spread to the entire modern world.
Many of us offer up similar reasons for burning the LEDs at both ends of the day. There are not enough hours in the day to do all the things we want or need to do. There’s the daily commute, becoming ever greater as we choose to live farther away from our workplaces or are forced to for economic reasons, such as affordability of housing. Early in the morning or late at night might be the only space we get for me time, away from work or our often overstimulated kids. Our days and our time are so overscheduled that the moment anything extra falls in our lap, we need to borrow (read: steal) time from sleep. We routinely treat our sleep like a credit card in that we feel like we have money to spend, but in reality are barely keeping up the minimum payments.
Is it really that bad, though? After all, recent evidence challenges the notion that our preindustrial ancestral cousins slept more than we postmodern humans do, and that we should be sleeping from sundown to sunup because that’s how Paleo man slept. UCLA researchers followed the sleep habits of three contemporary nonindustrial societies.5 Studying the few remaining societies that live without access to electric light, they reasoned, may illuminate current sleep trends. Absent artificial light and digital technologies, do we sleep longer and better?
At first blush, the research appeared to indicate that these populations spent much more time sleeping than most people living in modern society—seven to eight and a half hours each night. However, further analysis of the data collected revealed that of this time in bed, only five and a half to seven hours was actually spent asleep. This is roughly comparable to modern postindustrial societies.6
This research generated many commentaries and interpretations, the most obvious being that we can all relax—that midnight to 5:30 a.m. sleep routine you have is in fact perfectly normal. “The argument has always been that modern life has reduced our sleep time below the amount our ancestors got, but our data indicates that this is a myth,” said Jerome Siegel, leader of the research team and professor of psychiatry at UCLA’s Semel Institute of Neuroscience and Human Behavior.7 “I feel a lot less insecure about my own sleep habits after having found the trends we see here,” echoed lead author Gandhi Yetish, a PhD candidate at the University of New Mexico.8
I can’t quite embrace that conclusion. The sleep patterns of these tribes seem to work well for them, but based on my work with hundreds of consulting clients, that same amount of sleep doesn’t seem to support healthy outcomes in different, more stressful environments. We industrialized humans burn the metaphorical candle at both ends… with a blowtorch. In the same way that doing a lot of intense exercise requires more nutritious food for full recovery, living a modern life of stress and overstimulation might require more sleep than if we were living like our electricity-free counterparts. Sleep of closer to eight or nine hours might be required if we’re perpetually dealing with the sum total of financial stress, environmental toxins, inflammatory processed foods, social pressure to look a certain way or to acquire more material belongings, and chronic exposure to junk light (reducing the quality of our restoration during time spent in relative darkness, whether we’re asleep or not).
Hello, Darkness, My Old Friend—and Hello, Light
One of the many major differences between the preindustrial societies the UCLA team studied and the sleeping habits of humans in modern societies is less about time in bed and more about the level and duration of darkness we experience before sleep.9 To initiate the high-quality, restorative sleep we all seem to be craving, darkness is crucial. But darkness is something many of us only get once we are in bed and attempting to fall asleep. Even then, given the prevalence of bright alarm clocks, LED lights from the various devices in our bedrooms, light pollution from external sources such as streetlights and vehicles, not to mention both the light and sounds emanating from phone notifications coming in at all hours of the night (“but my phone is my alarm clock”), our supposedly dark bedrooms are anything but.
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While many health experts rightly emphasize the importance of sleep, very few explicitly mention the biological importance of spending time in darkness before we get into bed. One exception is Richard G. “Bugs” Stevens, professor of medicine at the University of Connecticut, who was surprised that time spent in darkness wasn’t a factor in the UCLA sleep study: “… a crucial aspect of the study’s findings has not been discussed in news stories or the paper itself,” he observed in the Washington Post. “People in preindustrial societies spend much more time in darkness than people in the industrialized world.”10 Yet it is becoming increasingly evident to specialists like Bugs that humans have a daytime physiology, triggered by bright natural light exposure, and a nighttime physiology, triggered by the absence of light and exposure to darkness.11 In our daytime state we are (or should be) alert, active, productive, and hungry, driven by key daytime hormones and neurotransmitters such as cortisol, dopamine, and serotonin. After sunset, we transition to our nighttime physiology—our body temperature begins to fall, our metabolism slows, and our readiness and drive for sleep increases as the sleep hormone melatonin surges through our bodies. Except, as we saw in the last chapter, it isn’t a sleep hormone, per se. It’s a darkness hormone.
Come on, admit it. You sidle up to your laptop and watch This Is Us or random YouTube videos for an hour, bathing your eyes in artificial light. But then you get dozy, and finally turn off your television, smartphone, or computer, hoping that slumber quickly follows. Except it doesn’t always, does it? That’s because our daily rhythms are just like the seasonal ones—they require transitional periods. Our bodies are not like light bulbs that are either on or off. Every night, our bodies need to shift from one physiological state (daytime) to the other (nighttime). Absent this gradual transition, we remain restless, becoming progressively more anxious—often to the point that we can’t fall asleep. And when we can’t sleep, we indulge in still more screen time or we indulge in nighttime snacks, getting up to watch TV, have a bowl of ice cream, or scroll on our phone. Or we turn to sleep aids, from mechanical to herbal to pharmaceutical. In 2015 Americans spent $41 billion on white-noise machines, sleep-inducing mattresses, sleep coaches, sleep gadgets and smartphone apps, and other such paraphernalia. By 2020 a BBC Research analyst predicts that number will swell to $52 billion.12
So, what’s the answer? Should we just turn out the lights after sunset and assume that we’ve solved our sleep-related maladies? I wish it were all that easy. First, if you think asking people to give up a favorite food and change their diet is hard, try prying their smartphones and tablets from their hands. Second, and most pertinent, the dark needs to be balanced with the light. Our nighttime physiology is inextricably linked to our daytime physiology, which itself is highly dependent on our exposures to sufficient bright light, particularly in the early morning.
And therein lies the rub. We’re getting too much light at night, and we’re also not getting enough bright light during the day. For many of us, perhaps most of us, our days and nights have become inverted. We are living in dark days and bright nights. I’m not just talking about night-shift workers here, though clearly this is the most extreme example. A significant portion of the population in our modern developed societies work indoors, where exposure to natural light is scarce. This includes retail workers deep inside multilevel shopping malls, office workers without a window seat, factory workers operating inside windowless buildings, medical staff working in hospitals, and air traffic controllers in blacked-out radar rooms. I recently observed that a local bicycle store permanently blacked out their windows (the only source of natural light) just to fractionally increase the shelving space inside by a few square feet. In addition, with the continual rise of urbanism and large sprawling cities where few can afford to live close to where they work, many people must leave home before sunrise and return home after sunset, for much of the year.
But it gets worse. Look around on a bright, sunny morning and you’ll often see a significant number of people wearing sunglasses. You’ll even see this on the not-so-sunny mornings,
