Dangerous consequences of lack of sleep have been identified: from obesity to dementia

“We found that all forms of sleep deprivation—total sleep loss, partial sleep loss, and sleep fragmentation—lead to emotional changes. The strongest and most consistent effect was that sleep loss decreased positive mood,” says study co-author Kara Palmer, assistant professor and director of the Sleep and Development Laboratory at Montana State University in Bozeman.

“We also found that sleep loss increases anxiety,” Palmer notes. – When experiencing emotional events, people were also more likely to report that they responded differently than people who were well rested. Specifically, they reported feelings of less emotional arousal that occur when we sense the intensity of certain emotions in our body, suggesting that overall people felt more muted emotional responses after sleep loss.”

According to the US Centers for Disease Control and Prevention, adults over 18 need at least seven hours of good sleep a night to be healthy. When they fall short of this minimum, the consequences can be severe: Research has linked poor sleep to an increased risk of obesity, heart disease and dementia, as well as mood disorders, CNN reports.

A 2022 study found that despite the risks, more than 30% of adults are sleep-deprived—more than an hour of sleep less than your body needs—while nearly 1 in 10 adults are missing two or more hours of sleep each day. hours every night.

“Across the world, people rarely get the recommended amount of sleep of at least 5 nights a week,” says study co-author Joe Bower, a lecturer at the University of East Anglia in Norwich. “Our work shows the potential consequences of this for our emotional health at a time when mental health problems are rising rapidly.”

Published Thursday in the American Psychological Association’s journal Psychological Bulletin, the study analyzed data from 154 studies of more than 5,000 people over five decades.

In these studies, researchers disrupted participants’ sleep for one or more nights by either keeping them awake (sleep deprivation), periodically waking them up (sleep fragmentation), or forcing them to get up earlier than usual (partial sleep loss). Participants were then tested on anxiety, depression, mood, and their reactions to emotional triggers.

“Typically, total sleep loss had a greater impact on mood and emotions compared to partial sleep loss or fragmented sleep,” Palmer states. “Interestingly, however, the effect of sleep on positive mood occurred even after short periods of sleep deprivation, such as going to bed an hour or two later than usual or after losing just a few hours of sleep.”

The “large and comprehensive” meta-analysis highlights the strong connection between mental health and sleep, said sleep specialist and pulmonologist Dr. Raj Dasgupta, assistant professor of clinical medicine at the Keck School of Medicine of the University of Southern California. He did not take part in the study.

“There may be some truth to the saying ‘waking up on the wrong side of the bed,’ says Dr. Dasgupta. ‘Studies included in the meta-analysis found that subjects who had poor sleep quantity and quality reported that “felt more tense, angry, sad and mentally exhausted. When subjects resumed normal sleep, they reported a dramatic improvement in their mood.”

What is it about sleep that causes our body to behave this way? The answers lie in the brain, explains Kara Palmer.

“We know from previous research that sleep loss affects neural circuits involved in reward or positive experiences, which likely plays a role,” she says. “We also see increased responses in areas of the brain that are involved in the experience of emotion. At the same time, connections between our emotional centers of the brain and the prefrontal cortex, which help us properly control our emotional reactions, are disrupted.”

While all types of sleep disorders affected mood, the study found that reactions to emotional distress were more negative after loss of rapid eye movement (REM) sleep compared to loss of slow-wave or “deep” sleep.

During slow-wave sleep, the body removes potentially harmful substances from the brain, including beta-amyloid protein, a hallmark of Alzheimer’s disease, while REM sleep is the stage of sleep during which we dream and information and experiences are consolidated and stored in the brain. memory.

“Both are probably important, but in different ways,” says Joe Bauer. “For example, previous work has shown that REM sleep may be associated with the processing of emotional memories and thus may influence mood through cognitive processes.”

However, slow-wave sleep may be linked to the brain’s reward centers, which can influence responses to positive emotional situations, she said.

Deep sleep is considered one of the best indicators of sleep quality because to achieve it, a person typically must have relatively uninterrupted sleep. Because each sleep cycle is approximately 90 minutes long, most adults require seven to eight hours of relatively uninterrupted sleep to achieve restorative sleep, according to the CDC.

Sleep loss also worsened symptoms of anxiety and depression, even in people without known mental or physical disorders, according to the study.

“Longer periods of wakefulness led to more severe symptoms of depression or anxiety,” says Palmer. “It is likely that sleep loss may have different effects on people who are already depressed or have a genetic risk of developing depression.” For example, some of our previous work suggests that people who are already anxious may experience an exaggerated response to sleep loss.”

Difficulty sleeping may also be one of the first signs of a developing mental disorder, says Dr. Dasgupta.

“Chronic insomnia can increase a person’s risk of developing a mood disorder such as depression or anxiety,” he said. – Lack of sleep can be an even greater risk factor for anxiety. The studies included in the meta-analysis show that people with insomnia were more likely to develop an anxiety disorder and that insomnia is also a strong predictor of depression.”

Obstructive sleep apnea, in which the body can stop breathing for 10 seconds or more at a time, can also lead to fragmented and disturbed sleep, Dasgupta said. This type of sleep disorder is “more common in people with mental health conditions and requires treatment,” he said.

More research is needed to determine the impact of poor sleep on people with existing mental health conditions, adolescents and children, but each person should be careful in prioritizing sleep in their life, Bauer notes.

“Giving yourself time to sleep is an important act of self-care, just like eating right and exercising,” explains Joe Bauer. “It’s also important that we make systemic changes that support people’s ability to get quality sleep. This includes considering policies regarding school start times, work hours, shift patterns, and access to health care that supports treatment of sleep problems.”