Leela McKinnon on the impact of major lifestyle changes on sleep patterns and circadian rhythms in Indigenous populations in Guatemala and Mexico
Recent studies by evolutionary sleep anthropologists demonstrate the influence of environmental, social, and technological factors on human sleep patterns.
Leela McKinnon, a PhD student in Evolutionary Anthropology at the University of Toronto Mississauga (UTM), studies the evolution of human sleep. Specifically, she explores how a complex interaction of ecological and sociological drivers such as environment, culture, and technology shape human sleep patterns. Her current research focuses on sleep patterns and circadian rhythm analysis of Indigenous populations in a small-scale Maya community in Guatemala and the Wixárika community living in the mountains of Jalisco and Nayarit, Mexico.
After earning her undergraduate degree in Anthropology at Penn State University, she worked in healthcare in an ophthalmology office. McKinnon gained firsthand experience and observed the effects that lifestyle choices have on long-term outcomes. She only found interest in studying sleep once she met her current supervisor, David R. Samson, Director of UTM’s Sleep and Human Evolution Lab. Samson’s research documents sleep patterns in hunter-gatherers—individuals that rely on hunting, fishing, and foraging for food—and in small-scale agricultural communities in Guatemala, where he helped McKinnon build her connections for this project. McKinnon shares that she “loved looking anthropologically at something universal. Everyone sleeps, but not everyone sleeps the same way. So, what about sleep is similar or different across certain groups, and why? Where does health factor into this?”
Rapid urbanization has led industrialized societies into a sleep-loss epidemic. However, the comfort of our noise-buffered and temperature-controlled homes allows for longer and more efficient sleep. On the other hand, our circadian rhythms are far off due to varying sleep and wake times compared to small-scale groups such as the Kaqchikel in Guatemala.
Most sleep studies only look at one end of the extreme: either small-scale and completely non-industrial communities, or highly technological and completely industrialized populations. McKinnon’s and Samson’s co-authored paper “Technological infrastructure, sleep, and rest-activity patterns in a Kaqchikel Maya community” describes the Mayan community as “in-between” because it has undergone a transition to industrialization over the last few decades.
The study tested for sleep duration, sleep efficiency, rest-activity, wake/sleep times, and circadian rhythms among Maya participants. The results were compared to previously collected quantitative data from Hadza hunter-gatherers, small-scale agriculturalists in Malagasy (no industrialization), and the United States (full industrialization). They used actitraphs, a device worn on the wrist and used to measure activity when asleep and awake, because they are less invasive than alternative methods. The actigraphs have “an internal censor that’s measuring movement. When we do sleep studies, we measure in one-minute intervals, so it’s a lot of data points,” McKinnon shares. “It’s very comfortable, participants forget they are wearing them. They are waterproof so that people can wear them all the time.”
Moreover, sex, gender, age, labour demands, and social activities also affect sleep patterns. In the Maya community, men are leaving agricultural work for jobs in construction, working for chalet owners as a result of global market influence. Women work as cleaners, babysitters, hotel workers, and crafters. These changes in labour roles affect the sleep of both men and women in the community. Men exhibit later sleep times as they spend all day working and are more eager to socialize at night. Meanwhile, women have to wake up earlier to make breakfast.
In addition, homes in the Mayan community are made of adobe and concrete blocks which protect them against temperature fluctuations. Although it’s not as protected from the elements as homes in the urban US, it is more protected from environmental sleep disruptions than the Hadza hunter-gatherers are exposed to.
McKinnon and Samson’s results demonstrate that “the relationship between industrialization and sleep is not linear and is shaped by a complex interaction of environmental and social factors.” For example, some nights, rain contributed to shorter sleep duration, possibly because the roof, being made of tin, causes more noise during the night.
The results of the Mayan sample indicate their sleep was longer and more efficient than sleep in Hadza hunter-gatherers, but shorter and less efficient than more industrialized populations like the US. The study concluded, “the climate control and safety of urban settings may contribute to longer, better quality sleep while paradoxically also be leading to circadian rhythm weakening and desynchronization.”
The Mexico site is a much newer project, still in its early stages. McKinnon calls Wixárika “the most remote place I have ever been.” Due to more economic opportunities, many people within the community are moving to cities. “Indigenous ways of life are changing quite drastically and quickly all over the world, especially in these parts. Globally there is a lot more urbanization, and so groups that fairly recently relied on certain types of work and subsistence patterns are having to move to bigger cities or adopt different lifestyle patterns just with the growing urbanization,” says McKinnon. These are significant changes, and McKinnon is interested in finding out how these lifestyle changes will affect their sleep patterns.
McKinnon did a pilot study this past summer over six weeks; she measured the sleep of 20 people through surveys and interviews. She shares, “we found that average sleep duration was about 6.5 hours, similar to the published Maya and Malagasy results.” McKinnon feels that, historically, these remote Indigenous communities have been underrepresented in sleep research. “A lot of what we know is coming from economically advantaged populations. So, expanding that to those who have been historically unrepresented is important for finding out more about our health,” she shares.
But what keeps people awake at night besides artificial lighting and the noisy disruption of the city nightlife? E-readers and smartphones in bed suppress melatonin; some studies say the blue light emitted by our smartphones is even worse for us than other types of light. McKinnon stresses that, “When sleep researchers give advice for insomnia, trouble sleeping, and trouble waking up, getting bright sunlight in the morning is a crucial part of that. It’s that light-dark balance; you should get the bright sunlight during the day, and conversely, after sunset, you want that darkness.”