of insomnia is more related to psychiatric conditions such as depression and anxiety. This compelling discovery suggests prior work investigating insomnia treatments that target sleep-regulating brain areas may have been looking in the wrong place. Read more

Newly discovered mechanism connects depression and bad sleep

A 2018 study from a team of international researchers found a unique neurological mechanism underlies the oft-seen association between depression and sleep disruption. The results revealed that those suffering from depression and bad sleep displayed unusually increased connectivity between three different brain regions: the dorsolateral prefrontal cortex, the precuneus, and the lateral orbitofrontal cortex. The hypothesis is that bad sleep is not a symptom of depression, but the two are much more fundamentally intertwined. Read more

The weird connection between sleep and hydration

A study from researchers at Penn State has revealed a new reason why getting less than the recommended eight hours of sleep a night could be damaging to our health. The research found adults who only got around six hours of sleep per night were more likely to be dehydrated, and the cause could be a particular hydration-regulating hormone that is released late in a person's sleep cycle. Read more

How sleep loss leads to weight gain

What if the frequent connection between bad sleep and weight gain was not simply due to eating junk food late at night? What if sleep loss actually results in more direct metabolic alterations at a tissue level? A study from Uppsala University identified two separate metabolic mechanisms that were triggered following sleep deprivation. Taken together, these two processes could underpin how sleep disruptions can cause both a gain in fat mass and a loss of lean muscle. Read more

Bad news night-owls: Staying up late could be killing you

Are you a night owl or a morning lark? Some people naturally gravitate to staying up late, and while genetics do play a major role in establishing your body clock, some research is suggesting later bedtimes could be bad for your health. A new large-scale observational study involving data from nearly half a million people has found that night owls have a 10 percent higher risk of dying sooner than those with a preference for getting to bed early. Read more

Another study, from scientists at the University of Colorado Boulder, studied how protein levels in human blood can vary over a 24-hour period depending on when a person is sleeping and eating. The striking results found that when a person stays up all night, the patterns of over 100 different proteins in the blood are disrupted. Read more

Sleep deprivation makes pain feel worse

Around 60 percent of patients suffering chronic pain also report consistent sleep disruptions. This connection is perhaps unsurprising, after all, if you are in pain it is undoubtedly difficult to sleep. But what if sleep loss was actively increasing a person's sensitivity to pain? A fascinating fMRI study showed that sleep loss not only amplifies activity in the pain sensing regions of the brain but also blocks the natural analgesia centers. Read more

Sleep and learning

We know that information acquired during waking states is imprinted on a deeper level when followed by a sleep period, but a new study from the University of Bristol has found short naps can also help a person process information they were not even consciously aware of perceiving. Read more

Another study from a team in Paris investigated the old idea of "sleep learning", the idea we can acquire new information while we are asleep. It turns out we can learn while we sleep, but it crucially depends on what phase of sleep the auditory information is delivered during. Read more

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