The hypothesis, which was detailed in a recent paper in Frontiers in Network Psychology, suggests that when humans are awake during the biological circadian night – after midnight for most people – there are neurophysiological changes in the brain that alter the way we interact with the world, especially actions related to reward processing, impulse control and information processing.
These changes can make you more likely to view the world negatively, engage in harmful behaviors, and make impulsive decisions (including those associated with addictive behaviors such as gambling and substance abuse) without fully thinking through the consequences.
Klerman describes the hypothesis as a call for researchers to conduct new studies to better understand how these circadian differences affect behavior, decision making and job performance at night—and identify strategies that can help people cope.
The findings could have wide-ranging effects on individuals who are required to be awake at night for work, including pilots, health care workers, police officers and military personnel. Research could also lead to new strategies to reduce violent crime, substance use disorders, suicides and other harmful behaviors.
“There are millions of people who are awake in the middle of the night, and there’s fairly good evidence that their brain is not functioning as well as it does during the day,” Klerman says. “My plea is for more research to look at that, because their health and safety, as well as that of others, is affected.”
Bad things happen after dark
For example, Michael L. Perlis, Ph.D., an Associate Professor of Psychology at UPenn’s Perelman School of Medicine and a co-author of the Mind After Midnight hypothesis, found that if you adjust for the number of people who are awake at any given time, suicides are statistically more likely to occur during the nighttime hours.
Homicides and violent crime are also more common at night, as are the risks of the illicit or inappropriate use of substances such as cannabis, alcohol and opioids.
Our nighttime food choices at night also tend to be unhealthy, as we pursue more carbohydrates, lipids and processed foods and often consume more calories than we need.
So why is it that all these bad behaviors come out at night?
There are a few obvious answers—it’s much easier to commit a crime under the cover of darkness, for one, and there are less people around and awake at night to help us keep our behavior in check. But it’s likely there’s a biological basis as well.
Klerman explains that the circadian influence on the neural activity in our brains changes over the course of 24 hours, leading to differences in the way we process and respond to the world.
For example, positive affect—the tendency to view information in a positive light—is at its highest point during the morning, when circadian influences are tuned to wakefulness, and at its lowest point during the night, when circadian influences are tuned to sleep.
In parallel, negative affect—the tendency to view information in a negative or threatening light is highest at night.
Your body also naturally produces more dopamine at night, which can alter your reward and motivation system and increase the likelihood of engaging in risky behavior.
This biased interpretation of information is then sent along to the parts of the brain responsible for decision-making, which normally work to control negative emotional distractions and focus on goal-oriented behavior.
But these parts of the brain are also subject to circadian-influenced changes that can impair decision making, functioning and prioritization.
Suddenly, your worldview narrows and becomes more negative, you start to make poor decisions, and the mental map you create of the world around you may no longer match up with reality.
The result? You might end up drinking too much, missing a crucial diagnosis on a patient, crashing an oil tanker into some rocks, or worse.
Klerman experienced some of these feelings firsthand when she struggled to fall asleep after experiencing severe jet lag during a trip to Japan.
“While part of my brain knew that eventually I would fall asleep, while I was lying there and watching the clock go tick tick tick—I was beside myself,” she recalls.
“Then I thought, ‘What if I was a drug addict? I would be out trying to get drugs right now.’ Later I realized that this may be relevant also if it’s suicide tendencies, or substance abuse or other impulse disorders, gambling, other addictive behaviors. How can I prove that?”
Putting the hypothesis to the test
The need for proof is key here. It’s important to note that Mind After Midnight is still a hypothesis—one that will require validation through carefully constructed research studies.
In an ironic twist, the best way to gather this data without the confounding effects of sleep loss will require researchers and study staff themselves to be awake and working after midnight, for example by taking fMRI images of study participants whose sleep cycles have been carefully adjusted for nighttime wakefulness or conducting other protocols.
“Most researchers don’t want to be paged in the middle of the night. Most research assistants and technicians don’t want to be awake in the middle of the night,” Klerman concedes.
“But we have millions of people who have to be awake at night or are awake at night involuntarily. Some of us will have to be inconvenienced so we can better prepare them, treat them, or do whatever we can to help.”
Sleep is an important time for the brain. Levels of brain activity change in each stage of sleep — including both rapid eye movement (REM) and non-REM (NREM) sleep — and evidence increasingly suggests that sleep enhances most types of cognitive function.
Getting enough hours of high-quality sleep fosters attention and concentration, which are a prerequisite for most learning. Sleep also supports numerous other aspects of thinking including memory, problem-solving, creativity, emotional processing, and judgment.
For people with sleep deprivation, insomnia, sleep apnea, or other conditions that prevent getting adequate rest, short-term daytime cognitive impairment is common. In addition, multiple studies have linked poor sleep with longer-term cognitive decline, including the development of dementia and Alzheimer’s dementia.
Thankfully, there is evidence that improving sleep can boost both short- and long-term cognitive performance. Better sleep can promote sharper thinking and may reduce the likelihood of age-related cognitive decline.
What Happens to the Brain During Sleep?
During a typical night of sleep, an individual goes through four to six sleep cycles1 that range from 70 to 120 minutes each. Both the brain and body experience distinct changes2 during these cycles that correspond to individual stages of sleep.
During NREM stages, brain activity slows overall, but there remain pulses of specific types of brain waves. This pattern of brain waves is most pronounced in stage 3 NREM sleep, which is also known as slow-wave sleep or deep sleep.
In contrast, REM sleep is marked by a sizable uptick in brain activity. In many ways, the brain’s activity during REM sleep is similar to when you’re awake. Not surprisingly, REM sleep is known for more vivid and involved dreaming.
It’s normal to cycle through both NREM and REM stages, with REM sleep being more concentrated in the second half of the night. During each part of this process, different chemicals in the brain become activated or deactivated to coordinate rest and recovery.
Experts still aren’t exactly certain why sleep proceeds in this pattern, but it is believed that it facilitates mental recovery3, which can unlock cognitive benefits related to attention, thinking, and memory.
How Poor Sleep Affects the Brain
Without sleep, the brain struggles to function properly. Because they don’t have time to recuperate, neurons become overworked4 and less capable of optimal performance in numerous types of thinking.
Poor sleep can take many forms. It can be caused by short sleep duration and/or fragmented sleep. Both insufficient and interrupted sleep make it difficult to progress through sleep cycles in a normal, healthy way.
The short-term implications of poor sleep on the brain and cognition can be the result of simply pulling an all-nighter, while those with chronic sleep problems may see their day-to-day tasks affected. Over the long-term, however, poor sleep may put someone at a higher risk of cognitive decline and dementia.
What Are the Short-Term Impacts of Poor Sleep on Cognition?
The potential short-term impacts of sleep on cognitive performance are wide-ranging.
Most people are familiar with the daytime effects that result from a night of poor sleep, such as drowsiness and fatigue. In response, a person may inadvertently nod off for a few seconds, which is known as a microsleep5.
While a night of disrupted sleep may be inconvenient, the resulting daytime sleepiness can cause serious cognitive impairments. It reduces a person’s attention, as well as their learning and processing. A lack of sleep has also been found to induce effects that are similar to being drunk6, which slows down thinking and reaction time.
Just struggling to stay alert can, in itself, cause sweeping problems for thinking, but research also indicates that there are selective impacts of poor sleep on mental function7. This means that insufficient or disrupted sleep causes more harm to certain parts of the brain with distinct effects on different types of cognition8.
Studies of the selective impact of sleep on types of thinking do not always generate consistent results. This may be the result of differences in the people in the studies, how their sleep is changed in the research, or how cognitive effects are measured. Nevertheless, there are some general findings about ways that poor sleep may impair intellectual performance.
There are strong indications that sleep and memory are closely linked. Lack of sleep hinders working memory, which is necessary to remember things for immediate use.
Both NREM and REM sleep appear to be important for broader memory consolidation9, which helps reinforce information in the brain so that it can be recalled when needed. For example, NREM sleep has been linked with formation of declarative memory, which includes things like basic facts or statistics, and REM sleep is believed to boost procedural memory such as remembering a sequence of steps.
Poor sleep impairs memory consolidation by throwing off the normal process that draws on both NREM and REM sleep for building and retaining memories. Studies have even found that people who are sleep deprived are at risk of forming false memories10. Fragmented sleep has also been found to negatively affect memory11 even if a person gets plenty of total hours of sleep.
On top of the consequences for memory, poor sleep detracts from other cognitive tasks. It diminishes placekeeping12, which includes the ability to carry out instructions. Motor skills, keeping rhythm, and even some types of speech are worsened without proper sleep.
Some studies have found lack of sleep to hinder cognitive flexibility13, reducing the ability to adapt and thrive in uncertain or changing circumstances. A major reason this occurs is rigid thinking and “feedback blunting”14 in which the capacity to learn and improve on-the-fly is diminished.
Another way that poor sleep impairs thinking is by altering how emotional information is understood15. When learning something new, analyzing a problem, or making a
decision, recognizing the emotional context is often important. However, insufficient sleep — which frequently affects mood16 — impedes the ability to properly process this emotional component of information.
In many cases, this disrupted emotional response impairs judgment. People who don’t get sufficient sleep are more likely to make risky choices17 and to focus on a potential reward rather than downsides. This can become negatively reinforcing because a lack of sleep limits our ability to learn from these mistakes since the normal method of processing and consolidating emotional memory is compromised.
Creativity is another aspect of cognition that is harmed by sleeping problems. Connecting loosely associated ideas is a hallmark of creativity, and this ability is strengthened by good sleep18. NREM sleep provides an opportunity for information to be restructured and reorganized19 in the brain, while new ideas and links between thoughts often emerge during REM sleep20. These processes enable insight, a core element of innovation and creative problem-solving.
Limited or restless sleep can also indirectly affect cognition because of other problems that they cause. For example, migraine sufferers are more likely to have morning headache attacks21 when they don’t get enough sleep, and lack of sleep can increase the risk of the infections22 like the common cold. Sleep deprivation may worsen symptoms of mental health conditions like anxiety and depression. These and numerous other physical and mental health issues are shaped by the quality of our sleep, and may affect a person’s attention and concentration.
The existing research strongly supports the notion that poor sleep detracts from effective thinking. Without quality sleep, people are more likely to make errors, fail to take in new information, suffer deficits in memory, or have impaired decision-making.
As a result, poor sleep can harm intellectual performance, academic achievement, creative pursuits, and productivity at work. The cognitive impacts of poor sleep can also create health risks, including life-threatening dangers from drowsy driving or operating heavy machinery without adequate sleep.
What Are the Long-Term Impacts of Poor Sleep on Cognition?
The most obvious cognitive effects of poor sleep can be felt immediately, but mounting evidence shows that sleep influences the long-term risks of cognitive decline and dementia.
An analysis of more than 25 observational studies found a considerably higher risk of cognitive impairment and Alzheimer’s dementia23 in people with sleep problems. In fact, that analysis estimated that as many as 15% of cases of Alzheimer’s dementia are attributable to poor sleep.
Research shows that sleep helps the brain conduct important housekeeping, such as clearing out potentially dangerous substances like beta amyloid proteins. In Alzheimer’s dementia, beta amyloid forms in clusters, called plaques, that worsen cognitive function. Studies have found that even one night of sleep deprivation can increase the amount of beta amyloid in the brain24.
This is one possible explanation for why insufficient sleep and sleep fragmentation25 have been associated with cognitive decline and dementia. Furthermore, in people already diagnosed with dementia, poor sleep has been linked to a worse disease prognosis26.
Are the Impacts of Poor Sleep on Thinking the Same For Everyone?
Not everyone is affected by poor sleep in the same way. Studies have found that some individuals may be more inclined to have cognitive impairment from sleep deprivation, and this may even have a genetic component.
Research has generally discovered that adults are better at overcoming the effects of sleep deprivation than younger people. Teens are considered to be especially high-risk for detrimental effects of poor sleep on thinking, decision-making, and academic performance27 because of the ongoing brain development occurring during that age.
Some studies have also found that women are more adept at coping with the effects of sleep deprivation than men, although it is not yet clear if this is related to biological factors, social and cultural influences, or a combination of both.
Can Sleep Disorders Affect Cognition?
Sleep disorders frequently involve insufficient or fragmented sleep, so it comes as little surprise that they can be linked to cognitive impairment.
Insomnia, which can involve problems with both falling asleep and staying asleep through the night, has been connected to both short- and long-term cognitive problems.
Obstructive sleep apnea (OSA) is another one of the most common sleep disorders. It occurs when the airway gets blocked, which then leads to lapses in breathing during sleep and reduced oxygen in the blood.
OSA has been linked with daytime sleepiness as well as notable cognitive problems28 related to attention, thinking, memory, and communication. Studies have also found that people with sleep apnea have a higher risk of developing dementia29.
reference link :https://www.sleepfoundation.org/sleep-deprivation/lack-of-sleep-and-cognitive-impairment
More information: Andrew S. Tubbs et al, The Mind After Midnight: Nocturnal Wakefulness, Behavioral Dysregulation, and Psychopathology, Frontiers in Network Physiology (2022). DOI: 10.3389/fnetp.2021.830338
