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Can’t sleep? Your phone may not be to blame

UTM study finds that restless sleep habits may be associated with our early hunter-gatherer lifestyles

Can’t sleep? Your phone may not be to blame

Restless sleep is commonly attributed to modern-day sedentary lifestyles, mobile phones, and electric lighting, however, according to a study conducted by Assistant Professor of Anthropology at UTM David Samson, it may actually be linked to ancient survival methods used by humans for nocturnal threat protection.

Samson conducted a study that showed how anxious sleeping habits in humans may be linked to the sentinel hypothesis. This hypothesis, originally proposed by Frederick Snyder in 1966, postulates that group-living species use a defence mechanism involving a few individuals staying awake and alert during the night while the majority of the group is asleep and vulnerable.

Samson and the study’s co-authors claim that sleeping in mixed-age groups has evolutionary benefits, as the different sleeping schedules of older and younger individuals allows for a few members of the group to be awake and vigilant while the others rest. Charlie Nunn, a co-author and Professor of Evolutionary Anthropology at Duke University, links these lighter sleep patterns to the ability to better defend oneself in the presence of a threat.

The study examined the Hadza tribe of northern Tanzania because of its active hunting and gathering lifestyle, similar to early human survival methods. The Hadza tribe uses no electronics or climate control, and both male and female individuals sleep together in a mixed-age group in the outdoors. They live under constant exposure to meteorological pressures, other people, and animals, and they must adapt to these challenges on a day-to-day basis, similar to early humans.

Thirty-three healthy Hadza men and women were studied for a period of 20 days, during which their sleeping patterns were tracked with watch-like accessories that monitored their movements. They woke up often to smoke, relieve themselves, and watch over their children.

On average, the men and women slept for 6.5 hours each night. However, the older tribe members tended to sleep earlier in the night, whereas the younger members slept later. During the study, the participants were all simultaneously asleep for just 18 minutes.

“The discovery that Hadza hunter-gatherers have little to no synchronous sleep (at any given nighttime minute, 40% of the adults are awake) was very surprising and also strong support for the sentinel hypothesis in humans,” Samson wrote in an email to The Varsity.

Although the Hadza tribe leads a drastically different lifestyle from people living and sleeping in non-hunting and gathering environments, their sleeping habits mimic those of early human ancestors who defended against nocturnal predators and showcases our evolutionary history. These findings suggest that the unsteady sleeping patterns we face may not solely be attributed to cell phone or electronics usage, but may in fact correlate with our ancestry.

“In the West we have a tendency to label phenomenon that fall outside the statistical bell curve as non-normative,” Samson explained. “In fact, it may be that such variation was adaptive in our ancestral past, and we have an occurrence of ‘evolutionary mismatch’ — where our ancient hardware conflicts with our modern social and technological context.”

Samson hopes that these findings will normalize sleep flexibility and variability throughout an individual’s life, as well as reduce sleep anxiety and improve sleep quality. “My lab’s research will focus on measuring sleep-wake patterns in traditional people worldwide to generate a global sleep database,” Samson said. “Moreover, we will continue to measure sleep architecture all across the primate order to understand how non-human and human sleep differ from each other and other mammals.”

Correction: A previous version of this article incorrectly stated that the Hadza men and women slept for nine hours each night. They slept for 6.5. 

Science in brief

A round-up of the top science stories from around the university

Science in brief

Dangerous driving

What may seem obvious to any good driver can now be backed up by statistics: dangerous drivers are more likely to hit children on their way to school.

Researchers from York University, the University of Toronto, and The Hospital for Sick Children camped out in front of schools during their morning drop-off hours, measuring pedestrian traffic and scanning the road for hazardous driving habits. Their observations were compared with 12 years of police data on pedestrian-motor vehicle collisions (PMVCs) near Toronto elementary schools. The study revealed that collisions involving children happen more often near schools with dangerous driving trends.

The most common offense? Of the 118 schools studied, 88 per cent displayed instances of unsafe parking and improper drop-offs, such as children being released from the wrong side of the street. Trends were higher in schools near high-speed roadways. Researchers urge the city to employ new strategies to alleviate traffic around school zones.

— Alastair McNamara


Study shows depression affects alertness more than lack of sleep

A new study lead by Azmeh Shahid of the Sleep Research Laboratory in U of T’s Department of Psychiatry is the first of its kind to connect depressive symptoms with impaired alertness.   

The researchers used the Toronto Hospital Alertness Tests (THAT), a scale asssessing alertness, to evaluate 60 healthy adults against 264 diagnosed patients. The participants’ average score (on a scale of zero to 50) was around 35 for the control group. A score below 20.5 is the cut-off point for THAT and it indicates “clinically significant” decreases in levels of alterness.   

This cut-off was used to define the patients as either having “normal” or “impaired” alertness. The results showed that daytime sleepiness is not the same as poor alertness, and that depressive symptoms like fatigue had a stronger effect on alertness levels than tiredness. 

Dr. Shahid said the results of the study “did not surprise” the research team, as other clinical patients have been observed to experience daytime sleepiness and alertness at the same time. 

Dr. Shahid explained the results of the study are “very exciting” because THAT can be used to differentiate alertness from sleepiness, which can aid in future studies. The first quantitative definition of “normal levels of alertness” was proposed by the study, but more research is still needed to solidify this definition. 

“I think this will have huge impact in clinical practice,” Dr. Shahid added.

— Sophia Savva 

Don’t Worry, Be Happy

With the loonie sinking and the world economy sputtering, it is hard not to worry about world issues. A new study warns against worrying too much, lest our brains turn to mush. 

Dr. Linda Mah of the University of Toronto and her colleagues examined recent studies of stress and anxiety in animal models and healthy individuals. Surprisingly, they found that chronic stress and anxiety can cause long-lasting damage in the brain.

Stress is a normal part of life, but if anxiety becomes chronic, it can lead to the degeneration and impairment of the brain’s hippocampus and prefrontal cortex. The former is known to play an important role in memory and the regulation of emotions, while the latter has been associated with personality distinction.   

The stress-induced damage to these parts of the brain leads to increased risk for depression and even dementia. 

The study concludes on a hopeful note by suggesting that stress-induced damage is “not completely irreversible.” Antidepressant treatment and physical activity may reverse brain damage, as these treatments have been found to increase the rate of hippocampal recovery. Either way, don’t worry about your worrying.

— Hariyanto Darmawan

Science in brief

A round-up of the top science stories from around the university

Science in brief

Are smart people less racist?

This year’s lily-white Oscar nominations list has once again sparked a new debate on racism in Hollywood. A new study from the University of Toronto is adding to this already searing-hot debate by indicating that, while the smarter population of white people are less likely to be prejudiced against black people, they are no more likely to support policies that remediate racial inequality.

Researcher Geoffrey Wodtke analyzed the data from a survey of over 44,000 white respondents, conducted over the period between 1972 and 2010. The survey showed that white people with higher verbal ability are less likely to hold anti-black prejudice and more likely to support racial integration in principle. For example, 46 per cent of respondents who scored the lowest on the verbal ability test think that “blacks are lazy”, while only 29 per cent of those who scored the highest agreed with that. 

There is, a catch however; the same white people who had been deemed smarter were found to be no more likely to support remedial policies, such as government aid for black people, tax incentives for businesses to move to largely black areas, and increased funding for predominantly black schools. They are even less likely to support preferential hiring policies.

So, are the smart ladies and gentlemen who voted in the white-only Oscar nominees racist? This study suggests that there is no simple answer to this question.

— Hariyanto Darmawan

For seniors, poor sleep may increase stroke risk, study says

If you are not yet convinced that lack of sleep and physical health are intimately intertwined, yet another study has come forward, this time showing a new link between stroke risk and a poor night of rest.

The study, which has contributions from the University of Toronto, showed how sleep fragmentation — waking repeatedly during sleep — is associated with brain blood vessel damage and increased stroke risk.

The study assessed sleep fragmentation and brain blood vessel damage in 315 autopsied individuals. On average, participants experienced seven disruptions per hour of sleep.

The team, which was led by Dr. Andrew Lim, an assistant professor of neurology at U of T, found that sleep fragmentation was associated with arteriole (small arterial blood vessels) wall thickening and tissue death. This effect was due to inadequate blood flow in an area of the brain called the subcortex.

Lim and his fellow researchers noted that such associations remained statistically significant even after controlling for factors such as total daily rest and activity, cardiovascular disease, Alzheimer’s disease, pain and depression.

Lim explained in a press release that the types of damage observed can result in chronic progressive cognitive and motor deterioration in addition to increased stroke risk.

Lim however cautioned against inferring a causal relationship between sleep fragmentation and blood vessel damage. According to Lim, it is possible that the blood vessel damage caused the sleep disruptions, or that there was an underlying mechanism that was the cause of both issues.

— Hannah Fung

Did Your Child Learn to Lie Early? This May be Why

In our society, the ability to lie can be harmless and sometimes – as in the case of white lies – necessary for social interactions in adulthood. Typically, lying emerges in children aged two-to-three years old, and develops rapidly from the third to the seventh year. But how is it that lies come about, and why are some children more likely to verbally deceive than others?

A team of researchers, including Xiao Pan Ding and Dr. Kang Lee from U of T’s Dr. Eric Jackman Institute of Child Study, are among the first to link lying in children to their understanding of individual mental states. 

According to their recently published study, the more a child grasps that their own beliefs, desires, intents and perspectives differ from others, the more they will lie.

In the study, three-year-old children who were initially incapable of lying were split into two groups, where half had mental state training in the form of story-telling, verbal exercises, games and executive-functioning tasks, and half had non-mental state training involving more quantitative tasks. After twelve days of training, follow-up tests determined that the mental-state training group had a significantly higher likelihood of lying than the control group. The effects of lying persisted for a month after the practise.

  Laura Nguyen

Cheap jewelry; high cost

While you think you’re paying a low price for the latest trendy jewelry at Aldo and Ardene, you may actually be gambling with your health.

In a recent investigation by CBC Marketplace involving researchers from the University of Toronto and École Polytechnique de Montréal, 50 pieces of costume jewelry from different stores were tested for cadmium, a carcinogenic heavy metal. Seven pieces from Aldo and Ardene were found to contain between 15 and 7000 times more cadmium than deemed child-safe by Health Canada. A pendant hanging from one Ardene necklace was comprised of almost pure cadmium — the highest quantity Canada has documented for an object like this.

The risk does not lie in wearing the jewelry, but in chewing or ingesting it. If chronically exposed to this toxic metal over a period of time, issues such as kidney failure and bone loss could arise. Cadmium can also damage the central nervous system, affect blood pressure, and cause other complications. Cadmium exposure is particularly dangerous for children, as their bodies absorb cadmium more easily. An Aldo bracelet charm, which contained 79 per cent cadmium, would be enough to release dangerous amounts of it into the body of a small child if consumed. According to Health Canada, there have so far not been any reported cases of sickness from ingesting cadmium jewelry.

Regardless, Aldo has still stated that it would remove the toxic jewelry from stores, while Ardene said it would look further into the matter.

— Sophia Savva