Breakthrough research shows the brain doesn’t drift into sleep gradually; it hits a sudden “tipping point.” Discover how scientists pinpoint the second your brain shuts down each night
Groundbreaking UKRI-funded research has unveiled a startling revelation: falling asleep isn’t a gradual process, but a sudden switch. By analysing EEG data from over 1,000 individuals, scientists can now predict the exact moment of sleep onset with an astonishing 98 % accuracy. This discovery has the potential to revolutionise our understanding of sleep, enhance treatments for insomnia, and safeguard brain health.
The findings are detailed in Nature Neuroscience.
Monitoring the transition from wakefulness to sleep
The researchers adopted a novel computational method that represents changes in the brain in a multidimensional space and maps how each moves from bedtime toward sleep. The team analysed electroencephalogram (EEG) recordings from more than 1,000 people who wore electrodes to monitor their brain activity overnight.
The researchers found that, regardless of how long participants were in bed, the transition from wakefulness to sleep occurred abruptly in the final few minutes, at a clear tipping point.
This is called ‘bifurcation’, a term from mathematics and physics, which is an example of the gradual bending of a stick until it eventually snaps. It also resembles the movement of a falling object, thereby supporting the subjective sensation of ‘falling asleep’.
In a different experiment involving recordings over multiple nights, they discovered that each participant had a unique location in the multi-dimensional space where sleep began. This ‘multi-dimensional space’ is a mathematical representation of the brain’s activity, and the ‘unique location’ refers to a specific pattern of brain activity that signals the onset of sleep.
This was consistent across multiple nights of sleep.
Predicting the moment participants fall asleep
The researchers showed they could predict with 98% accuracy the exact progression, second by second, of when each participant fell asleep. This approach is the first time scientists have been able to objectively infer the precise momentary progression and exact point at which the brain falls asleep.
Previously, the onset of sleep was determined by subjective reports of brain activity from EEG recordings or by indirect measures such as heart rate, breathing rate, and movement.
The implications of these findings are far-reaching. They could pave the way for innovative methods to diagnose and treat sleep disorders, serve as a crucial marker of brain health in neurodegenerative diseases, and enhance anaesthesia monitoring. This breakthrough offers a ray of hope for those struggling with sleep-related issues.
Dr Karen Brakspear, Head of Neurosciences and Mental Health at MRC, said: “Sleep disturbances are increasingly recognised as a risk factor for neurodegenerative disease such as Alzheimer’s disease.
By gaining a deeper understanding of the brain’s transition into sleep, we can potentially unlock the intricate connections between sleep and dementia. This could lead to the development of novel strategies to foster healthy sleep, offering a beacon of hope in the fight against neurodegenerative diseases.
MRC-funded study leader Dr Nir Grossman, Group Leader at the UK DRI at Imperial College London, said: “Sleep is a fundamental part of our lives. The process of falling asleep is the critical gateway to the vital physiological and cognitive benefits of sleep.
Yet, how our brain falls asleep has been one of the most enduring mysteries of neuroscience.
In this study, we presented a method that enables us, for the first time, to track in real-time how the brain transitions into sleep with unprecedented precision.
We discovered that falling asleep is a bifurcation, not a gradual process, with a clear tipping point that can be predicted in real time.
The ability to track how individual brains fall asleep has profound implications for our understanding of sleep.
It also serves as a vital health marker for changes in the brain, due to factors such as ageing or the development of brain diseases like dementia.
Significantly, it could facilitate the development of new treatments for people who struggle with falling asleep.”
Senior co-author Professor Derk-Jan Dijk, Group Leader at the UK DRI Centre for Care Research and Technology at Imperial College London and the University of Surrey, said:
“Our experiments demonstrate that by analysing brain waves through a ‘dynamical system’ lens, we can generate new insights into how sleep really works, going far beyond what standard sleep scoring reveals.
This study has the potential to transform how we clinically define the beginning of sleep.
It is commonly believed that falling asleep is a gradual, continuous process, but we have identified that it is in fact an abrupt transition, with a tipping point at which the brain moves from a waking state into sleep.
Understanding and harnessing this will enable us to better study the biology underpinning the process of falling asleep, and inform the development of new diagnostic tools and therapies.”
