Adequate sleep can help prevent osteoporosis, according to a growing body of research. As part of the University of Colorado Department of Medicine’s annual Research Day, held on April 23, faculty member Christine Swanson, MD, MCR, described her clinical research on how sleep interacts with osteoporosis.
“Osteoporosis can occur for many reasons such as hormonal changes, aging, and lifestyle factors,” said Swanson, an associate professor in the Division of Endocrinology, Metabolism, and Diabetes. “But some patients I see don’t have an explanation for their osteoporosis.
“Therefore, it’s important to look for novel risk factors and consider what else changes across the lifespan like bone does – sleep is one of those,” she added.
How bone density and sleep change over time
In people’s early- to mid-20s, they reach what is called peak bone mineral density, which is higher for men than it is for women, Swanson said. This peak is one of the main determinants of fracture risk later in life.
Bone density mostly plateaus for a couple of decades. Then, when women enter the menopausal transition, they experience accelerated bone loss. Men also experience bone density decline as they age.
Sleep patterns also evolve over time. As people get older, their total sleep time decreases, and their sleep composition changes. For instance, sleep latency, which is the time it takes to fall asleep, increases with age. On the other hand, slow wave sleep, which is deep restorative sleep, decreases as we age.
“And it’s not just sleep duration and composition that change. Circadian phase preference also changes across the lifespan in both men and women,” Swanson said, referring to people’s preference for when they go to sleep and when they wake up.
How is sleep linked to bone health?
Genes that control our internal clock are present in all of our bone cells, Swanson said.
“When these cells resorb and form bone, they release certain substances into the blood that let us estimate how much bone turnover is going on at a given time,” she said.
These markers of bone resorption and formation follow a daily rhythm. The amplitude of this rhythm is larger for markers of bone resorption than it is for markers of bone formation, she said.
“This rhythmicity is likely important for normal bone metabolism and suggests that sleep and circadian disturbance could directly affect bone health,” she said.
Researching the connection between sleep and bone health
To further understand this relationship, Swanson and colleagues researched how markers of bone turnover responded to cumulative sleep restriction and circadian disruption.
For this study, participants lived in a completely controlled inpatient environment. The participants did not know what time it was, and they were put on a 28-hour schedule instead of a 24-hour day.
“This circadian disruption is designed to simulate the stresses endured during rotating night shift work and is roughly equivalent to flying four time zones west every day for three weeks,” she said. “The protocol also caused participants to get less sleep.”
The research team measured bone turnover markers at the beginning and end of this intervention and found significant detrimental changes in bone turnover in both men and women in response to the sleep and circadian disruption. The detrimental changes included declines in markers of bone formation that were significantly greater in younger individuals in both sexes compared to the older individuals.
In addition, young women showed significant increases in the bone resorption marker.
If a person is forming less bone while still resorbing the same amount – or even more – then, over time, that could lead to bone loss, osteoporosis, and increased fracture risk, Swanson said.
“And sex and age may play an important role, with younger women potentially being the most susceptible to the detrimental impact of poor sleep on bone health,” she said.
During a night’s sleep, the brain weakens the new connections between neurons that had been forged while awake – but only during the first half, according to a new study in fish by UCL scientists.
The researchers say that their findings, published in Nature, provide insight into the role of sleep, but still leave an open question around what function the latter half of a night’s sleep serves.
The researchers say the study supports the Synaptic Homeostasis Hypothesis, a key theory on the purpose of sleep which proposes that sleeping acts as a reset for the brain.
Lead author Professor Jason Rihel (UCL Cell & Developmental Biology) said: “When we are awake, the connections between brain cells get stronger and more complex. If this activity were to continue unabated, it would be energetically unsustainable. Too many active connections between brain cells could prevent new connections from being made the following day.
“While the function of sleep remains mysterious, it may be serving as an ‘off-line’ period when those connections can be weakened across the brain, in preparation for us to learn new things the following day.”
For the study, the scientists used optically translucent zebrafish, with genes enabling synapses to be easily imaged. The research team monitored the fish over several sleep-wake cycles.
The researchers found that brain cells gain more connections during waking hours, and then lose them during sleep. They found that this was dependent on how much sleep pressure (need for sleep) the animal had built up before being allowed to rest; if the scientists deprived the fish from sleeping for a few extra hours, the connections continued to increase until the animal was able to sleep.
Professor Rihel added: “If the patterns we observed hold true in humans, our findings suggest that this remodelling of synapses might be less effective during a mid-day nap, when sleep pressure is still low, rather than at night, when we really need the sleep.”
The researchers also found that these rearrangements of connections between neurons mostly happened in the first half of the animal’s nightly sleep. This mirrors the pattern of slow-wave activity, which is part of the sleep cycle that is strongest at the beginning of the night.
First author Dr Anya Suppermpool (UCL Cell & Developmental Biology and UCL Ear Institute) said: “Our findings add weight to the theory that sleep serves to dampen connections within the brain, preparing for more learning and new connections again the next day. But our study doesn’t tell us anything about what happens in the second half of the night. There are other theories around sleep being a time for clearance of waste in the brain, or repair for damaged cells – perhaps other functions kick in for the second half of the night.”
A new review of research evidence has explored the key differences in how women and men sleep, variations in their body clocks, and how this affects their metabolism. Published in Sleep Medicine Reviews, the paper highlights the crucial role sex plays in understanding these factors and suggests a person’s biological sex should be considered when treating sleep, circadian rhythm and metabolic disorders.
Differences in sleep
The review found women rate their sleep quality lower than men’s and report more fluctuations in their quality of sleep, corresponding to changes throughout the menstrual cycle.
“Lower sleep quality is associated with anxiety and depressive disorders, which are twice as common in women as in men,” says senior author Dr Sarah L. Chellappa from the University of Southampton. “Women are also more likely than men to be diagnosed with insomnia, although the reasons are not entirely clear. Recognising and comprehending sex differences in sleep and circadian rhythms is essential for tailoring approaches and treatment strategies for sleep disorders and associated mental health conditions.”
The paper’s authors also found women have a 25 to 50% higher likelihood of developing restless legs syndrome and are up to four times as likely to develop sleep-related eating disorder, where people eat repeatedly during the night.
Meanwhile, men are three times more likely to be diagnosed with obstructive sleep apnoea (OSA). OSA manifests differently in women and men, which might explain this disparity. OSA is associated with a heightened risk of heart failure in women, but not men.
Sleep lab studies found women sleep more than men, spending around 8 minutes longer in non-REM (Rapid Eye Movement) sleep, where brain activity slows down. While the time we spend in NREM declines with age, this decline is more substantial in older men. Women also entered REM sleep, characterised by high levels of brain activity and vivid dreaming, earlier than men.
Variations in body clocks
The all-woman research ream from the University of Southampton in the UK, and Stanford University and Harvard University in the United States, found differences between the sexes are also present in our circadian rhythms.
They found melatonin, a hormone that helps with the timing of circadian rhythms and sleep, is secreted earlier in women than men. Core body temperature, which is at its highest before sleep and its lowest a few hours before waking, follows a similar pattern, reaching its peak earlier in women than in men.
Corresponding to these findings, other studies suggest women’s intrinsic circadian periods are shorter than men’s by around six minutes.
Dr Renske Lok from Stanford University, who led the review, says: “While this difference may be small, it is significant. The misalignment between the central body clock and the sleep/wake cycle is approximately five times larger in women than in men. Imagine if someone’s watch was consistently running six minutes faster or slower. Over the course of days, weeks, and months, this difference can lead to a noticeable misalignment between the internal clock and external cues, such as light and darkness.
“Disruptions in circadian rhythms have been linked to various health problems, including sleep disorders, mood disorders and impaired cognitive function. Even minor differences in circadian periods can have significant implications for overall health and well-being.”
Men tend to be later chronotypes, preferring to go to bed and wake up later than women. This may lead to social jet lag, where their circadian rhythm doesn’t align with social demands, like work. They also have less consistent rest-activity schedules than women on a day-to-day basis.
Impact on metabolism
The research team also investigated if the global increase in obesity might be partially related to people not getting enough sleep – with 30% of 30- to 64-year-olds sleeping less than six hours a night in the United States, with similar numbers in Europe.
There were big differences between how women’s and men’s brains responded to pictures of food after sleep deprivation. Brain networks associated with cognitive (decision making) and affective (emotional) processes were twice as active in women than in men. Another study found women had a 1.5 times higher activation in the limbic region (involved in emotion processing, memory formation, and behavioural regulation) in response to images of sweet food compared to men.
Despite this difference in brain activity, men tend to overeat more than women in response to sleep loss. Another study found more fragmented sleep, taking longer to get to sleep, and spending more time in bed trying to get to sleep were only associated with more hunger in men.
Both women and men nightshift workers are more likely to develop type 2 diabetes, but this risk is higher in men. Sixty-six per cent of women nightshift workers experienced emotional eating and another study suggests they are around 1.5 times more likely to be overweight or obese compared to women working day shifts.
The researchers also found emerging evidence on how women and men respond differently to treatments for sleep and circadian disorders. For example, weight loss was more successful in treating women with OSA than men, while women prescribed zolpidem may require a lower dosage than men to avoid lingering sleepiness the next morning.
Dr Chellappa added: “Most of sleep and circadian interventions are a newly emerging field with limited research on sex differences. As we understand more about how women and men sleep, differences in their circadian rhythms and how these affect their metabolism, we can move towards more precise and personalised healthcare which enhances the likelihood of positive outcomes.”
Researchers at Stockholm University have discovered that sleep affects how old you feel, with important health implications. The study is published in the scientific journal Proceedings of the Royal Society B.
Feeling young is not just a matter of perception: it is actually related to objective health outcomes. Previous studies have shown that feeling younger than one’s actual age is associated with longer, healthier lives. There is even support for subjective age to predict actual brain age, with those feeling younger having younger brains.
“Given that sleep is essential for brain function and overall well-being, we decided to test whether sleep holds any secrets to preserving a youthful sense of age,” says Leonie Balter, researcher at the Department of Psychology, Stockholm University.
In the first study, 429 individuals aged 18 to 70 were asked how old they felt, how many days in the past month they had not gotten enough sleep, and how sleepy they were.
It turned out that for each night with insufficient sleep in the past month, participants felt on average 0.23 years older.
In a second study, the researchers tested whether it was indeed the lack of sleep causing participants to feel older. They conducted an experimental sleep restriction study involving 186 participants aged 18 to 46. Participants restricted their sleep to four hours a night for two nights and another time slept sufficiently for two nights, with nine hours in bed each night.
After sleep restriction, participants felt on average 4.4 years older compared to when having enjoyed sufficient sleep.
The effects of sleep on subjective age appeared to be related to how sleepy they felt. Feeling extremely alert was related to feeling 4 years younger than one’s actual age, while extreme sleepiness was related to feeling 6 years older than one’s actual age.
“This means that going from feeling alert to sleepy added a striking 10 years to how old one felt,” says Leonie Balter, and states that the implications for our daily lives are clear:
“Safeguarding our sleep is crucial for maintaining a youthful feeling. This, in turn, may promote a more active lifestyle and encourage behaviours that promote health, as both feeling young and alert are important for our motivation to be active.”
Sleeping fewer than seven hours is associated with a higher risk of developing hypertension over time, according to a study presented at the American College of Cardiology’s Annual Scientific Session.
While the association between sleep patterns and hypertension has been reported, evidence about the nature of this relationship has been inconsistent, according to researchers. The current analysis pools data from 16 studies conducted between January 2000 and May 2023, evaluating hypertension incidence in 1 044 035 people from six countries without a prior history of hypertension over a median follow-up of five years (follow-up ranged from 2.4 to 18 years). Short sleep duration was significantly associated with a higher risk of developing hypertension after adjusting for demographic and cardiovascular risk factors, including age, sex, education, BMI, blood pressure, smoking status etc. Furthermore, the association was found to be even stronger for those getting less than five hours of sleep.
“Based on the most updated data, the less you sleep – that is less than seven hours a day – the more likely you will develop high blood pressure in the future,” said Kaveh Hosseini, MD, assistant professor of cardiology at the Tehran Heart Center in Iran and principal investigator of the study. “We saw a trend between longer sleep durations and a greater occurrence of high blood pressure, but it was not statistically significant. Getting seven to eight hours of sleep, as is recommended by sleep experts, may be the best for your heart too.”
The study found that sleeping less than seven hours was associated with a 7% increased risk of developing hypertension, which spiked to 11% when reported sleep duration was less than five hours. By comparison, diabetes and smoking are known to heighten one’s risk of hypertension by at least 20%, Hosseini said.
While the study did not look at why this might be the case, Hosseini said that disrupted sleep could be to blame. For example, he said lifestyle habits or comorbid conditions such as overeating, alcohol use, nightshift work, certain medication use, anxiety, depression, sleep apnoea or other sleep disorders may be factors.
Researchers were surprised there were no age-based differences in the association between sleep duration and hypertension given that sleep patterns tend to shift with age. Participants ranged in age from 35.4 years to 60.9 years and 61% were female. When compared with men, females who reported less than seven hours of sleep had a 7% greater risk of developing hypertension.
“Getting too little sleep appears to be riskier in females,” Hosseini said. “The difference is statistically significant, though we are not sure it’s clinically significant and should be further studied. What we do see is that lack of good sleep patterns may increase the risk of high blood pressure, which we know can set the stage for heart disease and stroke.”
It’s important for people to talk with their health care team about their sleep patterns, especially if they have disrupted sleep that might be due to obstructive sleep apnoea. Sleep apnoea has been tied to higher rates of high blood pressure, stroke and coronary artery disease.
This study has several limitations, including that sleep duration was based on self-reported questionnaires, so changes in sleep duration over the follow-up period were not assessed. Moreover, there were variations in how short sleep duration was defined between the studies (fewer than five or six hours).
“Further research is required to evaluate the association between sleep duration and high blood pressure using more accurate methods like polysomnography, a method for evaluating sleep quality more precisely,” Hosseini said. “Moreover, the variations in reference sleep duration underline the need for standardised definition in sleep research to enhance the comparability and generalisability of findings across diverse studies.”
There were multiple unsafe sleep practices at play in more than three-quarters of Sudden Unexpected Infant Deaths reported in 23 U.S. jurisdictions between 2011 and 2020, according to a new study published in Pediatrics. The researchers say the findings underscore the need for more comprehensive safe-sleep education for new parents, including from healthcare providers.
Of 7595 infant deaths reviewed, almost 60% of the infants were sharing a sleep surface, such as a bed, when they died.
This practice is strongly discouraged by sleep experts, who warn that a parent or other bed partner could unintentionally roll over and suffocate the baby.
Infants who died while sharing a sleep surface were typically younger (less than 3 months old), non-Hispanic Black, publicly insured, and either in the care of a parent at the time of death or being supervised by someone impaired by drugs or alcohol.
These infants were typically found in an adult bed, chair or couch instead of the crib or bassinet recommended by sleep experts.
“The large number of hazardous sleep practices for both infants who were sharing a sleep surface and sleeping alone at the time of death is alarming,” said researcher Fern Hauck, MD, MS, a safe-sleep expert at UVA Health and the University of Virginia School of Medicine.
“These are known risk factors for SUID [Sudden Unexpected Infant Death], and tells us that we need to do a better job of working with families to increase acceptance of the recommendations to create safer sleep spaces for their infants.”
Sudden Unexpected Infant Deaths
To better understand the factors contributing to SUID and improve safe-sleep messaging, Hauck and her collaborators analysed data from the federal Centers for Disease Control and Prevention’s SUID Case Registry.
The researchers obtained important insights on the prevalence of practices such as prenatal smoking, a known risk factor for SUID, and breastfeeding, which is thought to have a protective benefit.
More than 36% of mothers of infants who died had smoked while pregnant. This percentage was higher among moms who bed shared than those who didn’t, 41.4% to 30.5%. Both bed sharers and non-bed sharers had breastfed at similar rates.
The researchers note that it was rare for bedsharing to be the only risk factor present during a child’s death.
The findings highlight the need for better public education about safe-sleep practices, and for care providers to take a more active role in teaching new parents about the practices, the researchers say.
“Our findings support comprehensive safe sleep counselling for every family at every encounter beyond just asking where an infant is sleeping,” the researchers wrote
In addition to helping parents understand safe-sleep practices, care providers should take steps to ensure parents can follow those practices once they leave the hospital.
For example, some families may not have the means to purchase a crib or bassinet; a hospital might direct them to resources to help with that.
“SUID deaths in the U.S. are still higher than in most other countries, and this is unacceptable,” Hauck said.
“Clinicians and others caring for infants need to have thoughtful conversations with families at risk to understand the barriers to following safe-sleep guidelines and find ways to work together to overcome them.”
Research into the link between disordered sleep and disease show an outsized burden on the most vulnerable. It’s sounding alarms for sleep equity to have a place on the public health agenda, reports Ufrieda Ho.
Scientists are increasingly connecting the dots on how a lack of sleep places a disproportionate health burden on at-risk population groups, including people living with HIV, women, informal workers, the elderly and the poor.
This year’s World Sleep Day on 15 March focuses on sleep equity. Researchers say that tackling sleep inequity and raising awareness for the importance of sleep as a pillar of good health could help stave off several looming public health pressures.
The lack of healthy sleep is linked to cardiovascular disease, obesity, hypertension, diabetes, mental health conditions and dementia. In South Africa, understanding the connection between sleep and HIV is also key to managing the health of the large ageing population of people living with the disease.
Karine Scheuermaier is associate professor at the Wits University Brain Function Research Group. The country’s oldest sleep laboratory founded in 1982 is based at the university’s medical school in Parktown, Johannesburg.
“Society understands the role of exercise and diet in good health but somehow sleep has not had the same kind of awareness or priority, even if sleep is linked to how well your body functions and your chances of developing disease,” she says. “We do everything else at the expense of sleep. Sleep is somehow a symbol of laziness in a work-driven society and we need to change this thinking.”
Sleep inequity in SA
Sleep inequity is linked to socio-economic realities, she says. Sleep inequity might affect the person who lives in an environment where safety and security is neglected or where there is a high threat of gender-based violence. It could also be having to navigate apartheid city planning that forced black people to live far from job hubs. This legacy means today many workers still wake up early to face long work commutes daily. There could also be inequity in division of labour in households, when one person wakes up to take care of children or elderly family members in the home.
Living in overcrowded informal settlements also presents disturbances for good sleep, including high levels of noise and bright floodlights as street lighting. Those who work in unregulated or informal sectors, including shift work or digital platform workers, like e-hailing drivers, are prone to lose out on quality sleep.
clinic that does clinical work, research, and training. Chandiwana says homing in on the intersection of HIV and sleep is critical in a South African context.
“The average person living with HIV who has started antiretroviral treatment on time should live as long as a person who doesn’t have HIV. But what we know is that the person with HIV is on average, living 16 years less of good health. They are more likely to develop type II diabetes, mental health issues, obesity, and heart disease – and we know poor sleep is linked to this,” she says.
Chandiwana says sleep science is still a relatively new field of medicine and the nascent research is still looking to better understand how sleep deprivation triggers immune pathways and chronic inflammation in people living with HIV, even those who are healthy and respond positively on treatment.
A current study at the clinic is looking into the intersection of obesity, sleep apnoea, and women living with HIV. Chandiwana says because so much is unknown, the issue of sleep equity extends to support and funding for more locally appropriate sleep research. Medical school curricula needs to change and more avenues to train people in sleep research needs to be established, she says.
“We have very little African data on sleep disorders and disordered sleep,” she says. She argues we need better data on things like how many people are affected by poor sleep, a better understanding of what is causing it and what it means, and then we need to present these findings to public health authorities to look at it as a public health issue.
“We do have specific challenges in our country. If you are trying to explain to someone, who isn’t South African, how the impact of load-shedding affects sleep or how living in a shack affects sleep, it’s not always easy to do,” she says.
Chandiwana says countries in the global North are already counting insufficient quality sleep as an economic cost measured in loss of productivity, efficiency, safety and society’s well-being. They are also changing public health policies accordingly. South Africa and the rest of the continent stand to be left behind, she says.
How to get better sleep in SA
Chandiwana says: “There is no lab in South Africa that does sleep studies for people in the public sector and no place in the public sector for people to even be diagnosed for a sleep disorder – so services are extremely limited. With something like sleep apnoea, we can’t offer patients in the public sector the gold standard intervention of CPAP [continuous positive airway pressure, which is a device of a face mask, a nose piece, and a hose that delivers a steady flow of air pressure to keep airways open while someone sleeps] because this is financially out of reach. Instead, we have to work with patients to help them lose weight and do positional therapy like training them to sleep on their backs.”
Other ways to get better sleep without costly intervention or sleeping tablets, the two scientists say, include getting exercise, not having food, stimulants or alcohol two to three hours before bedtime, limiting screen time of all kinds in the hour around bedtime, getting exposure to the early morning sunlight each day, keeping sleeping areas dark, quiet and at a comfortable temperature, and developing fixed sleep routines and sleep time rituals – like brushing your teeth, putting on pyjamas, reading for a short period and then going to sleep.
Ultimately, Chandiwana suggests it all comes back to building awareness that healthy sleep is part of health rights.
“We have to fight for sleep equity and we need people to know that sleep is not elitist – it’s not just reserved for some,” she says, “and we should not be accepting poor sleep as the norm”.
The rhythmic waves of electric pulses produced by neurons during sleep have long fascinated science and defied explanation. Slow brain waves are associated with restful, refreshing sleep. Now, scientists have found that brain waves help flush waste out of the brain during sleep. Individual nerve cells coordinate to produce rhythmic waves that propel fluid through dense brain tissue, washing the tissue in the process. This finding could help lead to new ways to treat diseases such as Alzheimer’s.
“These neurons are miniature pumps. Synchronised neural activity powers fluid flow and removal of debris from the brain,” explained first author Li-Feng Jiang-Xie, PhD, a postdoctoral research associate in the Department of Pathology & Immunology. “If we can build on this process, there is the possibility of delaying or even preventing neurological diseases, including Alzheimer’s and Parkinson’s disease, in which excess waste – such as metabolic waste and junk proteins – accumulate in the brain and lead to neurodegeneration.”
The Washington University School of Medicine in St. Louis researchers published their findings in Nature.
In carrying out the energy-demanding tasks of the brain’s functions, brain cells consume nutrients and create metabolic waste, which must be disposed of.
“It is critical that the brain disposes of metabolic waste that can build up and contribute to neurodegenerative diseases,” said Jonathan Kipnis, PhD, the Alan A. and Edith L. Wolff Distinguished Professor of Pathology & Immunology and a BJC Investigator. Kipnis is the senior author on the paper. “We knew that sleep is a time when the brain initiates a cleaning process to flush out waste and toxins it accumulates during wakefulness. But we didn’t know how that happens. These findings might be able to point us toward strategies and potential therapies to speed up the removal of damaging waste and to remove it before it can lead to dire consequences.”
But the dense brain makes cleaning difficult. Cerebrospinal fluid surrounding the brain enters and weaves through intricate cellular webs, collecting toxic waste as it travels. Upon exiting the brain, contaminated fluid must pass through a barrier before spilling into the lymphatic vessels in the dura mater, which envelopes the brain. But what powers the movement of fluid into, through and out of the brain?
Studying the brains of sleeping mice, the researchers found that neurons drive cleaning efforts by firing electrical signals in a coordinated fashion to generate rhythmic waves in the brain, Jiang-Xie explained. They determined that such waves propel the fluid movement.
The research team silenced specific brain regions so that neurons in those regions didn’t create rhythmic waves. Without these waves, fresh cerebrospinal fluid could not flow through the silenced brain regions and trapped waste couldn’t leave the brain tissue.
“One of the reasons that we sleep is to cleanse the brain,” Kipnis said. “And if we can enhance this cleansing process, perhaps it’s possible to sleep less and remain healthy. Not everyone has the benefit of eight hours of sleep each night, and loss of sleep has an impact on health. Other studies have shown that mice that are genetically wired to sleep less have healthy brains. Could it be because they clean waste from their brains more efficiently? Could we help people living with insomnia by enhancing their brain’s cleaning abilities so they can get by on less sleep?”
Brain wave patterns change throughout sleep cycles. Of note, taller brain waves with larger amplitude move fluid with more force. The researchers are now interested in understanding why neurons fire waves with varying rhythmicity during sleep and which regions of the brain are most vulnerable to waste accumulation.
“We think the brain-cleaning process is similar to washing dishes,” neurobiologist Jiang-Xie explained. “You start, for example, with a large, slow, rhythmic wiping motion to clean soluble wastes splattered across the plate. Then you decrease the range of the motion and increase the speed of these movements to remove particularly sticky food waste on the plate. Despite the varying amplitude and rhythm of your hand movements, the overarching objective remains consistent: to remove different types of waste from dishes. Maybe the brain adjusts its cleaning method depending on the type and amount of waste.”
A discovery by researchers in Switzerland reveals that the sleeping body also reacts to the external world during sleep, explaining how some information from the sensory environment can affect sleep quality.
A collaboration between University of Liège and University of Fribourg has investigated whether the body is truly disconnected from the external world during sleep.
To do so, they focused on how heartbeat changes when we hear different words during sleep.
They found that relaxing words slowed down cardiac activity as a reflection of deeper sleep and in comparison to neutral words that did not have such a slowing effect.
This discovery, published in the Journal of Sleep Research, sheds new light on brain-heart interactions during sleep.
Matthieu Koroma (postdoctoral researcher), Christina Schmidt and Athena Demertzi (rsesearch) from the GIGA Cyclotron Research Center at ULiège teamed up with colleagues from University of Fribourg led a previous study analysing brain data (electroencephalogram) showing that relaxing words increased deep sleep duration and sleep quality, showing that we can positively influence sleep using meaningful words.
By that time, the authors hypothesised that the brain also remains able to interpret sensory information in a way that makes our body more relaxed after hearing relaxing words during sleep.
In this new study, the authors had the opportunity to analyse cardiac activity to test this hypothesis and found that the heart slows down its activity only after the presentation of relaxing, but not control words.
Markers of both cardiac and brain activity were then compared to disentangle how much they contributed to the modulation of sleep by auditory information.
Cardiac activity has been indeed proposed to directly contribute to the way we perceive the world, but such evidence was so far obtained in wakefulness.
With these results, the ULiège researchers showed that it was also true in sleep, offering a new perspective on the essential role of bodily reactions beyond brain data for our understanding of sleep.
“Most of sleep research focuses on the brain and rarely investigates bodily activity,” says Dr Schmidt.
“We nevertheless hypothesise that the brain and the body are connected even when we cannot fully communicate, including sleep. Both brain and body information need then to be taken into account for a full understanding of how we think and react to our environment,” explains Dr Demertzi.
“We shared freely our methodology following the principles of Open Science hoping that the tools that helped to make this discovery will inspire other researchers to study the role played by the heart in other sleep functions,” Dr Koroma advocates.
This work offers a more comprehensive approach about the modulation of sleep functions by sensory information. By looking into the cardiac responses to sounds, we may, for example, study in the future the role of the body in the way sounds influence emotional processing of memories during sleep.
With frequent and long stints at their computers, the average gamer is a sedentary night owl, often compromising on sleep – especially quality sleep – and being exposed to too much blue light. The topic has been explored in University of Cape Town (UCT) PhD candidate Chadley Kemp’s doctoral thesis, a meaty study of over 70 000 words.
Kemp’s research into habitual gaming activities is supervised by Associate Professor Dale Rae, a sleep researcher and senior lecturer at the Health Through Physical Activity, Lifestyle and Sport Research Centre (HPALS) in the Faculty of Health Sciences.
This work is founded on Kemp’s 2018 research underpinning a master’s in medical science at UCT’s former Department of Exercise Science and Sports Medicine in the Sports Science Institute of South Africa. This was upgraded to a PhD in 2020.
His research (he is an esports and video game enthusiast) explores adult esports players’ sleep, health status, light exposure patterns and physical activity.
“We know that sleep affects mental functioning in general, but we weren’t sure about the extent to which this applied to esports players,” said Kemp.
Framework for healthier gameplay
Kemp’s goal is to produce objective data that will guide the development of a framework aimed at promoting healthier gameplay standards and encouraging policy reform within the esports industry.
The tests they used to assess neurocognitive performance were intended to serve as proxies for certain aspects of esports performance because they tested specific mental skills important to gaming, he added.
“We gathered it would be a useful addition to compel gamers to adopt better sleep and lifestyle behaviour changes if it meant … that their health would improve, and they would benefit from better in-game performance – and get an edge over their competitors!”
Kemp’s focus is not on professional gamers, but what he calls “the missing middle” of the esports community: the amateur and semi-competitive gamers.
“This group doesn’t have the same infrastructure and support as their professional counterparts,” he explained. “But what makes them particularly interesting is the fact that they have to balance their gaming commitments with holding down a job, studies, or juggling family or household commitments.”
Global attraction
Esports are burgeoning across the globe – and not only among competitive gamers but audiences too. Writing in the South African Journal of Sports Medicine, Kemp and his co-authors noted that globally competitive gaming attracts 532 million fans alone, according to statistics released in 2022.
However, his study wasn’t motivated by an influx of gamers presenting themselves with sleep difficulties at Associate Professor Rae’s sleep consultancy, Sleep Science. Rather, it stemmed from a broader observation and concern within the local esports community about gamers and poor-quality and short-duration sleep, high levels of sedentarism, and excessive exposure to artificial or electronic night at night.
Based on these conversations and endorsed by anecdotal evidence from within the esports industry, Kemp said he and Rae were able to determine that sleep curtailment had seemingly become a “rite of passage” among gamers. Primarily, most gaming takes place at night because of gamers’ daytime commitments.
As there wasn’t much literature on the topic (much of it is focused on the implications of gaming in children and adolescents) and most studies were survey-based and didn’t target esports players or those regularly engaged with gaming, there was significant knowledge gap that needed filling. As a demographic, Kemp is particularly interested in adult esports players because of the greater health risks posed by age and unhealthy lifestyle factors, such as smoking and alcohol consumption.
Because he needed a tool to measure sleep and physical activity concurrently, he validated the Actiwatch, a special research device, to do this. The device also measures light exposure. For his sample group, Kemp recruited eligible esports players and measured variables of interest. These were clinical measures (anthropometry, blood pressure, blood markers) and self-report data (questionnaires on sleep, chronotype, daytime sleepiness and gaming addiction) and their cognitive performance.
“We also included non-gamers in our study, so we could compare our gamers against people who were not gamers. In total, we had 59 male participants (31 gamers; 28 non-gamers). (The females volunteering to participate did not meet the study’s inclusion criteria.) For a week, these individuals wore the Actiwatch to track their sleep, physical activity, and light exposure.”
Key findings
The key findings of his research make for interesting reading:
esports players have comparable sleep duration to non-gamers (control group) but tend to sleep later than others. They hit the middle of their sleep cycle around 04:08 compared to 03:01 for the control group.
A much larger percentage of esports players (45.2%) showed night-oriented habits (or evening chronotypes), ie they are more active and alert at night. This is in contrast to only 7.1% of the control group showing similar evening tendencies.
They nap more during the day, but their night sleep duration is similar to that of the control groups.
There was no significant difference in risks related to heart diseases or metabolic diseases between the two groups, which Kemp speculates might be related to their young age. But most of the health markers were tentatively raised, which could point to worse cardiometabolic health in future.
Esports players smoke more.
Esports players performed better in brain-based tasks, showing better attention and accuracy, and making fewer mistakes.
Esports players are less active than the control group. They sit more (11.2 vs 9.1 hours a day) and are less physically active, whether it’s moderate- or vigorous-intensity activity.
Esports players have specific active and inactive hours. They are less active in the early morning and certain evening hours but are more active around midnight.
Esports players are exposed to dimmer light for a more significant part of their day, and their exposure to bright light happens later at night.
This work is important for several reasons, said Kemp. A key takeaway from the research revolves around chronotypes.
“Esports players seem to have sleep patterns that align with being night owls and this may be influenced both by their natural tendencies and their gaming habits. It’s also possible that a genetic disposition and exposure to artificial light from screens collectively contributes to these sleep patterns.
“The combined effect is thought to create a cycle where their preference for evening activities leads to more gaming, which in turn reinforces the night owl tendencies. This impacts on their sleep quality and quantity.”
He added: “Perhaps more obviously, gaming is a massively popular phenomenon that transcends age, sex, and geography. It’s a dominant form of entertainment and its competitive arm, esports, is progressing towards acceptance as a genuine form of sporting competition.”
From the neurocognitive side, it’s clear that gaming can sharpen several cognitive abilities, such as attention and problem-solving.
“However, the catch is, if you’re not getting enough sleep, these enhanced skills could take a hit,” said Kemp. “Gamers might see slower reactions, flawed decision-making, and even a drop in their in-game stamina. So, while gaming certainly has its merits and can even boost certain mental skills, it doesn’t come without health considerations. “
Kemp’s research is aimed at ensuring that anyone engaged with gaming or esports does so in a healthy way.
“The purpose is to create a steppingstone towards health regulation in gaming and esports,” he said. “By creating awareness and providing evidence-based recommendations to prevent chronic health problems caused by unhealthy gaming behaviour, it supports individual decision making, governments, and policy makers. It’s valuable to anyone involved in or impacted by gaming.”
Kemp’s guidelines for gamers:
Get between seven and nine hours’ sleep a night and keep a regular sleep schedule (on weekends too).
Set fixed waking and sleep times to establish a more robust sleep–wake cycle.
For better sleep, ensure your bedroom is dark, quiet, and cool (16-18°C is optimal).
Limit the amount of light exposure in the hours before bedtime (including light from phones, laptops, TVs, etc).
Limit caffeine to the morning and afternoon. This means no energy drinks during those night-time gaming sessions).
