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The High Performance Journal - October 21st, 2025

Ever since childhood, we've been told that 8 hours of sleep is non-negotiable. Anything less we're told is dangerous.

Yet when you look east to Japan, something remarkable stands out: the average adult sleeps just 6 hours a night, yet lives longer and stays slimmer than anyone else in the world.

How can the Japanese routinely sleep less, avoid obesity, and still earn the top spot for global life expectancy?

The answer is not genetics or sleep trackers, but a culture that has fine-tuned the art of getting quality sleep.

In this newsletter, I want to detail how the Japanese can get less sleep than their Western counterparts and still be healthier.

You ready? Let's go 🔥

Dan's Note: While I still recommend 7–8 hours of sleep for most clients, it’s worth noting that optimal sleep varies by culture, lifestyle, and genetics. That said, what works for Japan may or may not work the same for us.

The Japanese Secret To Sleeping Less And Waking Up Fresh

The Sleep-Longevity Paradox

Based on national data, most adults in Japan average 6 to 6.5 hours of nightly sleep, far less than the Western ideal.

Japan's life expectancy in 2025 is 87.1 years for women and 81.1 years for men, which is the highest in the world.

At the same time, their obesity rate remains one of the lowest at 4-6% while the US sits at above 40%.

This defies every Western assumption about sleep and health.

If sleeping less supposedly leads to weight gain, disease, and early death? Why does Japan keep breaking the trend line?

Sleep Quality Over Quantity

The first secret lies in how the Japanese approach themselves. In Japan, sleep isn't about hitting a numerical quota; it's about efficiency and depth.

Studies show Japanese adults often enter deeper non-REM sleep cycles faster due to consistent pre-sleep rituals and environmental cues.

An example would be their mattress:

While Americans tend to equate comfort with softness, Japanese culture sees comfort as alignment.

Many Americans want to sleep on memory foam plush pillows and weighted blankets, while the Japanese sleep on firm futons laid over tatami mats.

This is a practice that naturally keeps us neutral and prevents micro-awakenings that fragment deep sleep.

Another example would be their temperature:

The Japanese prioritize environments that promote thermoregulation. They sleep in lower room temperatures around 60-65°F (15-18°C) and have pre-bed hot baths that trigger the body's natural cooling cascade for deep rest.

Westerners call this biohacking, while the Japanese call this tradition.

Cultural Rhythms That Guard Circadian Health

The Japanese understand that getting a great night of sleep comes down to how you structure your day.

The first thing you notice is that the Japanese sleep cycles are synced to the rising and setting of the sun.

Also, walk through Tokyo or Kyoto at any hour, and you will see constant movement. People are taking the train, cycling, or walking to school or work.

From a metabolic standpoint, the near-constant daily activity maintains high insulin sensitivity and active mitochondria, two of the main reasons they avoid obesity despite sleeping less.

Cultural eating patterns also protect circadian rhythms.

Their meals are structured, moderate, and rarely rushed. Breakfast and dinner tend to be earlier, aligning with their internal clocks, and snacks between meals are minimal.

Their diet is rich in omega-3s from fish, fermented foods like miso and natto, green tea, and fiber-packed vegetables. It is deeply anti-inflammatory and also correlates with one of the ​best diets to eliminate visceral fat.

When it comes to their daily lives of sleep, work, and eating, you will notice that they optimize for routine.

This consistency has been shown to stabilize blood sugar and hormone balance, offsetting many risks tied to mild sleep deprivation.

Siesta Are A Part Of Society

Daytime napping is an accepted part of Japanese culture.

You'll routinely see Japanese people taking a brief rest in public or even at work without stigma.

There's also a recent trend of dedicated nap rooms and sleep cafes where workers will take 20-30 minute power naps around lunchtime to restore focus and productivity.

Research from the National Heart, Lung, and Blood Institute shows naps under 30 minutes improve alertness, lower blood pressure, and enhance memory without harming metabolism.

Studies from University College London link regular 20–30 minute naps to larger brain volume, equivalent to delaying brain aging by 3–6 years.

In fact, in Japan, fatigue carries respect. The concept of inemuri (to doze in public) implies a badge of honor, which is falling asleep because you worked so hard.

Short Sleep, Long Life

A 2025 PNAS cross-cultural study concluded that optimal sleep length varies by culture, environment, and behavior — not everyone’s biology demands eight hours.

For many Japanese adults, 6–6.5 hours is metabolically neutral, making it enough to maintain full recovery given lifestyle design. And when fatigue strikes midday, they nap strategically.

In effect, they’ve optimized recovery systems around modern life, rather than moralizing an eight-hour block.

Also, the biggest drivers of chronic disease (excess calories, chronic inflammation, and insulin resistance) are largely controlled by movement, social belonging, and diet.

Japan is proving to us that a population that supports balanced meals, naps, good sleep hygiene, daily activity, and low obesity can sustain shorter rest without the biological fallout seen in the West.

What Western Sleep Science Might Be Missing

Image courtesy of this ​study​ 

The Western "8-hour rule" stems from population averages, not universality. Think of it as a statistical midpoint, not a personal prescription.

As researchers like Christine Ou at the University of Victoria note, there is no magic number for sleep.

Biological needs differ based on circadian efficiency, diet, and cultural rhythm. In Japan, people remind us that context is everything.

We must also keep in mind that most Westerners live far less rhythmic lives:

• They eat their meals at irregular times.
• They prioritize late-night screens.
• They spend long hours being sedentary.
• They are, on average, obese and metabolically unhealthy

Even for my clients (and myself), I am still going to recommend sleeping 7-8 hours a night because, as Westerners, our lives are so out of sync.

But I will not force this arbitrary number on anyone because I know for a fact that different people thrive off different timing.

What Should You Do?

If you're someone who constantly feels groggy despite "doing everything right," this lesson from Japan may be for you.

The goal isn't to cut your sleep; it's to optimize your ecosystem so your body restores faster. Think quality, not quantity.

Start with these Japanese-inspired habits:

• Cool your bedroom to around 18°C (65°F).
• Take a warm bath or shower about 90 minutes before bed.
• Keep your sleep surface firm enough for spinal alignment.
• Reduce evening light exposure, especially blue light.
• Respect tiredness — stop fighting it, start listening to it.
• Align meal and movement timing with daylight hours.

The good news? You don't have to travel to Japan to make this happen, nor do you need an expensive mattress that cools your bed and tracks your sleep quality.

You can make this happen in your own home.

The Final Word

What's revolutionary about the Japanese approach isn't the number of hours. It's the congruence between their behavior, biology, and beliefs.

One thing you'll notice is that they are about routine. Every small ritual, like that walk to the train, the deliberate dinner, the quiet hot bath, sends signals to your body that say you can rest now.

Sleep is not a stand-alone habit; it’s an outcome of how we live.

When life itself becomes rhythmic and aligned, recovery becomes effortless — and suddenly, even 6 hours can feel like 8.

Onward and upward. 🚀

- Dan

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References

Sleep Duration, Mortality, and Cultural Differences

Tamakoshi A, Ohno Y. Self-reported sleep duration as a predictor of all-cause mortality: results from the JACC study, Japan. Sleep. 2004;27(1):51–54. PMID: 14746362.

Svensson T, et al. Association of Sleep Duration With All- and Major-Cause Mortality in Japan, China, Singapore, and Korea. JAMA Netw Open. 2021;4(8):e2118039. doi:10.1001/jamanetworkopen.2021.18039.

Ou C, et al. Healthy sleep durations appear to vary across cultures. Proc Natl Acad Sci U S A. 2025;122(19). doi:10.1073/pnas.2419269122.

Japanese Obesity and Health Metrics

Ogawa W, et al. The humanistic and societal impact of obesity in Japan. Endocr J. 2024;71(3):273–284. doi:10.1507/endocrj.EJ23-0416.

Igarashi A, et al. Impact of weight loss on obesity-related complications and resource utilization in Japan. J Diabetes Investig. 2025;16(3):e12046468. PMID: 12046468.

Life Expectancy and Longevity Factors

Okuzono SS, et al. Ikigai and subsequent health and wellbeing among Japanese older adults: the JAGES prospective cohort study. Age Ageing. 2022;51(2):afab222. doi:10.1093/ageing/afab222.

Tanno K, et al. Associations of Ikigai as a Positive Psychological Factor With Longevity Among Japanese People. J Psychosom Res. 2009;67(6):577–583. doi:10.1016/j.jpsychores.2009.05.010.

Circadian Disruption Leads to Metabolic Disruption

Fatima, N., Rana, S. Metabolic implications of circadian disruption. Pflugers Arch - Eur J Physiol 472, 513–526 (2020). https://doi.org/10.1007/s00424-020-02381-6

Sleep Efficiency Factors: Temperature, Posture, and Environment

Tai Y, Obayashi K, Yamagami Y, et al. Hot-water bathing before bedtime and shorter sleep onset latency are accompanied by higher distal-proximal skin temperature gradient in older adults. J Clin Sleep Med. 2021;17(6):1257–1266. doi:10.5664/jcsm.9180.

Maeda T, et al. Effects of bathing-induced changes in body temperature on sleep onset latency. J Therm Biol. 2023;114:103512. doi:10.1016/j.jtherbio.2023.103512.

Bader GG, Engdal S. The influence of bed firmness on sleep quality. Appl Ergon. 2000;31(5):485–490. doi:10.1016/S0003-6870(00)00015-3.

Zhang Y, et al. The Effect of Mattress Firmness on Sleep Architecture and Neurophysiology: A Polysomnographic Analysis. J Sleep Res. 2025;34(2):e12071755. PMID: 12071755.

Napping and Cognitive Recovery

Dutheil F, et al. Effects of a Short Daytime Nap on Cognitive Performance: A Systematic Review and Meta-analysis. Sleep Med. 2021;84:179–188. doi:10.1016/j.sleep.2021.09.001.

Leong RLF, et al. Systematic review and meta-analyses on the effects of napping on cognitive performance. Sleep Health. 2022;8(5):529–540. doi:10.1016/j.sleh.2022.05.007.

Japanese Nap Culture and “Inemuri”

Hiremath J. What Are Inemuri Naps? The Indian Express. 2025 Jun 3.

BBC Worklife. Why Overtired Japan Is Turning to Office Siestas. 2022 Feb 24.

Cultural View of Sleep and Modern Adaptation

Samson DR, et al. Are humans facing a sleep epidemic or enlightenment? Variability in sleep duration, efficiency, and circadian alignment across societies. Evol Anthropol. 2025;34(1):47–61. PMID: 11858753.

Kato C, et al. Subjective Symptoms Linked to Sleep Duration and Daily Functioning in Working Japanese Adults. J Psychosom Res. 2023;120:111–118. doi:10.1016/j.jpsychores.2023.111118.

Disclaimer: This email is provided for educational and informational purposes only and does not constitute providing medical advice or professional services. The information provided should not be used for diagnosing or treating a health problem or disease, and those seeking personal medical advice should consult with a licensed physician.