Why Light Time Is The Right Time For Sleep

In 2023, the art of sleep is a billion-dollar industry (in fact the sleep economy is estimated to be valued at 432 billion USD by next year) and by the number of sleep apps, smart mattresses, and night-time teas on the market, you would assume that falling (and staying) asleep was much simpler these days. But unfortunately, regular, good-quality sleep is still a complicated business for many.

It’s been over 10 years since we launched our deep sleep pillow spray and we are proud to be considered pioneers in sleep science, having established ourselves as leaders in the beauty sleep conversation with the support of chronobiologists, neuroscientists, and clinical studies. We know the importance of sleep for a healthy, functioning body and that you cannot ‘fix’ sleep with just one product. While sleep aids are scientifically proven to help, there are many things you can do to signal to the brain that it is time for bed, prepare the mind and body for sleep and improve the quality of your night.

When it comes to improving sleep, we often focus on night-time being the right time, but this World Sleep Day, we want to share some knowledge and important science about the other side of the clock – the ‘light time.’ From when we first see sunlight to the time we drink our coffee, so much of what we do and experience during the day directly impacts the way we sleep at night. The body’s circadian rhythm relies on factors during the day that prepare the body for better sleep, and how and when you are exposed to daylight has a huge effect on your nocturnal patterns.

the science of sleep and the Circadian Rhythm

Our brain is a complex organ that uses neurotransmitters and neuromodulators to start, stop or change the body’s physical and psychological processes. This is two-way communication, and receptors in the sensory organs and all over the body give signals to the brain for a multitude of functions. By choosing to respect the natural and physiological rhythms that control our sleep quality, we influence how our brain and body respond and, therefore, can create the optimal physiological conditions for good-quality sleep.

This World Sleep Day our CEO, Dr. Anna Persaud, is kicking off this new conversation and sharing her advice on how to practice better sleep hygiene and make light time the right time for sleep.

the importance of light

The type of light we view and the time of day we are exposed to it have tremendous effects on our sleep. Getting outside in sunlight for just 10-30 minutes every day (as soon after waking as possible) is not only an uplifting way to start your day, but it triggers the release of dopamine and cortisol levels to peak early in the day. Thought cortisol was related to stress? It is, but it also signals to the body that it is time to wake up, helps boost the immune system and increases our ability to focus, setting us up for whatever the day has in store.^1,2,3

Some tips on morning light exposure:

For maximum effectiveness, do not wear sunglasses when getting your morning light, but protect the eyes by not staring directly at the sun; eyeglasses and contacts are fine.
The amount of time needed outside depends on the weather; on a clear day, 10 minutes is enough, but closer to 30 minutes is best for cloudy or rainy days.

Golden afternoon light is not just the perfect backdrop for photographs - it helps us nod off more easily, too. To counteract the negative effects digital devices and strong overhead lighting has on us during the day, get back outside in the late afternoon to soak up another 10-30 minutes of low-level sunlight. Exposing the receptor pigments in the eye to this lower angle of light helps to anchor the body clock and trigger the release of melatonin which helps us fall asleep smoothly. ^4,5

Switching off the ‘big lights’ in your home, lighting candles, or turning on warm lamps will not only create a calming ambience for the nervous system, but it helps to release melatonin too – the hormone needed to help us get ready for sleep. Bright, artificial lights should be totally avoided between 10pm and 4am, as these reduce sleepiness and can throw off the circadian clock. Even a low level of light in the bedroom has been associated with impaired sleep and metabolic dysfunctions, so it is best to avoid carrying out any tasks in your sleeping space after this time. If you want to read a book or apply some skincare, candlelight or very dim lamps work best. ^6,7

fuel for sleep

We know that sleep plays a significant role in skin health, focus, and stress levels, but it is closely related to our gut health and eating habits too. The two go hand in hand, meaning what we eat (and the times we do so) can affect how we sleep, and how we sleep can affect our decision-making when it comes to food (and caffeine!) intake. Studies show that a healthy gut microbiome can positively affect mental health, whilst sleep deprivation can affect the production of the two major hormones that regulate feeding behaviour. This means that with a lack of sleep, you are more likely to overeat when you do feel hungry .^9,10,11,12

The key here is finding balance. Going to bed on an empty stomach can cause us to wake up during the night or early but going to bed too full, particularly on acidic, spicy, rich, or too-stimulating food and beverages can make it more difficult to nod off. The sweet spot? Eat nutrient-dense foods that make you feel full and satisfied at regular, predictable timings to anchor the circadian rhythm, and avoid eating too close to bedtime as digestion activates the metabolism which triggers alertness.

Hydration is water intake and is essential for optimal brain and energy output. It is important to keep hydrated as much as you can, especially early in the day. Start to taper your fluid intake the closer you get to bedtime, as this can help those who are woken by their bladder have a less-disturbed rest. A warm, comforting herbal tea like valerian, chamomile or peppermint or milky drink is a great way to help wind down before bed.

so, what is the deal with coffee?

That first sip of morning coffee is one of life’s simplest (and greatest) pleasures. If you are a tired mum, busy commuter, or any type of functioning adult for that matter – you may rely on your favourite cup of caffeine to give you some get-up-and-go each morning. This is because caffeine can increase focus, as it strengthens the potential response dopamine has on the mind. ^9,10,11,12

While caffeine is a simple, inexpensive tool to help blow off the cobwebs in the morning and frame your mind for focus, it can adversely impact sleep. Ever wondered why you hit a hypothetical wall come 3pm and start reaching for the nearest kettle or chocolate bar? What goes up, must come down and after that initial spike in dopamine, the levels in your body drop below the baseline and require even more stimulation to reach back to those similar levels. This drop in dopamine can cause sluggishness and affect cognitive performance, essentially you feel tired and lose motivation. ^9,13,14

To balance out the positive and negative effects of caffeine, it is best to enjoy your morning tea or coffee 1.5-2 hours after waking to avoid that afternoon slump. All bodies metabolise and respond to caffeine levels differently, but it is a safe bet to avoid any after 2pm, and for many, that threshold looks more like midday. ^1,15,16

temperature and comfort

Goldilocks was on to something when she searched for the perfect-feeling mattress. Under the right amount of sleep pressure, we can fall asleep anywhere on any surface, but to stay asleep, feel well-rested and avoid body aches, it is essential we find a mattress that suits our height, weight, ease of movement and personal sleep needs. The bed should be considered the most important piece of furniture in your house. Natural fibres like cotton, wool, linen or even silk are best to regulate body temperature and wick moisture from sweat.

To get to sleep and stay asleep, our internal body temperature must drop by 1-3 degrees. A warm shower or bath 30 minutes before bed and putting on fresh, cool bedclothes can kickstart this process, as the body goes through a cooling-off period that facilitates the drop in temperature, and acts as an invitation to sleep hormones, making it easier to nod off. Switching your central heating on to timed so that it begins to cool off an hour before bedtime can keep the room cool and at optimal levels before you hit the (breathable) pillow. ^{18, 19}

turn of tech

We are all guilty of ‘just one more episode’ or ‘one more scroll’ of an evening when we are craving that time to ourselves to ‘switch off’ but consuming content and digital devices close to bedtime will have the opposite effect on our sleep. Many people in the modern world (particularly the young generation) use their bedroom space as an extension of their daytime activities, but for optimum sleep, the bedroom should be a device-free zone. Not only does the light emitted from devices disrupt sleep, but it has a negative effect on connection and intimacy with our partner too.

Using phones and devices that send you notifications can leave our immune system in a state of alertness, which can lead to a racing mind and sleep anxiety and less alertness in the morning when we need it most. Rather than scrolling your favourite apps endlessly, try to put down devices at least 2 hours before bed and even better – keep them out of your sleep space. Instead, opt for a good book (nothing too stimulating or anxiety-inducing!) or a mindful, breathwork technique that uses guided meditation to calm the body and mind.

Want to learn more about how light affects sleep?

1. Terman, J. S., Terman, M., Lo, E. S., & Cooper, T. B. (2001). Circadian time of morning light administration and therapeutic response in winter depression. Archives of General Psychiatry, 58(1).

2. Okamoto, Y., Rea, M. S., & Figueiro, M. G. (2014). Temporal dynamics of EEG activity during short- and long-wavelength light exposures in the early morning. BMC Research Notes, 7(1).

3. The duration of light exposure in the morning and early‐afternoon affects adaptation to night work. (2019). Journal of Sleep Research, 28(S1).

4. Brown TM, Brainard GC, Cajochen C, Czeisler CA, Hanifin JP, Lockley SW, et al. (2022) Recommendations for daytime, evening, and nighttime indoor light exposure to best support physiology, sleep, and wakefulness in healthy adults. PLoS Biol 20(3): e3001571.

5. te Kulve, M., Schlangen, L.J.M. & van Marken Lichtenbelt, W.D. Early evening light mitigates sleep compromising physiological and alerting responses to subsequent late evening light. Sci Rep 9, 16064 (2019).

6. Figueiro, M. G., Steverson, B., Heerwagen, J., Kampschroer, K., Hunter, C. M., Gonzales, K., Plitnick, B., & Rea, M. S. (2017). The impact of daytime light exposures on sleep and mood in office workers. Sleep Health, 3(3).

7. Marqueze, E. C., Vasconcelos, S., Garefelt, J., Skene, D. J., Moreno, C. R., & Lowden, A. (2015). Natural light exposure, sleep and depression among day workers and shiftworkers at Arctic and Equatorial Latitudes. PLoS ONE, 10(4).

8. Taub, J. M. (1978). Behavioral and psychophysiological correlates of irregularity in chronic sleep routines. Biological Psychology, 7(1–2).

9. Morin, V., Hozer, F., & Costemale-Lacoste, J. F. (2018). The effects of ghrelin on sleep, appetite, and memory, and its possible role in depression: A review of the literature. Encephale, 44(3).

10. Broussard, J. L., Kilkus, J. M., Delebecque, F., Abraham, V., Day, A., Whitmore, H. R., & Tasali, E. (2016). Elevated ghrelin predicts food intake during experimental sleep restriction. Obesity, 24(1).

11. Steiger, A., Dresler, M., Schüssler, P., & Kluge, M. (2011). Ghrelin in mental health, sleep, memory. In Molecular and Cellular Endocrinology (Vol. 340, Issue 1).

12. Kun, X., Cai Hong, H., & Subramanian, P. (2019). Melatonin and sleep. In Biological Rhythm Research (Vol. 50, Issue 3).

13. Blask, D. E. (2009). Melatonin, sleep disturbance and cancer risk. In Sleep Medicine Reviews (Vol. 13, Issue 4).

14. Xie, Z., Chen, F., Li, W. A., Geng, X., Li, C., Meng, X., Feng, Y., Liu, W., & Yu, F. (2017). A review of sleep disorders and melatonin. In Neurological Research (Vol. 39, Issue 6).

15. Strandwitz, P. (2018). Neurotransmitter modulation by the gut microbiota. In Brain Research (Vol. 1693).

16. Malagelada, J. R. (2020). The Brain-Gut Team. Digestive Diseases, 38(4).

17. Allen, A. P., Dinan, T. G., Clarke, G., & Cryan, J. F. (2017). A psychology of the human brain–gut–microbiome axis. Social and Personality Psychology Compass, 11(4).

18. Rothhaas, R., & Chung, S. (2021). Role of the Preoptic Area in Sleep and Thermoregulation. In Frontiers in Neuroscience (Vol. 15).

19. Barrett, J., Lack, L., & Morris, M. (1993). The sleep-evoked decrease of body temperature. Sleep, 16(2).