Researchers have known for a while about a connection between insufficient sleep and anxiety. A new study strengthens and quantifies this causal relation and shows that a sleepless night can raise anxiety by up to 30 per cent. Furthermore, the new study suggests that the deep phase of sleep is a natural anxiety reliever. These are the main takeaways of a paper appearing in the journal Nature Human Behaviour.
Matthew Walker, a professor of neuroscience and psychology at the University of California (UC), Berkeley, is the senior author of the new study. Prof. Walker and colleagues set out to examine the effects of various stages of sleep on anxiety in 18 participants.
Scientists routinely divide sleep into two broad categories — rapid eye movement (REM) and non-REM sleep — and four sub-stages. The first two stages of non-REM sleep are periods of light sleep in which the body adjusts from wakefulness to rest.
According to the National Institutes of Health (NIH), the third stage of non-REM sleep is the deep, restorative sleep that we need to feel recharged in the morning. REM sleep, which is the dream-filled, the lighter stage before waking, and typically follows Non-REM sleep.
These different sleep stages reflect differently in the brain’s activity. By measuring brain activity, Prof. Walker and the team determined the effects of various sleep stages on anxiety. To measure anxiety levels, the researchers asked a group of 18 young adults to watch emotionally unsettling videos after a full night of sleep and after a sleepless night.
After each viewing, the participants completed a standard anxiety questionnaire called the state-trait anxiety inventory. We look at the effects of sleep deprivation, as well as ways of reducing stress. The scientists used functional Magnetic Resonance Imaging (MRI) and polysomnography to scan the brains of the sleeping participants in order to identify the stages of sleep.
The brain scans showed that a brain area called the medial prefrontal cortex was deactivated after a sleepless night. Previous studies have suggested that this brain area attenuates anxiety and stress. The scans also revealed excessive brain activity in other regions associated with processing emotions. A sleepless night raised anxiety levels by up to 30%, report the authors.
“Without sleep,” Prof. Walker explains, “it’s almost as if the brain is too heavy on the emotional accelerator pedal, without enough brake.” Furthermore, the study found that anxiety levels plummeted after a full night of sleep and that this reduction was even more significant in people who spent more time in the deep, slow-wave, non-REM stage of sleep.
“Deep sleep had restored the brain’s prefrontal mechanism that regulates our emotions, lowering emotional and physiological reactivity and preventing the escalation of anxiety,” reports Eti Ben Simon, a postdoctoral fellow at the Center for Human Sleep Science at UC Berkeley and the study’s lead author.
The researchers sought to replicate their findings, so they conducted another set of experiments in a larger sample, of 30 participants, as well as an online survey, of 280 people.
The lab experiments confirmed that people who experienced more deep sleep at night had the least anxiety the following day. The online survey confirmed that the amount and quality of sleep that people got reliably predicted their anxiety levels the following day.
The study’s lead author also suggests that good sleep should be a clinical recommendation for treating anxiety. “People with anxiety disorders routinely report having disturbed sleep, but rarely is sleep improvement considered as a clinical recommendation for lowering anxiety,” she says.
“Our study not only establishes a causal connection between sleep and anxiety, but it identifies the kind of deep [non-] REM sleep we need to calm the overanxious brain.”
The study’s senior author also comments on the findings, saying, “We have identified a new function of deep sleep, one that decreases anxiety overnight by reorganizing connections in the brain.” “Deep sleep seems to be a natural anxiolytic (anxiety inhibitor), so long as we get it each and every night,” concludes Prof. Walker.
Meanwhile, people who have trouble sleeping may be more likely to have a stroke, heart attack or other cerebrovascular or cardiovascular diseases, according to a study published in the November 6, 2019, online issue of Neurology, the medical journal of the American Academy of Neurology.
“These results suggest that if we can target people who are having trouble sleeping with behavioral therapies, it’s possible that we could reduce the number of cases of stroke, heart attack and other diseases later down the line,” said study author Liming Li, MD, of Peking University in Beijing, China.
The study involved 487,200 people in China with an average age of 51. Participants had no history of stroke or heart disease at the beginning of the study.
Participants were asked if they had any of three symptoms of insomnia at least three days per week: trouble falling asleep or staying asleep; waking up too early in the morning, or trouble staying focused during the day due to poor sleep. A total of 11 percent of the people had difficulty falling asleep or staying asleep; 10 percent reported waking up too early, and two percent had trouble staying focused during the day due to poor sleep. The researchers did not determine if the people met the full definition of insomnia.
The people were then followed for an average of about 10 years. During that time, there were 130,032 cases of stroke, heart attack, and other similar diseases.
People who had all three symptoms of insomnia were 18 percent more likely to develop these diseases than people who did not have any symptoms. The researchers adjusted for other factors that could affect the risk of stroke or heart disease including alcohol use, smoking, and level of physical activity.
People who had trouble falling asleep or staying asleep were 9 percent more likely to develop stroke or heart disease than people who did not have this trouble. Of the 55,127 people who had this symptom, 17,650, or 32 percent, had a stroke or heart disease, compared to 112,382, or 26 percent, of the 432,073 people who did not have this symptom of insomnia.
People who woke up too early in the morning and could not get back to sleep were seven percent more likely to develop these diseases than people who did not have that problem. And people who reported that they had trouble staying focused during the day due to poor sleep were 13 percent more likely to develop these diseases than people who did not have that symptom.
“The link between insomnia symptoms and these diseases was even stronger in younger adults and people who did not have high blood pressure at the start of the study, so future research should look especially at early detection and interventions aimed at these groups,” Li said.
Li noted that the study does not show cause and effect between the insomnia symptoms and stroke and heart disease. It only shows an association.
A limitation of the study was that people reported their own symptoms of insomnia, so the information may not have been accurate. Also, the researchers did not ask participants about having sleep that was not refreshing; this is another common symptom of insomnia.make a difference: sponsored opportunity.
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