How Night Shifts Perpetuate Health Inequality

Methods for approaching them as safely as possible

The author, asleep (Katherine Wells / The Atlantic)

A man claiming to be a police officer wrote to me recently with an important question, one that’s applicable to all people who sleep:

Dr. Hamblin,

I’m a police officer who works a night shift. … A lot of police departments have a rotating schedule requiring officers to change from nights to days, and back to nights again.

My department keeps us on the same shift indefinitely unless we ask to change. Is there any research or medical opinion about working a rotating night-day schedule versus working a consistent night shift?  ...

I know that is a broad question but any advice is appreciated.


Like most questions about bodies, there’s not one definitive answer that’s best for everyone. But I think Officer Nic is making the right call to stay on nights:

Hamblin on shift work

Night shifts are a health hazard in either case, but for different reasons.

Would it be better not to keep throwing your body back and forth from diurnal to nocturnal? Cleveland Clinic, for one, tells patients both to “avoid frequently rotating shifts,” and also to “decrease the number of night shifts worked in a row.”

What? That’s scary if you have to work nights. Newly discovered health risks of working night shifts keep coming out: higher risks of coronary artery disease, diabetes, weight gain, and some cancers. The International Agency for Research on Cancer has listed night shifts as “probably carcinogenic.” Among people who’ve worked a decade of shift work, their brains show cognitive decline years in advance.

But these findings are almost always in people who do shift work—bouncing back and forth between nights and days. There’s even something called Shift Work Sleep Disorder (or Shift Work Disorder), defined by increased accidents, work-related errors, irritability, or mood problems.

The more we learn about sleep, the more we learn the importance of consistency. It’s not just about how much you sleep, it’s about when. For diurnal people, that means getting up and going to bed around the same time, even on weekends.

Few studies actually compare long-term health effects among people who work some nights to people who work only nights, but the same principle of consistency should apply. If you can manage to get your body into a 24-hour cycle, that’s beneficial, even if it doesn’t correspond perfectly with that of the sun. The idea has to do with chronobiology: Our circadian-phase shifts have evolved to be dependent on light. Cells in the retina send information about light through the hypothalamus. Gene-transcription feedback loops regulate the pineal gland, which secretes the hormone melatonin.

According to the International Agency for Research on Cancer, the additional risk of cancers in shift workers “may be explained by the disruption of the circadian system that is caused by exposure to light at night. This can alter sleep-activity patterns, suppress melatonin production, and disregulate genes involved in tumor development.” But if you get into a consistent groove of night shifts, you should be able to manipulate light with blackout curtains and lamps.

Some employers think they’re doing people a favor by saying you only have to work one week of nights every month. That’s how we did it in the hospital. But maybe it would’ve been better to work three straight months every year. If I were in Officer Nic’s position, purely from a health perspective, I’d choose consistent night shifts.

The downside to that is, of course, that people also have families and lives, and social isolation is this whole other serious health risk factor. So I can’t choose for you. I’ve worked nights in the hospital and known the isolation that comes with it. There’s a sense of being an actual ghost. You get invitations to social things and initially think, yeah I’ll be there. But then you realize you’ll be asleep. If you start to sacrifice sleep to keep a social life up, you can end up equally miserable.

The actual best solution is to make a gradual transition between day shifts and nights shifts—like if you could start and finish ten minutes earlier every day. That would just be a nightmare for scheduling.  And it’s a reminder that most people who have to work frequent night shifts aren’t in a position to be making demands like that. Night-shift jobs and their associated health risks tend to fall to people of lower socioeconomic status, so the risks of shift work tend to go ignored.

In most other areas, if you know that a job is going to involve exposure to a carcinogen, employers are required to minimize that exposure or compensate people according to risk. In the U.S, the Fair Labor Standards Act doesn’t require extra pay for night work. Maybe it should.