Why DO we sleep? The answer is bigger than you think

At Drowsy, our ardor for the enigmatic realm of sleep knows no bounds – that much is evident. Therefore, encountering the insights of neuroscientist and sleep authority Matthew Walker in his seminal work 'Why We Sleep' filled us with anticipation. This meticulously crafted piece delves deep into the fundamentals and perks of sleep, drawing from a wealth of research, biological intricacies, and evolutionary wisdom to shed light on the profound significance of rest.

Spoiler alert: It is a key indicator of health and longevity, and Walker starts with a clear message of sleep less, live less. But it’s not all dire – there are plenty of insights and takeaways that’ll help us get the most out of life, with healthy sleep. Here’s a summary:  

Why: small question, big answer

Walker initiates the discourse with a somber portrayal of the perils of insufficient sleep on our health. Yet, he swiftly transitions to depict sleep as the "Swiss army knife of health," encapsulating its multifarious benefits succinctly. Let's embark on a scientific expedition into the realm of sleep.

Rejuvenation Mode: Walker underscores sleep as the ultimate catalyst for resetting our brain and body health daily. It is during this restorative phase that recovery and regeneration unfold, constituting an indispensable component of our overall well-being.

Harmony with Circadian Rhythms: Our bodies dance to the tune of a natural cycle, orchestrated by the circadian rhythm and governed by melatonin. Light signals wakefulness, while darkness cues sleepiness. This rhythm harmonizes with adenosine, a chemical that amplifies our urge to sleep throughout the day. As night falls, our inclination for wakefulness dwindles, while our "sleep drive" peaks—a symphony of biological cues urging us towards slumber.

The Symphony of Sleep Phases: Human sleep embraces an intricate interplay of REM (Rapid Eye Movement) and Non-REM stages. Non-REM sleep fosters memory consolidation and tissue repair, while REM sleep nurtures emotional equilibrium and creativity. Moreover, REM sleep serves as the canvas for dreaming—a poignant mechanism for processing stress, heightening emotional acumen, and unlocking solutions to perplexing problems.

The Toll of Sleep Deprivation: Against this backdrop of sleep's pivotal role, sleep deprivation—or accruing a sleep deficit—emerges as a stark counterforce to its benefits. Attention wanes, emotional reactivity surges, and the specter of cognitive ailments like Alzheimer’s looms larger. Physically, the ramifications are equally profound, elevating the risk of cardiovascular maladies and diabetes, while dampening fertility and athletic prowess.

Why We Sleep

What can we do to get good sleep?

Sleep, an intricate domain, is subject to a myriad of influences across our lifespan. From the demands of parenthood to the disruptions of travel, environmental clamor, and the flux of hormones during menopause – the variables are extensive. However, amidst this complexity, there remains agency over certain determinants that wield significant sway.

Illuminate judiciously. Exposure to artificial light at night, predominantly from screens, poses a threat to our natural sleep rhythms and compromises sleep quality. Of particular concern is blue light, which suppresses melatonin production at a rate twice that of warmer light sources.

TIP: Replace your cool white globes with warm white, and use soft, low lamp lighting before bed. Also, make sure your technology has a night setting that reduces blue light, and try to put the screens away a couple of hours before bedtime.


Pinpointing the Ideal Thermal Environment. Our bodies intricately respond to temperature changes throughout the day, using them as cues for the sleep-wake cycle – cooler temperatures signify the approach of nighttime and promote sleep initiation. Emulating the natural temperature variations of the outdoors while indoors fosters a resilient circadian rhythm, thereby optimizing sleep quality.

TIP: Having a hot shower before bed helps to lower the body’s core temperature which prepares it for sleep. Avoid overheating your room, as a cool room temperature is optimal for sleep.


Manage your consumption of caffeine and alcohol. Caffeine can disrupt your sleep by inhibiting adenosine receptors, masking your body's natural urge to rest. Similarly, while alcohol may induce drowsiness, it interferes with the quality of sleep, causing disruptions in your sleep cycle and hindering the essential REM sleep phase.

TIP: Drink any caffeinated beverages in the first half of the day, then swap to herbal teas that don’t contain caffeine. And remember to balance the deficit caused by a night of alcohol-induced sleep with a better sleep the night after.


Adopt a balanced diet. Consuming excessive carbohydrates in the evening has been linked to reduced Non-REM sleep and an increased tendency to wake up during the night.

TIP: Eat a ‘normal’, balanced diet but avoid eating a heavy meal too close to bedtime. If you are going to eat a bowl of rice or pasta, maybe try having it for lunch instead, and see if your sleep benefits.


Follow a consistent schedule. Walker explains that the circadian rhythm evolved to align us with the earth's 24-hour cycle. Sunlight, being the most consistent cue, plays a pivotal role in regulating our body's rhythm and promoting a steady sleep pattern.

TIP: Aim to wake at a similar time each day and get daylight onto your face to let your body know it’s wake time. Similarly at the other end of the day, go for a walk at sunset to let your body know nighttime is approaching.


Acknowledge your innate rhythm. Walker highlights the evolutionary significance of individuals favoring either late-night activities (night owls) or early morning starts (morning larks). This adaptation likely emerged to reduce the group's exposure to nocturnal predators, as a mixed sleep pattern ensured minimal vulnerability during shared sleep periods.

TIP: Get to understand your natural preference, and work your day around it – no need to feel guilty for sleeping later if you’re a night owl!

Why We Sleep

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