“Shift work refers to work that takes place outside of traditional 9-to-5 daytime hours. If you work nights or rotating shifts, you are a shift worker. Many people who work shifts are at risk for developing shift work disorder (SWD) and may experience excessive sleepiness (ES) on the job.” So says the website designed to market the drug known as Nuvigil, sold by Cephalon, a subsidiary of Teva Pharmaceutical Industries, Ltd. Approved by the US Food and Drug Administration (FDA) in 2007 to treat narcolepsy and obstructive sleep apnea and the excessive sleepiness that may come with working a night shift, sales of Nuvigil grew by about 20 percent between 2013 and 2014, bringing in $189 million in the first six months of this year. The company’s online advertising suggests that that “1 in 4” of the approximately 15 million Americans who work outside 9 to 5 hours “may have SWD” and that shift workers may include factory workers, security guards, retail workers, fire fighters, doctors, nurses and other hospital workers, hotel and restaurant employees along with accountants, stockbrokers and “other people with corporate jobs.”

“The main symptoms of SWD are excessive sleepiness (ES) during a work shift and trouble sleeping (insomnia) during sleeping hours,” says the Nuvigil marketing copy. Curious about both the drug and the number of US workers the company might have in its sights as a potential market, I went to see what I could discover.

Working outside daylight hours

When it comes to Americans who are on the job outside of daytime hours, most reports cite 15 million US workers – as do the Nuvigil marketing materials – a number derived from a special supplement to a 2004 Bureau of Labor Statistics (BLS) Current Population Survey. The questions added to this survey to determine hours of the day Americans are working have not been asked since, explained BLS press officer Gary Steinberg. It costs money to add additional questions to the survey, he noted. It’s been 10 years since BLS had funding to ask questions about work hours despite the fact that the labor market has undergone some significant changes in the past decade. It would be possible to compile an estimate from the BLS’s American Time Use Surveys but they look at a slightly different cross-section of the US population than that used by for the BLS employment data used to gauge health of the US labor market. So it turns out there is no officially compiled US Department of Labor figure for how many Americans are currently engaged in “shift work.”

The National Institute for Occupational Health and Safety (NIOSH), however, did have a more recent number to offer, from data gathered in the Centers for Disease Control and Prevention’s (CDC) 2010 National Health Interview Survey (NHIS),   a representative sample of the U.S. population. Based on data for 27,157 adults, authors of a 2013 NIOSH study found that 28.7% of these people worked “an alternative shift.” In comparison, data collected in 2004 by BLS indicated that 17.7% of workers worked an alternative shift. The NIOSH study also found that the prevalence rate of alternative shift work for each industry group was higher than what the BLS survey sample found. “Prevalence rate differences may be due in part to the six year time difference between the two surveys and to the increased use of flexible or alternative work schedules in recent years,” explained NIOSH health communications specialist Stephanie Stevens in an email. While we still don’t have an official discrete number for how many Americans work outside daytime hours, we do have a snapshot that suggests that between one-quarter and one-third of US workers may be on the job outside “regular” business hours.

In the NHIS survey, those working “alternative” shifts tended to be younger workers (43% percent were under 29), and black and Hispanic workers together made up a striking approximate 60% of these workers. Those with a bachelor’s degree or higher, made up only about one-fifth of this workforce. In this survey – done when US manufacturing jobs were at a particularly low level, service industries – food service, security, retail and hospitality – reported higher rates of working these alternate hours than others.

Whether it’s nurses, police officers, long-haul truck drivers, manufacturing or retail workers, shift work is associated with a variety of health risks, not just risks of fatigue-related accidents and injuries. Some studies have found associations between night-shift work and increased risk for metabolic and cardiovascular disease and cancer risk. What these studies do not suggest is that working a night shift itself is a health disorder. The Nuvigil literature filed with the FDA does, however, explain that when diagnosed, the symptoms of “shift work disorder” are consistent with the American Psychiatric Association’s DSM-IV-TR criteria for Circadian Rhythm Sleep Disorder: Shift Work Type.

A dangerous drug?

Which brings us back to “shift work disorder” and the drug being marketed to combat it. Nuvigil is the trade name for a substance called armodafinil, which like its slower acting companion drug, modafinil, marketed as Provigil is, as FDA documents explain, “a wakefulness-promoting agent.” The precise biochemical mechanism by which the drugs work to promote wakefulness, writes FDA, “is unknown.” But the drugs appear to affect dopamine, a neurotransmitter and hormone released by the brain that plays a role in sleep, memory, mood and other neurological functions. In addition to promoting wakefulness, modafinil, writes FDA, “produces psychoactive and euphoric effects, alterations in mood, perception, thinking, and feelings typical of other CNS [central nervous system] stimulants in humans.”

There are many other possible side-effects, including a serious rash that can include Stevens-Johnson Syndrome and various psychiatric symptoms (among them aggression, mania, anxiety, suicidal thoughts and depression), shortness of breath and abnormal heart beat. Nausea, headache, dizziness and insomnia were the most common. Modafinil, writes the FDA, also “has reinforcing properties, as evidenced by its self-administration in monkeys previously trained to self-administer cocaine.” Nuvigil is a federally controlled substance because it can be abused or lead to dependence, says the drug’s medication guide. In contrast, information about the drug posted on the National Sleep Foundation’s website says, “These medications are not amphetamines and are not habit forming.”

Back in 2010, Cephalon applied to the FDA for approval of Nuvigil to treat jet lag but was turned down. More recently the company’s application for approval of the drug for bipolar disorder treatment was also declined. But the drug has been found effective at treating “shift work disorder” as described in published, peer-reviewed journal articles. Yet a close look at these studies quickly shows that many, including one investigating modafinil published in the New England Journal of Medicine – and their authors – were directly funded by pharmaceutical companies, including Cephalon for whom at least one of these scientists (listed as an author on numerous such studies) served as a consultant and speaker.

What is the real disorder?

At this point, what we don’t have a really good picture of is how many Americans work outside daytime hours and how many of these workers might be working night shifts as second or third jobs, which could contribute to fatigue factors if it prevents them from catching up on sleep. And because this information has not been gathered consistently over time, it’s hard to know how it has changed with other overall employment and economic conditions. This data seems important as part of assessing the health effects of working nights and who among US workers is most impacted. That people who work nights are sleepy and have their sleep cycles thrown out of balance does have serious consequences but urging a potentially habit-forming, psychoactive drug – free samples are available – on an economically stressed, overworked workforce, would seem to be a symptom, at the minimum, of a pharmaceutical industry gone awry. Shouldn’t we instead be figuring out other ways to reduce the occupational health risks of work schedules?

Elizabeth Grossman is the author of Chasing Molecules: Poisonous Products, Human Health, and the Promise of Green Chemistry, High Tech Trash: Digital Devices, Hidden Toxics, and Human Health, and other books. Her work has appeared in a variety of publications including Scientific American, Yale e360, Environmental Health Perspectives, Ensia, The Washington Post, Salon and The Nation.