by Paul Bogard
And, in going to battle every night with our need for sleep, eventually our body is going to lose.
“The question ‘Why do you do this work?’ is kind of a moot one, isn’t it?” I say to Lawrence after we’ve made our first stops.
“It’s true, they don’t see that they have an option in this economy,” he says. “But most people are doing it for the sake of their family and their home life.”
I hear this from several night-shift custodians, including Lawrence (“I love it,” he claims of working all night. “It’s the only way of life I have found so far that allows me to meet all the needs of my family”). I hear especially from women that their main reason for working at night is that they can be with their family during the day. As one woman tells me, “It plays havoc on your body. I lost thirty pounds from the start, and I didn’t have it to lose. It makes your body feel run-down, tired, exhausted. But I also have a family, and so I try to get back to a regular schedule on the weekend.”
“Have you adjusted?” I ask.
“I don’t think I ever will.”
Ironically, women who work the night shift actually have much higher work-family conflict than women who work only days. You might think that their being home during the day would help smooth things for their families, but most people working the night shift have spouses who work the day shift, which dramatically cuts down time spent together. Even when they do spend time together, the spouse working the night shift is often exhausted. Although some whom I spoke with joked about it, like the nurse in Nevada who told me her husband thought they got along better because they didn’t “see each other as much,” I heard the admission that the situation was “difficult at times” far more often.
“I worked first shift for sixty-five years,” says a gray-haired man named Mr. Singletary. “But now I’m supposed to flip this body, make it turn into the graveyard shift—and now I know why they call it the graveyard shift. When everybody’s asleep, I’m wide-awake. Eating habits, out the window. I don’t have breakfast no more—when I’m getting home my wife is already gone to work.” Mr. Singletary reminds me of my grandfather—it’s not only his age but how he chuckles to himself after nearly every phrase. As though Lawrence and I aren’t standing a few feet away, Mr. Singletary wonders aloud about how he will find time to mow the church lawn, the local football field, and his own yard.
“You’re just going to have to give up sleep,” I joke.
“I’m going to have to figure out something,” he says, sighing. “I’m not sure how I’m going to do it.” And then, more quietly, “God will show me a way out of it. He will show me a way.”
Like many of the other custodians working the night shift at this well-known southeastern university, Mr. Singletary is African American. The custodian who tells me he’s “used to it” because he worked from 5:00 p.m. to 5:00 a.m. for years at the local peanut factory? African American. The woman who tells me that for eighteen years she’s existed on sleeping two or three hours a day? African American. The man who tells me simply, “Some people’s not cut out for third shift”? African American. When I ask him what it feels like, he pauses. “You ever worked third shift before? Okay, well. Wouldn’t do me no good to explain it to you, then.”
Here lies another truth about night-shift work: Certain segments of our population bear its burdens more than others. Nearly 20 percent of African Americans in the United States work the night shift, for example, and more blacks work it than whites, Hispanics, Latinos, or Asians. In addition, poor and disenfranchised city neighborhoods are often brightly lit in an effort to deter crime, and poor and minority populations disproportionately fill the increasing number of third-shift jobs. As scientists affirm the connections between the flood of electric light at night and a long list of health problems, working the night shift stands to become another public health issue that certain segments of our population will deal with—and suffer from—more directly than others.
By the end of my time with Lawrence, nearly 1:30 a.m. on a day on which I woke at 7:00 a.m. and worked my usual schedule, I have grown so tired I can’t concentrate on either my questions or the custodians’ answers. I can’t keep from yawning, either, and when I do they are jaw-stretching yawns that bring tears to my eyes. I’m reminded of a nurse I know who, when she drives home after working all night, closes her ponytail in her car’s sunroof so that her head will be jerked upright if she falls asleep at the wheel.
Not to take anything away from exhaustion, obesity, diabetes, cardiovascular risk, or higher rates of abortion, miscarriage, substance abuse, and depression (to name just a few possible night-shift-sparked sufferings), but it is cancer that scares most of us most, and cancer that may finally get our attention about light at night.
An increasing number of studies over the past two decades have made a compelling case for a link between light at night and cancer, especially hormone-influenced cancers such as breast and prostate. Specifically, it seems that light at night disrupts—that is, suppresses—the body’s production of melatonin, which the human body produces only in darkness, and that melatonin plays a key role in keeping these types of cancers from growing. Light from the moon, stars, candles, or fire—none of these are bright enough to cause this disruption. Only electric light does the trick.
This means, for example, that if you get up in the middle of the night and flip the bathroom light switch, no more melatonin. You may be thinking “toilet seat,” but inside your brain your pineal gland is thinking “daylight!” None of the scientists I spoke with is willing to say light at night gives you cancer—it will take more studies and data, more thought and consensus. But the research seems headed in a clear direction.
The first published suggestion of a connection between light at night and cancer came from Richard Stevens in 1987. Stevens tells me he literally saw the light when he woke one night in his Richland, Washington, apartment. “I realized that I could almost read a newspaper from the streetlight coming in,” he says. “And just by luck, I knew a guy in town who was doing work on light and melatonin, and then I knew another guy doing work on hormones and breast cancer in Seattle. And that was it. I asked myself, What is a hallmark of industrialization if not lighting the night?” This moment led him to develop the light-at-night theory for breast cancer, which he describes in the following way: “increasing use of electricity to light the night leads to circadian disruption which accounts for part of the breast cancer burden in the modern world and rising risk in developing countries.” In turn, this theory led him to two key predictions: Because they are exposed to artificial light through the night, women who do shift work should be at higher risk, and, conversely, blind women should be at lower risk. Both predictions have since been supported.
In the early years, Stevens found more skepticism of than support for his theory, a period he describes in his article “Electric Light Causes Cancer? Surely You’re Joking, Mr. Stevens,” a well-told chronology of the “journey… from electric light to breast cancer.” But in 2001 he was among the authors of two papers in the Journal of the National Cancer Institute that showed “a significantly increased risk of breast cancer in women with a history of night work,” an event that Stevens calls “the turning point for the LAN/breast cancer topic.”
Next, two important developments took place, one that would demonstrate the dramatic effects on tumor growth by the presence of melatonin in our blood, and another that would show the precise wavelengths of light that maximally suppress melatonin.
In the first, David Blask did key research, published in 2005, showing that human blood taken during the night in the dark (and therefore high in melatonin) slowed the growth of human tumors growing in rats, whereas blood taken during the day or at night after exposure to light (and therefore low in melatonin) did not slow the growing cancers at all. The consequences are that suppression of melatonin by exposure to light at night may then increase cancer growth rates if you already have a tumor, or may increase the risk of o
ne developing. “This experiment,” explains Stevens, “is as close as ethically possible to a direct test of whether LAN influences breast cancer growth in women.”
A few years prior to Blask’s work, in 2001, research spearheaded by George (Bud) Brainard of Jefferson Medical College determined the wavelength of light that most affects melatonin production in human volunteers to be blue. This finding complemented an amazing discovery, published in 2002, by David Berson and colleagues at Brown University, of a new photoreceptor cell in the ganglion cell layer of the retina—a part of the eye that was thought not to be light-sensitive—the first such discovery in 120 years. When isolated in a petri dish, this cell also most strongly responded to blue light. Because we have studied the human eye for thousands of years, we thought we knew everything about it, including how it detected light. Essentially, we believed that there was only one pathway through which light was directed to the body, and that this was through the rods and cones that give us vision. But Brainard’s experiments were inconsistent with this understanding; there had to be a whole new way of detecting light for the circadian system, separate from vision. The newly discovered cells, called intrinsically photosensitive retinal ganglion cells (ipRGCs), had nothing to do with vision per se but rather were dedicated to detecting light to determine the time of day and time of year, and in the process, resetting circadian rhythms. Brainard found that while “any sort of light can suppress melatonin… light composed of blue wavelengths slows the release of melatonin with particular effectiveness.” The new photoreceptor cell’s peak sensitivity turns out to be at a wavelength of about 480 nm, which happens to be the color of a clear blue morning sky. In evolutionary terms, that our body’s ability to know day from night is highly sensitive to this wavelength makes perfect sense.
The problem is that everywhere in the world—in our computer screens and tablet screens, in our indoor and outdoor lighting—we are using more and more blue light. More than 1.5 billion new computers, televisions, and cell phones were sold last year alone, and incandescent lights are being replaced by more energy-efficient, and often bluer, LEDs. “Blue” light refers to one place on the spectrum of light, and we see (or sometimes don’t—think x-rays or infrared light) different colors of light because of their different spectral makeup. Unfortunately, it turns out that the wavelength of light that most directly affects our production of melatonin at night is exactly the wavelength of light that we are seeing more and more of in the modern world.
If these links prove true, the ramifications could be huge. For example, imagine if we can link the blue light of computer or television screens at night to breast cancer, the causes of which continue to befuddle scientists. Each year in the United States alone some two hundred thousand women are diagnosed with breast cancer, and some forty thousand die. Says Richard Stevens, “It could be twenty or thirty percent of breast cancer. I’m not saying it is, but it could be.” George Brainard agrees: “Even if lighting is at the root of only ten percent of breast cancer cases, what we learn may help thousands and thousands of women.”
While these new findings about blue light may in time lead us to change our ways, in the end, researchers caution, the root problem is not the type of light but the fact that it’s there. As Steven Lockley says, “People are now concerned about the type of light, rather than being concerned about the use of light at night overall. They’re missing the point. Blue LEDs or white LEDs have a place. Other lighting has a place. But all of it has to be reduced at night. They’re worried that if we change to LEDs, lighting will become a problem. The problem’s there already, however, because our nights are not dark.”
While night-shift workers suffer the most extreme examples of circadian disruption, light exposure at night has the potential to affect everyone living in industrialized society. For example, Schernhammer found that it’s not only women who work the night shift who have lower levels of melatonin but women in general (and men—other studies have linked LAN with increased rates of prostate cancer). That is, even if we’re not working the night shift, we are staying up later, exposing ourselves to light at night in ways that our bodies haven’t evolved to handle.
The question is how much—or little—light does it take to confuse our circadian rhythms and disrupt our production of melatonin? Are we endangering ourselves even in our homes, even in our bedrooms? Does merely sleeping with artificial light coming through the window or seeping under a closed door spell trouble? Researchers warn that while it has been shown that levels of light produced by bedside lamps, computer screens, and tablet displays are detected by the brain and suppress melatonin, the direct evidence linking light pollution and health is in its early stages.
When I ask him about this, Stevens agrees. “Before 1980 it was thought that humans were different, we were not susceptible to light at night no matter how bright, that melatonin rhythm was just fine. Then in 1980 there was a seminal paper in the journal Science that changed everything. But that was with very bright light. The amount of light at night that the scientific community agrees can suppress melatonin in people has been going down, down, down. But we don’t know whether chronic very low light coming in from the streetlights or whatever, we don’t know what effect that has.”
We haven’t begun to understand all of the health effects of our living amid the flood of light at night, a flood most of us are so used to we don’t question it. But if we could clearly say that electric light at night gives you cancer, or at least harms you, the whole situation changes. I asked Harvard’s Lockley if he thought that, based on what we know now, it was fair to think that these connections exist.
“I think that is fair. As a scientist, I can only report what is found experimentally, and those experiments have not been done. And that’s why I use the terms ‘possible’ and ‘likely.’ But the multiple shift-work studies that have shown a link, coupled with the laboratory data, are good evidence to believe that there is a link even in the absence of an unequivocal clinical trial. The WHO [World Health Organization] classification as a probable carcinogen is as high as you can get without actually proving, beyond a shadow of a doubt, that shift work causes cancer.”
Of course, we know some causes of cancer. We have no doubt that asbestos causes mesothelioma, for example, and that’s why WHO ranks it a Type One risk. Type Two risks—the level at which the WHO has placed shift work—until recently included breathing diesel fumes or being exposed to UV light, both risks that have since been moved to Type One.
Researchers only hesitate to identify shift work as a Type One risk because there simply is not a test we can do to measure its effects absolutely. Yet we accept the connection between UV light and skin cancer enough to support a sunscreen industry worth some $650 million worldwide, even though, as Lockley says, “It would be unethical to do a study where people are purposely given UV light to see if they get cancer.”
Regardless, he says, “even if I can’t prove to you right now that that light through the window does you any harm, there’s no need to have it. Why take the risk?”
From Interstate 694 in the outer suburbs north of St. Paul, Minnesota, I exit toward the bright red “Emergency” spelled across a dark brick hospital building. Under the parking lot’s high-pressure sodium pink-orange lights a woman pushes a man in a rickety wheelchair, while two teenagers in the car next to me pump death metal out their open windows. In the waiting room, bloated blue ankles emerge from a patient’s print dress, the floor shines with fresh ammonia scent, and three teenage girls giggle in the corner. At the reception desk a small blond woman answers the phones and presses blinking buttons while two enormous male security guards shift their bellies back and forth in tight black uniforms and watch for trouble.
Ever since I’d started reading studies linking night-shift nurses and breast cancer, I’d had the idea to visit an ER. I wanted to hear from nurses what it was like to work at night, and I wanted to ask if they knew about the studies. I thought it ironic that the most well-known c
ases of night-shift workers and the effects of light at night focused on health-care professionals. And, having spent time with campus custodians, I was curious to spend time with people who probably had more choice about working at night than they do, and who certainly were making more money.
Soon the ER doors swing open and my host, Michelle, a nurse for twenty years, takes me first to drop my jacket in the staff break room, where coffee, slushies, energy drinks, soda pop, and cookies stand ready to transport me through the night. This ER has thirteen rooms (though no bed #13) in a square, the nurses’ stations and doctors’ desks clustered in the middle. White coats and tennis shoes, people staring into computer screens. Near the ceiling on each wall a digital bulletin board tracks admitted patients, ranking each 1–5, with 1 meaning “you’re dying,” says Michelle, 2 meaning “you’re really sick” (“chest pains are 2,” she explains), 3 meaning “pretty typical—you need to be seen urgently,” and 4 and 5 meaning broken bones and other minor wounds. The board helps everyone know what things need to be done and are being done, Michelle says. So far tonight, there are no 1s.
A forty-three-year-old mother of two, Michelle is a blond Minnesotan of Norwegian heritage. In comfortable scrubs and a light brown sweater, a necklace of ID cards, and a stethoscope around her neck, Michelle tells me she loves working at night and always has. “Before I had kids, I was a professed night owl. If I was in the middle of a book that I couldn’t put down I would be up all night reading until five thirty in the morning and I would jump when the paper was delivered. I was always a night person.”
The notion of the night owl is one I’ve heard from a number of people, but no one has professed it as freely as Michelle has. (“Not everybody has a love affair with nights like I do,” she admits.) But what about this? Are some people built to be up all night? It turns out there is some truth to the notion (and its morning-loving opposite, the “lark”) in that the length of the biological clock varies somewhat from person to person. For example, some people have a clock that cycles closer to 23.8 hours, while others cycle at closer to 25 hours, with the former tending to be morning types and those with a longer cycle tending to be evening types.
