The Surprising Link Between Short Sleep and Longevity

I recently came across a surprising statistic that Japanese people sleep on average 352 minutes or 5.8 hours a night. Yet, there are people with the highest life expectancy of 85.27 years. South Koreans also sleep on average 6 hours a night with a life expectancy of 84.5 years. That's 5 years longer than people in other Western countries. I'm not saying that this is the reason why Japanese and Koreans live so long or that everyone literally sleeps 6 hours there. But it's just surprising given the fact how much people say that you need to sleep 8 hours every night to be healthy. So I decided to dig up the research again and look at how much sleep do you actually need and how many hours of sleep is associated with the lowest mortality and the greatest longevity. The general recommendation for sleep is 7 to 8 hours for adults. However, many of the observational studies find that the lowest mortality risk is actually seen at 7 hours per night. A 2016 meta analysis of 35 studies saw that 7 hours per night was associated with the lowest mortality risk. And sleeping less than 6 hours or more than 8 hours was associated with increased risk. Interestingly, sleeping over 8 hours is associated with a much higher risk than sleeping less than 6 hours. That's because people who sleep over 8 hours usually have some sort of a disease or sickness like cancer or they're near their deathbed. Long sleep is associated with increased risk of diabetes, heart disease, and stroke. This is the reason why sleeping 7 hours appears to be associated with the lowest mortality and why Japanese people can get away with sleeping only 6 hours per night. Healthier people need less sleep and they're not going to sleep over 8 hours on a regular basis. It might happen every once in a while, but not regularly. Japanese people are extremely healthy compared to Americans or other Western Europeans. They have an obesity rate of only 4.5% compared to the 40% of the USA. But this can't be the only reason why Japanese get away with less sleep because sleeping less than 7 hours is actually associated with a higher risk of obesity and it coincides with a higher BMI, at least in the United States. But even amongst the Japanese, sleeping less than 7 hours is associated with a higher odds of obesity. But the same applies to sleeping over 9 hours. Coming back to the sleep duration across countries, you can find Finland with 443 minutes or 7.4 hours of sleep per night. And their life expectancy is 81.2 years, which is still quite high and one of the highest in European countries, but it's not as high as Japan. You also have Saudi Arabia with a sleep duration of 362 minutes or 6 hours, the same duration as Japan, but their life expectancy is 79 years, which is not very high. And it's actually lower than the United States. Both Saudi Arabians and Finns are much unhealthier and they have an unhealthier diet than Japanese people. And it shows in Saudi Arabia about 25% of people are obese, whereas it's 26 to 30% in Finland. So, it might be that just a general healthier lifestyle and diet in Japan might reduce their total sleep demand or it makes up for their shorter sleep and still enables them to live significantly longer than other countries. They can sleep 6 hours without gaining weight or shortening their lifespan because of their healthy diet and healthy lifestyle because Japanese people, they're not massive exercises either. To be honest, that's the best advertisement I've seen about the importance of a healthy diet. specifically something similar that the Japanese and Koreans eat, which is very light, small portion sizes, lower in calories, not very fatty, not very sugary, lots of soups, etc. If you're eating junk food and highly processed food, your body experiences higher inflammation, which means you need to sleep more to fight that inflammation. It probably doesn't even have to be pure McDonald's or pastries. The traditional cuisine that's very rich and high calories, such as in Saudi Arabia and Finland, can also be harmful in that regard by increasing some inflammatory status. Obviously, these statistics are very complex and they don't apply to each individual specifically. So, we can't make any conclusions about an individual's specific health based on these statistics, but you can draw some rough conclusions about patterns of behavior and patterns of eating. Another big reason why Japan has a lower sleep duration is that Japanese people are older. The median age in Japan is 49.4, which means the Irish Japanese is nearly 50 years old due to their very low birth rates. Finland's median age is 43.2. two, which is 6 years younger. Younger people and children sleep quite long, up to 10 hours a night, which would explain the reason the average sleep duration in Japan is low. There's not enough children who increase the average sleep duration of the country. Older people, on the other hand, sleep less. There's an age related decline in sleep duration and the amount of deep sleep that you're getting. This is generally not a healthy thing because you still need to sleep. But sleeping shorter doesn't appear to be a big problem for the Japanese people because they still live very long. one of the longest living people in the world. What I would still recommend for people over the age of 70 is to take larger doses of melatonin because natural melatonin production plummets with age. This would help with sleep and provide other anti-inflammatory benefits. Japanese people are also nappers. One study found that 21.2% of Japanese men and 17.1% of Japanese women take a nap over four times a week. That's quite frequent. Spain, which is known for taking afternoon siestas, has only 18% of people taking naps over four times a week. But Spain's average nighttime sleep duration is also 6.9 hours, 1 hour longer than the Japanese. And Spain's life expectancy is 83.94 years, which is less than half a year shorter than Japan. So Japanese people taking very frequent naps probably helps to make up for their shorter sleep at nighttime. They still don't get 8 hours of sleep during the day. They might sleep only 20 to 30 minutes. So, they get on average 6 and 1/2 hours of sleep during the 24-hour period. There is compelling research that taking short naps in the afternoon is associated with better health outcomes and lower rates of mortality and heart disease. This 2025 study saw that taking short naps of less than 30 minutes was associated with the lowest mortality risk, even when taken over three times per week. Taking long naps for over 60 minutes for over 3 days a week was associated with an increased mortality risk. Japanese have short power naps for 20 to 30 minutes even in public spaces and workplaces. So they sleep 5.9 hours in the night and take a 20 to 30 minute nap at work. What the study also found was that people who engaged in more than 150 minutes of physical activity per week, the sleep duration associated with the lowest mortality risk was 7 hours, not 8 hours. Among those not meeting the physical activity requirements, the sleep duration with the lowest mortality risk was between 6.5 to 7 hours. So, if you exercise, you might need a little bit more sleep to help your body to recover. And exercise also raises inflammation in the short term, which increases your sleep demand. I've noticed that myself whenever I don't exercise, I sleep less and I feel very refreshed with only 6 hours of sleep. Whereas, if I have a hard workout, I need at least 1 hour more sleep to feel 100% recovered. All right, let me give you a full breakdown of how much sleep would you actually need. The optimal sleep duration for the lowest mortality risk is 7 hours. that's been consistently shown. You don't have to force yourself to sleep 8 hours or more because the data doesn't support the idea that longer sleep is healthier. If you feel normal and recovered and your vital markers are good on less than 7 hours, then don't freak out. But if you do feel tired with less sleep, then you need to sleep more. Just follow how you feel. If you exercise or have an unhealthier diet, you need more sleep to recover. You should still exercise obviously for the other benefits, but you should also eat a cleaner diet. Take short power naps for 20 to 30 minutes frequently. They're very healthy and appear to be associated with a lower risk of heart disease and death. Maintain sleep regularity to optimize the quality of your sleep. Going to bed around the same time is associated with better health and lower mortality. Overall, sleep is very important. You can't live without sleep. And sleeping only 4 hours a night is probably going to kill you faster. But you don't have to force yourself to sleep 8 or 9 hours a night. 7 hours appears to be already optimal. If you want to learn about how to fully optimize your sleep and recover faster, then check out my full evidence-based sleep routine