The idea was to see if these changes

8 min readApr 1, 2021

The protocol looked like this: during the first week, I would try to maximise my exposure to daylight by moving my desk next to the window, lingering in the park on the way back from school drop-off each morning, getting outside at lunchtime and trying to exercise outdoors. The second experimental week would be spent minimising my exposure to artificial light after 18:00, relying on candle-light or dim red lighting instead. Then I would combine the two.

In between each of these intervention weeks, I would lead a normal life. These weeks would function as a baseline.

To track my responses, I’d wear an ‘actiwatch’ to measure light exposure, activity and sleep. I’d also complete sleep diaries and questionnaires to assess my sleepiness and mood and undertake a battery of cognitive tests to assess my short-term memory, attention and reaction speeds. On the last evening of each week, I would spend the evening in darkness, taking hourly samples of my melatonin, which is released in response to a signal from the biological clock and therefore provides a marker of our internal time. “Melatonin is our hormone of darkness; it creates the biological night,” says Marijke Gordijn, a chronobiologist at the University of Groningen in the Netherlands, who measured my melatonin levels.

The idea was to see if these changes to my light exposure altered the timing of my biological clock. We were curious to see if any of the benefits predicted by larger, well-controlled laboratory studies would translate into real life.

“We’ve done a lot of experiments where we’ve given a dose of light and seen that it shifts the clock,” says Gordijn. “But if we want to apply those findings to help people, we need to know that it will have the same effect when the environment is more variable.”

And so, on a bright and sunny December morning, I found myself in the local park, inconspicuously trying to work out on the monkey-bars and swings instead of going to a body pump session in the gym. “Mummy, what’s that lady doing?” asked a small boy.

Because it was winter and most people were inside keeping warm, the park was largely deserted. Motivation had been a struggle for me also. It’s hard to overcome the belief that because it’s winter, it will be cold and miserable outside. However, I was reminded of something a Swedish friend used to say: there’s no such thing as bad weather, only inappropriate clothing. And I soon realised that its rarely as bad outside as it may look. Indeed, the more I did it, the more I came to regard getting outdoors in winter as a treat, rather than a chore.

On another morning, I sat in the park with a cup of tea on my way back from dropping the kids at school and got out my light meter. The illuminance of light is measured in lux. On a cloudless day in summer, the light outdoors can reach as high as 100,000 lux; on an overcast day, it can be as low as 1,000 lux. Today, the reading was 73,000 lux.

Despite my best efforts to get more daylight during the intervention weeks, my average light exposure between 7:30 and 18:00 was 397 lux during the first week and just 180 lux during the second. This was presumably because I still spent most of the day indoors, working at my computer, and because the Sun set at around 16:00. The likely reason for this variation was the weather. During the first week, there were 4.5 hours of bright sunshine per day on average, whereas in the second week it was just 0.9 hours. This was still an improvement on baseline weeks, though, when my average daytime exposure was just 128 lux.

It wasn’t only the weather that proved challenging. For the first few nights of the experiment, we slept with the curtains open to maximise exposure to the dawn light. Light at this time is thought to shift the body clock earlier.

I’m not alone in experiencing this problem. In 2016, researchers reported that people living in urban areas of more than 500,000 people are exposed to night-time light levels that are three to six times brighter than people in small towns and rural areas. Those living in areas of more intense light sleep less, are more tired during the daytime, and report feeling more dissatisfied with their sleep. They also go to bed and wake up later than people in darker areas.

After a few days of this, I began closing the curtains and using a dawn simulation clock instead. It was an imperfect solution, as the light from these devices isn’t as bright as daylight. But it was better than nothing.

If exposing myself to more daylight wasn’t hard enough, I also had to eliminate evening light during December, the darkest month of the year. Doing so brought home to me just how useful artificial light is. Cooking by candle-light was a daily challenge, chopping vegetables an outright hazard. I began to prepare meals earlier in the day, which ate into my work time and meant I got less done.

Eventually, I employed another work-around. I installed some smart lightbulbs in my kitchen, that could be dimmed and colour-adjusted using an app on my smartphone. This, of course, created a paradox: to remove the alerting blue light from the bulbs, I had to expose myself to blue light from my phone, so I did it in the daytime to avoid invalidating the experiment. Now our kitchen glowed an eerie red-orange by night. But at least we could cook again.

During my ‘dark weeks’, I was exposed to an average illuminance of 0.5 lux between 18:00 and midnight and a maximum of 59 lux. That was compared to an average 26 lux (and a maximum of 9640 lux — I have no idea what this super-bright, artificial light source was) when I lived normally — although the actiwatch on my wrist wouldn’t have detected any light emitting from my smartphone or laptop during baseline weeks. That’s important, because there’s mounting evidence to suggest that these devices can disrupt sleep.

Another recent study compared people’s responses when they played computer games during the evening on a normal smartphone screen versus one that suppressed blue light. Players felt more alert after using the conventional smartphones and performed worse in cognitive tests the next day, suggesting that their sleep may have suffered.

My pledge to avoid artificial light also made socialising difficult. A few days before my experiment started, a friend invited us over to her house for pre-Christmas drinks in the middle of a “dark week”. When I explained my predicament, she generously offered to let me sit upstairs in a candle-lit room and receive visitors. I politely declined, feeling how I imagine vegans must feel when they’re invited out to a meal at a steakhouse.

Instead, we encouraged friends to come to our house, and so they came: amused, curious, and occasionally concerned about what they might find. One family initially declined our invitation to stay for New Year because they were worried their son might knock over the candles. They changed their mind when I told them they could use the lights in their bedroom. (We kept all candles out of kids’ reach, just in case.)

Once we’d adapted to the challenges, living without artificial light was very pleasant. Conversation seemed to flow more easily, and visitors also commented on how mellow and relaxed they felt in the dim light. Another bonus was that our children seemed to settle down more easily in the evenings, although we didn’t collect any data on this.

But did any of this make any difference to my sleep or mental performance? There was a general trend towards earlier bedtimes during the intervention weeks — particularly during the week when increased daylight was combined with low evening light. On this week, my average bedtime was 23:00, compared to 23:35 on baseline weeks.

As it was December, I had a lot of social commitments, so I occasionally ignored my body’s sleep signals and stayed up later. It’s an issue that researchers often encounter in their studies. “People have social obligations, and it’s very hard for them to follow what their clock is telling them to do,” says Mariana Figueiro, director of the Lighting Research Center in Troy, New York. “We are constantly fighting our physiology.”

Even so, I was significantly sleepier in the evenings during the increased daylight and low evening light intervention weeks. My body also started releasing the darkness hormone, melatonin, some 1.5 hours earlier during the daylight intervention week — and two hours earlier when I avoided evening light.

It is a pattern that’s been seen in other studies. Like me, Kenneth Wright at the University of Boulder in Colorado has long been fascinated by how our modern lighting environment might be affecting our internal timing. So in 2013, he sent eight people camping in the Rocky Mountains of Colorado for a week during the summer and measured how this affected their sleep. “Camping is an obvious way of removing ourselves from this modern lighting environment and just getting access to natural light,” says Wright.

Wright recently repeated the study in winter. This time, he found that participants went to sleep some 2.5 hours earlier under natural lighting conditions but woke up at roughly the same time as when they were living indoors. This meant they slept for around 2.3 hours longer. “We think it’s because people were going back to their tents earlier to get warm, so they were giving themselves a longer opportunity to sleep,” says Wright.

Unlike his participants, I didn’t experience a sizeable increase in the amount of sleep I got during the intervention weeks — although there was a slight increase in sleep time and efficiency (the ratio of the total time you spend asleep versus the amount of time bed). However, this didn’t reach statistical significance, meaning it could have been the result of chance. Perhaps it was because I was living in a relatively warm house, which made defying my body clock easier. I also was forced to get up at the same time each morning by my children — who occasionally woke me at night, too.

But when I correlated my sleep with the amount of light I was exposed to during the daytime, an interesting pattern emerged. On the brightest days, I went to bed earlier. And for every 100 lux increase in my average daylight exposure, I experienced an increase in sleep efficiency of almost 1% and got an extra 10 minutes of sleep.

I also felt more alert upon waking during all three intervention weeks — but particularly during the two weeks when I was exposed to more daylight.

The idea was to see if these changes

Written by hajargasihhhhh