When, in human history, have we ached so much for sleep and unconsciousness? Why, with an avalanche of sleep solutions and a newly sleep-obsessed culture, do we remain in a sleepless epidemic, with around one in three of us sleeping badly and one in 10 having regular insomnia?
The reason is that most of these generic sleep solutions, and our modern lives, defy the basic facts of circadian biology. Humans evolved to be highly sensitive to the 24-hour solar cycle and super-regular exposure to natural light and dark. Nearly all organisms, including humans, have internal daily clocks (circadian rhythms) that control almost every biological system in our bodies, from our sleep-wake cycles and mood and performance patterns to our metabolic, immune and reproductive systems. The bedrock of circadian science is that exposure to regular light-dark cycles provides the daily “time cues” needed to reset our circadian clocks every single day, and not only determines how well we sleep but our very cellular health. We need the sun’s bright blue light in the day to be alert and active, and we need dark to kick-start our brain’s sleep mode and recovery.
Humans today, however, have never been exposed to so much disruption to their circadian rhythms, such as the glaring disconnect between natural solar time and our social “clocks.” We’re taking in light and dark in historically whacked-out, unnatural ways. We blast our eyes after dusk with blue-enriched light from ever-brighter, addictive screens, tricking our brains into thinking it’s still daytime: Netflix binging, checking social media until we pass out.
Work increasingly doesn’t conform to solar time. While 20 percent of people are nightshift workers, reversing their day-night behaviour, gig work is also soaring: Fifty percent of the world’s workforce works remotely at least half the week,4 part of the creeping “always-on” work culture that encourages us to further disconnect from natural cycles. We have a shrinking global world: more airline travel so more circadian disruptions such as jet lag and global conference calls at all hours of the night. Ours is a 24/7 culture (from gyms to supermarkets); light pollution increasingly floods our skies at night; and we’re tied to desks, deprived of natural sunlight in the day. Never before have human environments been such a “lightmare.”
As Dr Steven Lockley, associate professor of medicine at Harvard and one of the world’s top experts on circadian rhythms and sleep, puts it: “The absolute key to healthy sleep and circadian rhythms is stable, regularly timed daily light and dark exposure – our natural daily time cues. Sleep negates light input to the brain, and so keeping a regular sleep pattern will also help maintain regular light-dark exposure. After dusk, when natural light disappears, we must minimise the negative impact of man-made light. In the day, we have evolved to be in the light, ideally sunlight, but if not, high-quality blueenriched indoor light. Period. Given that most of our body systems express circadian rhythms, ensuring proper alignment of our internal circadian clocks, starting with the management of lighting, will have major impacts on human health.”
While we’ve been obsessed with sleep, and trying to get more of it with smart pillows and tonics, it’s the timing of sleep that is absolutely key to getting high-quality, restorative sleep. This means sleeping at the right circadian time, and the only solutions that can actually reset circadian rhythms have LIGHT at the center of them.
So, we predict a major shift in wellness: less focus on all the generic sleep solutions and a keen new focus on circadian health optimisation for not only sleep but for all the brain and body systems that are controlled by the circadian clock. It means that the TIMING of biology will become something we need to measure and manage, and light will be a central part of any solution.
This trend – from a “sleep” to a “circadian rhythm optimisation focus” – takes various forms:
- More people will finally bring circadian rhythm-supporting lighting (and behaviours) into their homes, with an explosion of tunable, biodynamic lighting solutions that sync light with the time of day.
- New technologies such as the Timeshifter app offer personalized jet lag plans with timed light exposure advice as the foundation to help travellers eliminate jet lag, and could have important applications for “timeshifting” shift workers to new work schedules, or even preparing patients for surgeries and treatments to improve efficacy.
- More hotels, wellness resorts and airlines will think beyond generic sleep offerings to offer true circadian solutions for travellers based on their circadian cycle, revolving around the timing of light.
While intermittent fasting is all the rage, people don’t realise that this is also usually a circadian-based solution: It’s natural for diurnal animals such as humans to eat during daylight when we evolved to digest food. More people will adopt the terminology and practice of “circadian eating”: eating when it’s light, stopping after dark.
Dr. Lockley predicts: “Circadian health optimisation – incorporating the type and timing of light -will become more important than ‘sleep’ in health and wellness within the next few years. Medical and technological solutions that will help us realign our internal circadian clocks with each other, and our internal clocks with the outside world, will surge.”
Circadian Biology
The circadian clock in sophisticated life forms (such as mammals) is one extraordinary system. The body’s master clock-controller lives in nerve cells in the brain’s hypothalamus called the suprachiasmatic nucleus, and it’s tuned to the day-night signal by light coming through the eyes and optic nerve. This timekeeping overlord in the brain then orchestrates a network of peripheral clocks that exist in nearly every organ throughout the body (yes, your liver and ovaries have their own clocks), turning on and off a host of clock genes and a wave of timekeeping proteins that rise and fall in a curve in nearly every cell in your body every 24 hours – just like the sun. It’s a magnificent, light-timed cellular choreography that runs on a tight daily cycle and controls almost every body function.
These clocks are in our DNA. Disruptions to our circadian rhythms, from those ever-increasing mismatches between our internal clock and lifestyle, when we override our natural cycles, have significant health consequences, including a higher risk of obesity, diabetes, some cancers, heart disease, depression, gut disorders, allergies, infections, premature aging – and early death. There have been more than 650 studies connecting light to health.
Research also increasingly shows how people are chronobiologically hardwired with genes that make us night owls or early birds – called our chronotype. Researchers estimate about 40 per cent of people are morning or evening types, and 60 per cent are in-between. Our chronotype impacts circadian cycles: Early birds have a faster internal clock, for example, as short as a 23.5-hour cycle, whereas night owls have a slower clock, taking up to 25 hours to complete one cycle. These internal clocks need to be reset, just like a watch, exactly 24 hours each and every day, and the light-dark cycle is the synchroniser.
The Circadian Diet
For decades, diets have been all about what we eat (we’ve scurried from the Mediterranean to the keto diet, etc.) – but the science is mounting fast that when we eat has profound metabolic and weight loss consequences. This new evidence is reflected in the rise of intermittent fasting (Google’s most-searched diet of 2019), which typically restricts eating and drinking to an eight-10-hour window a day.
A host of studies now indicate that alternating between periods of daily eating and fasting has eye-opening effects, with researchers hypothesising that it conforms to the age-old way that humans ate: We experienced periods of food scarcity leading to “metabolic switching.”
But is it the “intermittency” of eating or the fact that the fasting is circadian-synced that is the lynchpin? Because light and dark are the twin gods of our circadian clocks, and humans evolved to digest food in the day – what’s the metabolic (and sleep) impact of eating after dark, which jolts the brain into thinking that it’s daytime? How does matching the timing of eating with our circadian rhythms (with light and dark) impact health? More studies suggest that we should be embracing – and adopting the terminology of – a CIRCADIAN diet.
While intermittent fasting can have people taking their first bite (an important cue that impacts other clocks in our organs) way after the light of morning (say, 1–2 p.m.), a body of evidence shows that calories are metabolised better in the morning than evening: Researchers from Harvard University and the University of Murcia, Spain, found that early eaters lose 25 per cent more weight (and faster) than late eaters. Hebrew University studies show that synchronizing mealtimes with our circadian rhythms leads to significantly more weight loss and reduced insulin resistance than if you ate the same food (of any kind) without a schedule, concluding that a larger breakfast, a medium-sized lunch and small dinner drive optimal results.
The way that the timing of our eating communicates timing info to all the cells in our body is an extremely complex science. A 2019 study showed how insulin resets circadian clocks by increasing the synthesis of period proteins (controlled by the “clock genes”) and how the exposure to light (and its cortisol production) needs to precede the insulin/feeding timing to get the highest amplitude in clock gene rhythm – or optimal circadian rhythms.
And scientists are discovering how the circadian clock directly affects the microbiome (our gut has its own circadian clock): Washington University researchers just discovered an immune cell that sets the clock for the gut, suggesting why circadian rhythm disruptions (those late nights, shift work) are linked to gastrointestinal problems and everything from obesity to colon cancer.
We’re seeing the research on intermittent fasting roll in, but we will see more studies evaluating whether all intermittent fasting is indeed created equal. We need more studies on the impact of timing meals to the light-dark cycle (circadian-synced eating and fasting), and how that impacts insulin levels and fat-burning hormones.
We predict more people will experiment with timing their eating and intermittent fasting differently: eating when it’s light, stopping when it’s dark. The potential of “clock nutrition” on weight loss and metabolic health – and research unriddling the complex interplay of light, our circadian clocks and our microbiota – is an exciting development and just revving up.
The Future
So much research is underway in the emerging field of circadian medicine. Scientists are developing molecules that target proteins that could repair and supercharge our cells’ clock functions, with a new class of circadian drugs that could chemically reset our circadian systems and prevent some of the worst diseases: obesity, diabetes, Alzheimer’s – and even slow aging way down.
As Dr Lockley notes, a future development that will revolutionise medicine and wellness is the ability to measure people’s unique, precise circadian clock state in real-time, maybe even from a single blood, urine, saliva or breath sample at the doctor’s office or at home. A single sample will be able to measure dozens (or even hundreds) of biomarkers at once to pinpoint exactly what our internal circadian time is.
The possibility of a circadian “fingerprint” measurement has huge implications for the timing of medicine because when you take different medicines, have surgery or chemo, and what lab tests reveal, depend intensely on where you’re at in your circadian clock.
University of Pennsylvania researchers are experimenting with pulling data from wearables, phone apps and bio samples to nail each person’s chronobiome fast. Given the skyrocketing circadian science research, wearable-driven apps that could tell us exactly when to take in light and dark, when to sleep and rise, when to eat and exercise, and when we’re at peak and lowest performance, look to be ahead. Humans are horrible at managing time, light and life: They would be a breakthrough.
Consider the new timekeeping app Circa Solar; it has no 12-hour dial or hour or minute hands but instead displays a full day showing the local hours of light and darkness and where you’re situated in light and dark. It might get you fired for missing meetings, but it’s a fascinating thought experiment in re-aligning time to conform to nature.
We need to re-think time, light and human life in deep ways. We need to make hard behaviour changes and stop lighting up our nights with screens and get out in the natural light of the sun. We need to adapt work and school schedules respecting solar time, seasons and age chronotypes. We need to address the lightmare of hospitals where people are supposed to heal; daylight savings; our 24/7 and late-night restaurant and gym culture; the light pollution exploding in our increasingly urban world; and how we light our homes.
Not only if we want to sleep…but because circadian rhythms rule our physical and mental health. We expect some circadian market mayhem ahead (some bright and dim ideas) – but the right timing of light and biology will move closer to the heart of wellness. Finally.
Excerpts from 2020 Wellness Trends, from Global Wellness Summit
