Are Japanese growing less heat-resistant?


“Elderly person dies at home of heat prostration.” “High school swimmer succumbs in mid-practice; ambulance called.”

These sort of headlines have become all too familiar lately. In July alone, 31 people died of heatstroke; 18,407 were taken by ambulance to hospital.

It’s hot, of course – still, isn’t there something odd here? Global warming and the heat island effect are facts, but Japanese summers have always ranged from hot to searing, to say nothing of humid, and yet people coped – without air conditioners if you go back 40 years, without electric fans if you go back 60. A sprinkling of cold water on the skin, a bamboo curtain to screen the sun – and life went on.

Why, in this age of artificial comforts en masse, are people suddenly so vulnerable to so universal a phenomenon as summer heat?

“Are Japanese bodies growing less heat-resistant?” asks Shukan Post (Aug 15-22).

Summers undeniably are hotter lately than they used to be, but not enough so to account for the epidemic of heatstroke or heat exhaustion. A more relevant fact seems to be the aging society – more than half of the relevant ambulance calls are from people aged 65 or over. Heat, the magazine hears from Shinshu University Prof Hiroshi Nosei, causes blood vessels to expand, which accelerates blood flow, which activates the sweat glands to produce cooling sweat.

As we age, however, this process wears down. Sweat comes less readily to the elderly. There are more elderly than ever before – therefore, more heatstroke.

Yes, but what of the frequent reports of teenage athletes collapsing on the field? That, too, seems unprecedented.

Here the evidence is contradictory. When experts disagree, the general public find it hard to draw conclusions. On this much at least there is basic agreement: sweat pores form in the first three years of life in response to the environment – more in hot climates, fewer in cold. An average Japanese born in a hot zone would develop some 2.8 million pores; in a temperate zone, 2.3 million; in a cold region, 1.9 million. The more pores, the more sweat.

What was the effect on pore formation of the advent of mass air conditioning in the 1980s? This is where disagreement arises, with some experts saying the influence of air conditioning has been decisive, others saying no. Even granting that young people sweat less profusely today than two or three generations ago – which has not, they insist, been proven – other factors must be considered, not least a degree of enlightenment among high school sports coaches, who used to forbid drinking water during practice, perhaps to heighten endurance, but no longer do.

The worst heatwave in recent memory hit in 2010 – 1,745 people are known to have died from its effects – and yet, says one of Shukan Post’s expert sources, “almost none were children.

So if we’re reading more than ever before lately about heatstroke, the point, says Nosei, “is not that the Japanese have grown less heat resistant but that the number of vulnerable Japanese” – specifically the elderly – “has grown.”

Which, adds Shukan Post, gives the media a chance to fill a slow news season with dire warnings about something which, even when not deadly, is miserably familiar to all of us – heat.

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I understand what this article is trying to do, and thanks for bringing up an issue that is pertinent to everyone. I feel that, in order to add some more nuance and balance to the premise posited in the headline ("growing less heat-resistant"), it is necessary to also represent the other half of the argument. This article briefly but mostly accurately touches upon the physiological and biological factors that appear to be contributing to this heat-weakness phenomenon. But if physiological and biological predisposition were the only factor, then this heat-weakness would not be a new phenomenon, and not worthy of an article. Humans have been humans for millennia.

What the article fails to discuss are the "environmental" factors that contribute to heat-weakness -- one of which is the staggering amount of body-water-depleting synthetic substances in today's processed foods, which was less of a factor in past generations. The liver and intestines require a surprising amount of water (seriously, you'll be shocked by how much) to help them process various chemicals, especially complex sugars (used in pretty much everything now) and synthetic chemicals such as preservatives, texture enhancers and flavoring agents. Note that things like coffee, tea, alcohol and sweet drinks also require significant additional water in order to be processed. This biochemical requirement has been explored in scores of scientific papers. Putting it another way, the average modern human body is struggling with a bit of a water shortage.

Hot weather, for obvious reasons, also requires a lot of body-water in order for the body to cope. So you can see the problem.....

I wish this article had at least touched on possible causes for increasing occurence of heat-weakness, rather than tried to make it just age-based.

17 ( +18 / -1 )

It takes time and effort even for athletes to train for heat conditions. No time, no effort = no acclimation, and some people get hit.

turbotsatJul. 28, 2014 - 11:12AM JST

The professor is probably right. I remember reading in Ken Doherty's Modern Training for Running that it takes a trained athlete several weeks of training in a hot room for two hours a day to get acclimated to running in the heat. And it takes about a week of no exposure to heat to start losing that acclimation.

Now imagine how such acclimation applies to little kids and old people that depend on A/C, no acclimation, sudden exposure.

4 ( +6 / -2 )

As is often the case, turbotsat, you provide a great point of view and good points for consideration. Thanks. Acclimation must also be considered here.

3 ( +4 / -1 )

Thanks, Nightshade :).

3 ( +3 / -0 )

Mad dogs and Engl... Japanese go out in the midday sun.

A large part of the problem is behavioral. In summer you should be indoors between 11 and 2 at a minimum. Despite this you see people outdoors in the heat doing stuff they really shouldn't be doing, like playing sports or working in the fields.

A little common sense would do a lot to bring these numbers down.

6 ( +9 / -3 )

No, it's hotter than it used to be. Average temperatures in Kanto are 3 degrees hotter than they were 100 years ago. There's a whole lot more concrete than there used to be, which makes things even hotter.

9 ( +9 / -0 )

The urban heat-island effect cannot be overstated. Even disregarding the temperature fluctuations brought on by climate change, the fact is that Japanese cities and suburbs are unbelievably crowded and chock-full of concrete, burnished steel, plate glass, asphalt, and engines. It's simple physics.

A 90 F day in a shady grove near a stream is just not the same as a 90 F day when you're trapped in what is essentially an urban convection oven.

7 ( +9 / -2 )

the average modern human body is struggling with a bit of a water shortage.

Thanks for the info, Nightshade, but it sounds like a lot of pseudo science to me. The great mid-90s myth of us all being deydrated unless we drink an extra 6 glasses of water a day has long ago been dismissed as baloney. I am happy to accept that the liver requires a lot of water, but the body is very good at regulating itself and we have a very good way to keep our body fluids in check - our thirst and the bathroom.

Of course it is important to stay properly hydrated, but if you drink fluids (including tea) regularly and are still going a few times a day, you are all right.

What the article above does not explore is changing behaviour and changing demographics. Of course a lot more old people die that 50 years ago - Japan did not have all that many back then. In terms of young people dying, are the numbers really statistically significant?

-1 ( +4 / -5 )

I'm wondering about if taking an ofuro nightly will make one prone to sweat and feel more exhausted in the heat. Anybody know?

-1 ( +1 / -2 )

Pandabelle and LBW2010. I believe you are right on the money.

2 ( +3 / -1 )

I'm not convinced that people are physically less robust than they used to be. I think these heat stroke figures are down to a number of other factors:

Heatstroke being more widely reported than in yesteryear, The population has increased, The population has become concentrated in large urban areas with little greenery to absorb the heat. Aggressive use of aircon meaning that people frequently move from cold to hot environments and vice versa, affecting people's ability to acclimatise. Faster paced lifestyle demanding activity during all parts of the day. No afternoon snooze under a riverside tree anymore.
4 ( +5 / -1 )

Heatstroke is purely a behavioural issue. You have to actively do something to get it, and force yourself to be in the sun more than your body is telling you to do.

Does this sound like something the Japanese would do? Absolutely 100% yes.

Are the Japanese, as a subset of humans suddenly, after millions of years of evolution, hyper-evolving against the flow of evolution to be LESS suitable to their environment? No, of course not.

Are they continuing to do that Japanese thing of ganbarouing against all reason and logic, to the point where they are dropping dead with heat stroke. Yes, obviously they are.

0 ( +5 / -5 )

The elderly here don't drink enough. FIL would have coffee in the morning, a couple of glasses of mugicha a day, and one cup of hot tea at lunch and dinner, I doubt that it totaled much more than a liter per day. The women are worse, they drink very little, reasons given being not wanting to use an outside restroom, and not wanting to sweat. They are already very dehydrated before summer get here, it's a recipe for disaster. In addition, from the late 70s onward, many elderly don't recognize thirst, and they also don't sweat much...and their core temperatures rise.

7 ( +7 / -0 )

...but the highschool baseball coach said "Konjo ga tarin!!". Even the former Hiroshima Carp coach said that it was good to "make them sweat from the stomach"... ;-)

3 ( +4 / -1 )

The way even men walking around with an umbrella to block the sun,shows they are.What's worse,even on cloudy days, they are in full force.

-1 ( +2 / -3 )

I think that A/C abuse is rampant here in Japan (Y_Y) they really keep temperatures too low in shops, which of course upsets our body system. I am lucky enough to live in an apartment that is not that hot and ventilated so I don't use it at all, just before sleeping I set it on 'dry' for 5-10 mins to cool the room off if necessary.

I keep saying they should make a law to set a limit on the minimum A/C temperature permitted in public places; I know that town halls and the like have internal regulations for that, but it's not enough. aside from letting people's internal thermometers work better there are other benefits: if A/C temperatures are kept higher, we will have less hot air pumped out and the cities will be naturally cooler instead of artificially hotter like they are now (Y_Y)

ecology, this mysterious thing [for Japan].

0 ( +3 / -3 )

Japan can be a dangerous place for extreme levels of UV even on a cloudy day. Being a former red hair guy from the far north, if I go outside without applying UV cream within 30 minutes my arms and hands are turning bright red. This can also lead to skin cancer. My mother who lives in Florida for decades has growths removed every year. A reflecting umbrella can help to stop the UV. This summer I've struggled more with the heat, probably because I'm getting older, and one year older than last summer, so I sleep a lot in the daytime and get up at 5am to avoid some of the heat.

3 ( +4 / -1 )

Are Japanese growing less heat-resistant?

This question is an obvious no.

Unless anyone is silly enough to believe hundreds of thousands of years evolution is reversing rapidly.

The fact that many here are dismissing the Iong term trend in global warming is interesting. From this perspective there is still understandable denial as Japanese conservatives still cling to redundant science in face of ovewehming evidence. Allowing public policy to remain unresponsive to the long term trend going forward.

Heat waves are going to become more routine as the oceans temperature steadily rises ^. Re-greening of the landscapes in urban areas is an obvious strategy, but there are many. A focus on green technology and innovation could easily be diverted onto this serious issue addressing localised issues allowing stress to be minimised.

However while the political centre of gravity is still going though what could only be described as a grieving stage ^^ around global warming and subsequent climate change, little will done.



4 ( +4 / -0 )

Definitely behavioural and environmental determinants at play:

Older houses had perfect flow of air from either end, and roofs proportioned to give generous shade (AKA the recently 'discovered' brise soleil) where residents could siesta.

Would we have the same extent of summer heat without AC?

-1 ( +1 / -2 )

These days, people tend to hunker down in their air conditioned homes and are more shut off from their neighborhoods than in the past. In the good old days before air conditioning became commonplace, people would sit outside on their porches to cool down and would interact more with their neighbors. Not so today, and the elderly, as an unfortunate result, suffer the most from this lack of neighborly interaction.

3 ( +3 / -0 )

I doubt most of the elderly people even use AC so I don't think that is an issue. Japanese like to blame the AC for everything though. I just went to a massage clinic and could overhear all the women going in there talking about the AC.

3 ( +4 / -1 )

Teachers and coaches are no longer telling kids not to drink, does not mean that kids are suddenly drinking enough. I think kids are still getting heat stroke. They just don't die as easily as old people when they get it. Some kids are actually too lazy to just go get a drink. And some coaches and teachers have switched from saying anything about drinking, but just not letting them have a break so they can.

Also, these teachers and coaches have their routines and schedules, and you just about need to shake a baseball bat at them to get them to change. Students are still not allowed to drink water during class despite them having thermoses hanging right from their desks. Teachers still can't drink during class either, despite needing it more. I suggested having a short water break in the middle of each class in summer. I got incredulous looks. I did not have a baseball bat with me you see....

I tell them schools in hot places in America have air conditioners. Its true. Japanese are smarter about that. Its over-kill, energy waste and counter productive. But why can't they be smarter about water? Seems everybody has to be dumb as rocks about something or they just would not be human.

0 ( +2 / -2 )

The apartment with only a door and a balcony window at the opposite end is really hard to get a good ventilation going. Aren't there more of these apartments now than in previous decades? They need air conditioning. But, then there are the stores and trains that are so cold I get a headache. Women use shawls to keep from freezing on the trains. We don't have air-conditioning. It can be rough. We keep the fans circulating, the curtains pulled, electrical appliances off in the daytime, windows open, have pool time for the dogs, do "water chores" like mopping in the daytime if home, sleep on bamboo mats, use water pillows, take cool showers to cool pores, eat shaved ice with frozen fruit and watery veggies like tomatoes or cucumbers, iced teas with a bit of salt, wear hats, wrap necks with frozen ice packs, etc. Evenso, it can be really hard to cope still when it hits over 34 degrees. We are surrounded by concrete and the sun hits in all directions all day. On the really hot July days, we got additional warnings of extreme smog and were told "not to exert oneself and to stay indoors" on the PSA speakers of the town. Yet, the school sports teams heard the same announcements and continued. Today, people are out prepping for the summer festival in the heat but it is cooler than in previous weeks. Just observations.

0 ( +1 / -1 )

I would also blame this on clothing trends. Most Japanese people young and old wear heavy Western clothing designed in much colder European climes out of fashion or habit without really taking into account the weather or season. Office men still wear full black suits, pedestrians jeans and jackets and women dresses even in the summer. It's funny that the nation that basically invented flip-flops and baggy clothes is so repelled by it these days for seemingly no better reason than habit and the misguided belief that it makes them look modern. Down here in Australia the flip-flop which as some people might know was originally the Japanese zori is one step away from being acceptable summer formal wear. I'm already seeing some office workers wearing them at work. Japan needs to collectively re-accept it's traditional wear as fashionable, the rest of world has and besides Japanese traditional clothes evolved explicitly to handle Japanese weather. The refusal to do so is about as intelligent as eskimos deciding to adopt Californian beach wear.

1 ( +3 / -2 )

Googling "Japanese life expectancy", I ran across an article which said that it increased by 13.7 years in the decade after WW II. So, the increase in the number of the elderly, with the likelihood that not all of them can afford to sit in air conditioned rooms during the hottest, most humid days, coupled with the heat-island effect, and the increase in average temperatures, may explain most of why so many elders suffer from heat stroke.

Efforts to ensure that the eldest have access to air conditioning, and do not expose themselves to the worst of the heat and humidity, might reduce the fatality rate due to heat strokes.

Europeans have also reported an increase in the number of heat strokes, if not as drastic an increase, and I wonder if it is not for reasons similar to the Japanese. What I do not understand is why there are not more heat strokes in North America.

1 ( +2 / -1 )

This is my first ever Tokyo summer. I'm from London. I'm unemployed so this summer I have spent a lot of times indoors. I always remember my mum telling me that when she lived in Australia many moons ago her friends always had the windows closed, curtains and blinds down. They opened them up in the evening. I mentioned this to my Japanese girlfriend and she said 'oh no we can't do that here because this is not Australia' so after melting for a few days I tried it (only i kept one window slightly open behind the curtains due to the humidity) and all i can say is closing the curtains and blinds really reduces the heat in the room so much so that i don't always have to use the AC. Finally i showed this to my Japanese girlfriend who at last accepted it was cooler having the room this way (but she still didn't get why I didn't always use the AC) anyway she still won't try it during the day! I am amazed that she has lived her whole life through Tokyo summers and just keeps the curtains open and fires up the AC. She suffers much worse from the heat than me (and i come from a much colder country and have never ever used AC) so maybe relying on the AC all the time isn't the best? Anyway that's what i do during the day here now and it works for me.

2 ( +2 / -0 )


I heard a while back that there is a special word in China for unemployed people who hide at home and keep the curtains drawn, living in the dark. It was a while ago that I heard the joke so I don't remember the details. Something added on to the "sea turtle" term but it doesn't show up in the wiki article on the term. And don't know if Japanese also have picked it up.

But it might relate to why your girlfriend doesn't want the shades down. That and the obvious ("alone with your boyfriend and the shades are down!"). Neighbors can tease too much sometimes. But even more is the thought of what the neighbors think.

("Sea turtles" are overseas Chinese returned to China to work. "Kelp" are those returnees staying at home with no job ('adrift and aimless' like kelp). Both terms are based on puns. )

1 ( +1 / -0 )

It's hotter for sure and there's more concrete. But I also wonder if the number of people at hospitals for this has increased partly because there is so much emphasis and some is psychological?

0 ( +1 / -1 )

the biggest reason for the number of heat stroke cases is the manner of dress. Look around it is summer and over 30 but people are wearing sweaters, jackets, and many layers of clothing. No matter how much you drink if you heat your body through clothing and are older then you are asking for heat related problems. The cities may be hotter but if you are a senior wearing sweats and a jacket you will soon have heat stroke.

0 ( +1 / -1 )

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