Sleep Research News -- November 2020

Sleep for Joy

Most people know that not getting enough sleep can lead to an irritable day. Now a study has shown a lack of sleep sucks the joy out of life.

“Even minor night-to-night fluctuations in sleep duration can have consequences in how people respond to events in their daily lives,” said psychologist Nancy Sin from the University of British Columbia in Vancouver.

She, along with her team, used survey data from nearly 2,000 adults between the ages of 33-84. For eight consecutive days participants were asked about their sleep duration, daily stresses, and experiences of positive and negative events, according to a Sept. 16 online article on ScienceAlert.

“When people experience something positive, such as getting a hug or spending time in nature, they typically feel happier that day,” Sin said. “But we found that when a person sleeps less than their usual amount, they don’t have as much of a boost in positive emotions from their positive events.”

On the other hand, more sleep makes good events seem even better and protects against daily stress. People with chronic health problems, such as chronic pain, also had better responses with more sleep.

The research was published online Sept. 7 in Health Psychology, a journal by the American Psychological Association.

Why We Sleep

Sleep performs a number of important functions for life, but scientists often have wondered why we spend so much of our lives sleeping. 

A new study has found that the main reason for sleep changes between infancy and right before the age of 3.

For years, scientists have debated two theories about the main function of sleep. One theory suggests the brain uses sleep to organize connections between its cells and develop networks that support memory and learning. The other theory says sleep’s most important job is to clear the metabolic waste that builds up throughout the day. 

This study, published Sept. 18 in the journal Science Advances, found that infants spent most of their time in deep REM sleep, which lends itself to building new connections between brain cells. When the children in the study reached the age of 2 ½ the amount of time spent in REM sleep decreased and the brain moved into maintenance mode, according to a Sept. 22 Live Science article.

“It was definitely shocking to us that this transition was so sharp,” said senior author Van Savage, a professor of ecology, evolutionary biology and computational medicine at the University of California, Los Angeles and the Santa Fe Institute in New Mexico.

The researchers used existing data from more than 60 studies to compile several hundred data points on newborns and children up to the age of 15. They then built a mathematical model to track data points through time and see what patterns emerged, the article said. In the future, they plan to use their mathematical model to track sleep in animals to see if a similar shift occurs.

“Humans are known to be unusual in the amount of brain development that occurs after birth,” said lead author Junyu Cao, an assistant professor in the Department of Information, Risk and Operations Management at The University of Texas at Austin. “Therefore, it is conceivable that the phase transition described here for humans may occur earlier in other species, possibly even before birth.”

Another Strike Against Light Pollution

Light pollution from big cities blocks out starry skies — and also messes with teenagers’ sleep.

A study published July 5 in the journal JAMA Psychiatry collected data on mental health issues and sleep patterns from more than 10,000 teens participating in the National Comorbidity Survey Adolescent Supplement. Researchers from the National Institute of Mental Health in Bethesda, Maryland, and other organizations found that youths who lived in areas with high levels of outdoor light went to bed later and slept less. They also were more likely to be diagnosed with bipolar disorder or a specific phobia, according to a July 8 article on CNN.

“Although environmental light exposure is only one factor in a more complex network of influences on sleep and behavior, it is likely to be an important target for prevention and interventions in adolescent health,” said co-author Kathleen Merikangas, a senior investigator and chief of the Genetic Epidemiology Research Branch at the National Institute of Mental Health.

Naps No Substitute for Good Night’s Sleep

A nap when you slept poorly the night before can be a good thing. Relying on daily naps to make up for chronic sleep deprivation is not, according to a U.S. Army study.

The study, published Sept. 2 in Nature Communications, found the brain is better at flushing out toxins during nighttime sleep.

“These findings suggest that people who rely on catnaps during the day to catch up on sleep or work the night shift may be at risk for developing neurological disorders,” said Lauren Hablitz, lead author of the study and research assistant at the Center for Translational Neuromedicine at the University of Rochester Medical Center in Rochester, New York.

“In fact, clinical research shows that individuals who rely on sleeping during daytime hours are at much greater risk for Alzheimer’s and dementia, along with other health problems,” she said.

Higher BMI Linked to Shorter Sleep

Want to keep your weight under control? Get some rest.

Studies have shown that a lack of sleep leads to weight gain. When a person is sleep deprived, levels of the hormone ghrelin — responsible for an increase in hunger —spike and another hormone, leptin — which suppresses appetite — drops, according to a Sept. 14 article on CNN.

A new study has confirmed that poor sleep is connected with a greater body mass index. While previous studies have relied on people reporting how much they slept, this study used sleep apps on fitness trackers, smartphones and watches to track sleep quality in 120,000 people for up to two years. 

Published Sept. 14 in JAMA Internal Medicine, the study done by researchers in La Jolla, California, found that individual sleep patterns were highly variable. People with BMIs of 30 and above, which is considered obese by the U.S. Centers for Disease Control and Prevention, slept 15 minutes less than those with lower BMIs and had more variable sleep patterns. 

Chemicals Disrupt Rest 

Women in midlife often experience sleep difficulties. Some can be attributed to changing hormones and daily stressors. A new study now points to an additional cause — environmental chemicals. 

Exposure to endocrine-disrupting chemicals, such as phthalates, seems to have an impact on sleep in menopausal women.

According to a July 29 article on Medical Xpress, phthalates are found in industrial plasticizers and chemical stabilizers. The chemicals often are used in personal care products.

Even though many people are exposed to them, phthalates concentrate more in women than men, the study found. “This study is important because endocrine-disrupting chemicals are everywhere,” said Stephanie Faubion, a women’s health physician at the Mayo Clinic in Jacksonville, Florida, and the medical director for The North American Menopause Society. “It provides additional evidence of potential sex differences in endocrine-disrupting chemical exposure (in this case, phthalates) and impact on health.”

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