Christine Ro , freelance journalist London and Tokyo christineannro{at}gmail.com
Even for a country that regularly battles with extreme heat, summer 2022 has been a harsh one for Japan. Christine Ro examines what will be needed to achieve its ambitious target to break the cycle of heat related deaths
When Jun Kanda was a child, people referred not to heat stroke but to summer lethargy. A common suggestion on hot days was to eat eel.
The idea was that “if you eat something tasty, you gain energy,” says Kanda, now an emergency physician and researcher at Teikyo University Hospital. “But if you talk about heat stroke, you have to have liquids and stay in cool places. So eel, even if it’s good, isn’t going to do anything.”
Kanda believes that heat stroke countermeasures in Japan are relatively recent, as extreme temperatures have become more frequent. “So many people thought it only happened on exceptional occasions. It took 20 years for a lot of people to raise awareness. So it’s relatively new.”
The same could be said for many places. Climate change has brought unprecedented high temperatures in many corners of the world. But data show that Japan’s temperatures have been rising faster than the global average.1
The rise has been particularly pronounced since 2014, according to the Japan Meteorological Agency. The health consequences have been substantial: deaths from heat stroke more than doubled from 635 in 2017 to 1581 in 2018. The last full year figures, for 2020, were 1528.
In an average year, Japan might have about nine extremely hot days (defined as 35°C and above). But this June Tokyo experienced nine extremely hot days in a row, and a record number of weather observation stations in Japan recorded temperatures over 40°C. It was the country’s worst heatwave since records began.2 According to Japan’s Fire and Disaster Management Agency, over 14 000 people were taken to emergency departments because of heat stroke between 27 June and 3 July.
And while heat stroke understandably gets more attention, this isn’t the main way that heat kills. One study found that across three Japanese cities, higher summer temperatures are linked to increased rates of acute ischaemic heart diseases, cerebral infarction, and pneumonia.3 Though it’s hard to estimate reliably, in Japan excess deaths from heat can reach 10 000 in a hot year, largely linked to cardiovascular and respiratory disease.4
Even before this heatwave, Japan’s Environment Ministry had set a goal of zero deaths from heat stroke, although without a target year. What can the rest of the world learn from Japan’s long battle with extreme heat?
Heat warnings shrugged off Looking forward to people being better informed of the risks of heat to health requires looking back at what failed previously. This often happens reactively after devastating heat waves.5 In Japan, a major turning point was the historic 2018 heatwave. Yet many people remember the heatwave as being less serious than it was and don’t always draw the link to climate change.6 One change that followed was a nationwide heat stroke alert system, launched in 2021. The alert system rests on the wet bulb globe temperature (WBGT), a more sophisticated measure of heat stress than temperature alone.7 Crucially for muggy Japan, WBGT factors in humidity. The alerts are issued on the day before and the day that a WBGT threshold of 33 is expected to be passed. Beyond this, the Japan Meteorological Agency disseminates a monthly outlook and a warm season outlook as early as February. So to a point, it’s possible to prepare for extreme heat. According to the agency, an online nationwide survey of 2000 people conducted in December 2021 showed that 67.2% of people knew about the heat stroke alerts, mostly because alerts are broadcast on television. But that means roughly a third of the population aren’t aware they exist. And Kyoto Prefecture, one place that has been installing WBGT monitors, has acknowledged that its residents do not fully understand WBGT. Knowing that a period of high heat and humidity is on the way is just one part of the puzzle. The more challenging part is getting policy makers, the media, and the general public to take it seriously. The two week warning ahead of the record setting heatwave that started in June 2022 didn’t generate much interest, according to Takafumi Umeda, of the meteorological agency’s climate prediction division. People had to feel the rise in temperatures to begin to be concerned. In general, people can become desensitised to frequent warnings about extreme heat.8 It’s all too easy to ignore recommendations like reducing physical activity. Mandatory limits may need to be set, for instance at public facilities and workplaces, to ensure that the risks aren’t brushed off. This happens in some places in Japan, though inconsistently. Some primary schools keep children indoors during breaks when a heat stroke alert is issued, for instance.
Understanding social norms A larger problem is that some people in Japan see extreme heat as something to be endured, not prevented. A word that comes up often in discussions of Japanese heat is gaman, which refers to dignified perseverance in the face of discomfort. Since 2005, Japan’s “cool biz” programme has encouraged relatively relaxed office attire during the summer, partly as a way to reduce energy consumption. Some offices include signs apologising to visitors for the temporarily slackened dress code of short sleeves and no ties. Still, many people continue to wear multiple layers even in heatwaves. Kanda thinks that gaman is a reason for the underuse of air conditioning by many elderly Japanese people, who may say that they didn’t have or need air conditioning when they were young. Of course, temperatures have risen and older bodies are less able to sense and regulate heat.9 Most Japanese households have air conditioning, yet most people who die indoors from heat stroke in Japanese cities have their air conditioning off at the time (many live alone and also have their windows shut). This may be because of affordability, medical conditions, gaman, or a complicated mix of these factors. Kanda believes that some perceptions need to be updated as heat intensifies. This could involve adjusting hours of work and recreation. For example, it’s traditional to hold certain events at the height of summer temperatures. This includes high school baseball tournaments, where many players get heat stroke. Some will play through heat cramps in their legs. Kazutaka Oka, who researches climate adaptation at Japan’s National Institute for Environmental Studies, believes that behavioural change is possible. When it comes to resistance to using air conditioning, one suggestion he’s heard is for grandchildren to record messages asking grandparents to keep cooling devices on. He believes this could be a good way to convince them.
Managing energy needs Of course, any mention of air conditioning comes with the paradoxical fact that it contributes to climate change yet also protects against its effects. Wakako Sakamoto, the assistant head of the department of environmental safety at Japan’s Environment Ministry, says that the solution can’t be to discourage air conditioning. Compared with climate change, she believes, “heat stroke is an even more urgent life-and-death issue.” The ministry has tried to compromise by calling for energy savings in areas not critical for averting heat stroke. They encourage yearly inspection of air conditioning units to ensure that they are working, as well as cleaning of filters to make them more energy efficient. If people can afford it, Sakamoto says, it’s best to upgrade air conditioning units to the most efficient models. A transition to renewable energy, combined with technological advancement of cooling devices, is critical because this summer, as in China, Japan reached near crisis point with its energy supply. The reserve rate reached a perilously low 3% in the early summer heatwave, and electricity prices rose. One lesson is that energy suppliers need to be able to better anticipate peaks in demand. According to a representative of the energy utility TEPCO, “from next summer onward, studies will be conducted using the estimated demand that reflects the results of this summer, and countermeasures will be prepared.” It’s not yet clear what these will look like. Designing around heat, poverty, and isolation Temperature rise has been especially fast in Japan’s cities, which are densely built and relatively low on greenery.10 Cities have been applying some urban heat island countermeasures,11 including sunlight reflecting pavement and wind paths. But such projects remain largely voluntary, small scale, and up to the discretion of each local government. The 2019 Rugby World Cup and 2020 Olympics gave Kumagaya and Tokyo, respectively, an impetus for investing in heat reducing design, but cities can’t rely on mega-events to make the needed changes. Nor can homeowners rely on incentives to renovate existing buildings for disaster resilience. Subsidies concentrate on new construction, says Toshio Otsuki, an architecture professor at the University of Tokyo. Public spaces are also increasingly important as the nation’s homeless and low income populations continue to age.12 Some of the measures Tokyo’s homeless people use for privacy—like erecting forts made of plastic umbrellas—trap heat on sweltering days. One man The BMJ spoke to, Nagase, said he had been sleeping on the street for over 30 years. In 2021, Nagase developed heat stroke while doing gardening work in 34°C weather. Since then he’s been trying to drink more liquids, and during the day he goes to a library and a park to seek relief from the heat. The problem is what to do at night, when public facilities close. “At night it’s very humid and hot, so I’m just fanning myself,” Nagase says. Social workers say that distributing paper fans helps strike up a conversation with older people during home visits, according to Shinichi Ikegami, of Tokyo’s Ota Ward’s senior welfare department. Conversations like these can help observers to assess home heat conditions and devise plans for safeguarding health during extreme heat—vital for the increasing number of older people who live alone and have little social contact. Still, in Ota Ward only 22.7% of people aged 65 or older are registered for home visits. In general, it’s challenging to reach elderly people living alone, who are at particular risk of fatal heat stroke.
Acknowledgments Additional reporting by Chie Matsumoto. Reporting for this article was supported by the Social Science Research Council and the Japan Foundation Center for Global Partnership, through the Abe Fellowship for Journalists.
Footnotes Competing interests: I have read and understood the BMJ Group policy on declaration of interests and have no interests to declare.
Provenance and peer review: Commissioned; not externally peer reviewed.