‘I definitely got a little loopy’: the writer who spent a week underground studying sleep

Sleep deficiency tugs at our personal happiness, costs the US economy $45bn a year and takes an enormous toll on our health. For her extensively researched book, The Inner Clock, the environmental science writer Lynne Peeples spoke with some 240 scientists, chronobiologists, athletes, astronauts and “chrono-coaches” (yes, that’s a thing) and even embedded in a windowless underground Arkansas bunker in order to experience body-clock disruption first-hand.

For anyone who suffers from sleep issues, gets thrown off by daylight saving time or has a variable work schedule, Peeples’ insights come as a bracing slap in the face. Not getting the rest we need can impair our physical and mental health – sometimes to drastic degrees.

The Inner Clock shows up modern life’s chaotic and often dangerous effects on our circadian rhythms – tempos set by little internal clocks within our bodies that govern our sleep, energy, moods and metabolism. Peeples, 44, spoke with the Guardian about her research and how she is resetting her own habits.

In your book you talk about a binary that is familiar to most of us: early birds versus night owls. But you put yourself somewhere in the middle, identifying as a “dove”, a term that was unfamiliar to me.

I don’t drift quite as late as some people who are night owls and I’m also not naturally a super early riser, but that doesn’t mean I can’t get thrown out of whack. I grew up in Seattle, where winters are dark, and we’re at a high latitude, so those days are also really short. My high school started at 7.25 in the morning and I was getting up for weeks and weeks of the year in the dark, and getting to school in the dark. I would have sports practice in the gym after school, so often I wouldn’t see daylight. And then I went to college in Minnesota, and the winters there were bitterly cold but the days were bright and sunny. I remember feeling better and like my mood was lifted.

While reporting this book, you spent over a week in a bunker in Arkansas, accompanied by nobody but a fruit fly. How did you get there – you just went on Airbnb and searched the word “bunker”?

I did. And that’s how I eventually found this Arkansas place. I just wanted to see who I really was without all of the outside stimulus and information. I covered my body with devices to measure everything – temperature, heart rate, blood glucose and so on. At some point, about halfway through, all my body clocks lost coordination with each other, and they were all beating kind of to their own drums.

The whole experiment sounded kind of claustrophobic and awful.

It really wasn’t – I mean, maybe to a point, but it was kind of nice to check out and not have any responsibility to email or text for a while. I definitely got a little loopy. But I wanted to hide from daylight and learn about my own circadian rhythms. I was hoping to do it near Seattle, where I live, but the only bunker I found online was in Arkansas.

My body all fell out of sync. And I just wasn’t feeling as well either – my stomach felt off and my mood was swinging a lot. When I went to look back at the data, I saw that my body had flipped. I thought it was morning when it was night, and vice versa. For instance, I was having “breakfast for dinner”, which I thought was cute, but it was actually was breakfast time.

Your book touches on the health risks posed by circadian complications, when our internal time and the world we live in are less and less in sync. Which utterly terrifies me, as someone who often sleeps five hours a night.

From the studies coming out, you’re at higher risk of developing a metabolic disease. If you’re eating at all times, or at odd times, you’re going to raise your risk of diabetes, obesity and potentially heart disease. There are studies linking circadian disruption to cancer, depression, dementia and Alzheimer’s.

This is really still somewhat early days, but they’re finding a correlation. You’re not going to go into a doctor’s office right now and expect them to immediately identify circadian disruption. It’s something that’s going on inside [our bodies], behind the scenes.

A big theme in your book is the effects of artificial lighting. So if we went back to Little House on the Prairie days, we would have an easier time of resetting?

We would. That’s not to say we should all go backwards. I’m into modern plumbing and everything.

The importance of lighting is the backbone of your book. You map out the societal inequities: people who live in urban areas are exposed to 24/7 lighting, while those who live in the country have better access to natural cycles.

Lighting disrupts our circadian rhythms. We could just turn the lights off at night. It’s the easiest thing we can do, and it saves energy.

Related: ‘Big light has no vibe’: why you should ditch overhead lighting

One of the most fascinating details in your book was the part about how inanimate objects like iceberg lettuce have their own circadian rhythms. They, too, respond to light and darkness.

Their clocks are ticking, ticking, ticking when we pluck them or cut them out of the ground. And they’re still counting on light and dark cues to keep ticking. When we put a piece of produce in a supermarket, and it’s left under lights all day or when we put it in the fridge, where it’s dark all the time, its rhythms are going to weaken too.

You bring up the term “social jet lag”, and I wonder if you can explain that.

It’s the lack of coordination between your natural rhythms and society’s clock. It’s the five-day work week or school week, when we’re forced to get up before our inner clocks would want us to. And then you’re out late Friday night, and you don’t go to bed till one in the morning, and you sleep until 10. You sleep in late again on Sunday and are forced up early again on Monday. You’re basically time traveling. It’s all hard on the body.

How have you set up your home and life as a result of your reporting?

I’ve got about 12 dimmable electric candles in my living room area. I turn them on when the sun goes down, and it’s cozy. And during the day I sit by the window – even when it’s cold out.