Heat waves mess with your brain. Scientists are trying to figure out why.
Heat waves mess with your brain. Scientists are trying to figure out why.
热浪正在扰乱你的大脑，科学家们正试图找出原因。
EXECUTIVE SUMMARY It’s been hot in London this week. Really hot. A dangerous heat wave has hit Western Europe. Yesterday, the UK recorded its highest ever June temperature at 36.1 °C (about 97 °F). But as the weather app on my phone confirmed, it felt like 39 °C. It’s frightening that we are seeing such temperatures in the UK in June. According to the Met Office, the country’s national weather and climate service, June temperatures peaked at an average 19 °C (66 °F) in England between 1991 and 2020.
执行摘要 本周伦敦非常炎热，简直热得离谱。一场危险的热浪席卷了西欧。昨天，英国记录了有史以来最高的六月气温，达到 36.1°C（约 97°F）。但正如我手机上的天气应用程序所显示的那样，体感温度高达 39°C。在英国的六月出现这样的气温令人感到恐惧。据英国国家气象与气候服务机构——英国气象局（Met Office）统计，1991 年至 2020 年间，英格兰六月的平均最高气温仅为 19°C（66°F）。
Across Europe, the heat wave is likely to cause thousands of deaths. There will be other awful consequences for agriculture, infrastructure, and the health system. But this week I want to look at what the heat does to our minds and brains. Personally, I’ve found it almost impossible to think straight. The heat is distracting and my mind is foggy. I dread to think about the conditions of people who work outdoors, in even hotter regions.
在整个欧洲，这场热浪可能会导致数千人死亡。它还将对农业、基础设施和医疗系统造成其他可怕的后果。但本周，我想探讨一下高温对我们的心理和大脑的影响。就我个人而言，我发现自己几乎无法正常思考。高温让人分心，我的大脑一片混沌。我不敢想象那些在更炎热地区户外工作的人们处于什么样的境地。
It’s not just exhaustion and confusion. The effects of heat on the brain can be deadly. And researchers are still trying to figure out why. Studies have confirmed that as temperatures rise, people seem to get more irritable and more violent. Most of these studies are based on associations, though. It’s difficult to directly study how a heat wave might affect our thinking, says Catherine Thompson, a cognitive psychologist at Liverpool Hope University. She has been studying the effects of extreme heat on firefighters instead.
这不仅仅是疲惫和困惑的问题。高温对大脑的影响可能是致命的，而研究人员仍在试图找出原因。研究证实，随着气温升高，人们似乎变得更加易怒和暴力。不过，这些研究大多基于相关性分析。利物浦希望大学（Liverpool Hope University）的认知心理学家凯瑟琳·汤普森（Catherine Thompson）表示，直接研究热浪如何影响我们的思维非常困难。因此，她转而研究极端高温对消防员的影响。
It’s easier to measure people’s cognitive skills before and after they undergo scheduled training that involves entering a burning building. It’s early days, but the team found that firefighters found it harder to focus and control their attention immediately after heat exposure—something people in heat waves can empathize with, I’m sure. The firefighters’ skills returned to normal after 20 minutes or so of cooling down. But they’d experienced just 15 minutes of intense heat exposure.
测量人们在进入燃烧建筑物进行预定训练前后的认知能力要容易得多。虽然研究尚处于早期阶段，但团队发现，消防员在接触高温后，很难立即集中注意力和控制注意力——我相信，经历过热浪的人对此一定感同身受。在冷却约 20 分钟后，消防员的认知能力恢复了正常。但他们仅仅经历了 15 分钟的高温暴露。
Thompson doesn’t know what the effects of living through a days-long heat wave might be—or how long they’ll last. Figuring that out might involve shipping cognitive test kits to thousands of people during the few days’ notice of an impending heat wave. “My guess [is] that no one’s done it because it’s just so difficult to do,” says Thompson.
汤普森不知道经历持续数天的热浪会有什么影响，也不知道这些影响会持续多久。要弄清楚这一点，可能需要在热浪来临前的几天通知期内，向数千人发送认知测试套件。汤普森说：“我的猜测是，没有人这样做过，因为这实在太难了。”
Still, researchers can learn about some of the impacts of heat waves through studies after the fact. And those studies suggest that the heat seems to have more disastrous outcomes for people with mental-health disorders. Those outcomes become apparent when temperatures rise above what is considered typical for a given region. “There seems to be a correlation where the hotter it gets, especially during the hottest times of the year, the worse the mental-health outcomes,” says Joshua Wortzel, who directs the Heat-Mind Lab at Hartford HealthCare in Connecticut.
尽管如此，研究人员仍可以通过事后研究来了解热浪的部分影响。这些研究表明，对于患有心理健康障碍的人来说，高温似乎会带来更灾难性的后果。当气温超过特定地区的典型水平时，这些后果就会变得明显。康涅狄格州哈特福德医疗保健中心（Hartford HealthCare）“热与心理实验室”（Heat-Mind Lab）主任约书亚·沃策尔（Joshua Wortzel）表示：“似乎存在一种相关性，即天气越热，尤其是在一年中最热的时候，心理健康状况就越糟糕。”
In a study published in 2023, Emma Lawrence at the University of Oxford, who studies the effect of climate change on mental health, and her colleagues reviewed the evidence linking mental-health outcomes to ambient outdoor temperatures. They found that during heat waves, there was a 9.7% increase in the rate of hospital admissions for people with such conditions. “People who live with mental-health conditions are among the most susceptible to the physical impacts of heat,” says Lawrence. People with schizophrenia were found to have been three times more likely to die during the record-breaking heat wave that affected Canada in 2021, for example.
在 2023 年发表的一项研究中，牛津大学研究气候变化对心理健康影响的艾玛·劳伦斯（Emma Lawrence）及其同事回顾了将心理健康结果与室外环境温度联系起来的证据。他们发现，在热浪期间，患有此类疾病的人群住院率增加了 9.7%。劳伦斯说：“患有心理健康疾病的人群是对高温带来的生理影响最敏感的群体之一。”例如，研究发现，在 2021 年影响加拿大的破纪录热浪中，精神分裂症患者的死亡率是普通人的三倍。
In order to protect people, we need a better understanding of the mechanisms underlying these effects. After all, a lot of things change when it’s very, very hot. Some people may end up stuck indoors, avoiding outdoor play and exercise, and it can be difficult to get a good night of sleep, for example. Sleep, socializing, and exercise are all really important for our mental health. But whether unusual heat does something specific to our brains is, as Wortzel puts it, “the million-dollar question.”
为了保护人们，我们需要更好地理解这些影响背后的机制。毕竟，当天气非常炎热时，很多事情都会发生变化。例如，有些人可能会被困在室内，避免户外活动和锻炼，而且很难睡个好觉。睡眠、社交和锻炼对我们的心理健康都非常重要。但正如沃策尔所言，异常高温是否会对我们的大脑产生某种特定的影响，这仍然是一个“价值百万美元的问题”。
Research in lab animals suggests that excessive heat can alter the way chemical signals work in our brain. The levels of neurotransmitters like serotonin, for example, seem to increase when rats and mice are exposed to high temperatures, according to multiple studies. The heat may also interfere with the way networks in our brains communicate with each other. It might affect the way oxygen reaches our brain cells. “There are so many biological reasons why brains may be negatively affected by heat,” says Wortzel.
实验室动物研究表明，过热会改变大脑中化学信号的运作方式。多项研究显示，当大鼠和小鼠暴露在高温下时，血清素等神经递质的水平似乎会升高。高温还可能干扰大脑网络之间的通信方式，并可能影响氧气到达脑细胞的途径。沃策尔说：“大脑可能受到高温负面影响的生物学原因实在太多了。”
Emerging research suggests that for whatever reason, children and young people are among the most vulnerable. In research published earlier this week, Wortzel and his colleagues saw a 2.97% increase in the suicide rate among people in the US aged 15 to 24 for every 1 °C increase in average monthly temperature. That’s more than double the increase seen in people over the age of 24 (which is concerning in its own right).
新兴研究表明，无论出于何种原因，儿童和年轻人是最脆弱的群体之一。在本周早些时候发表的一项研究中，沃策尔及其同事发现，美国 15 至 24 岁人群的自杀率随着月平均气温每升高 1°C 而增加 2.97%。这比 24 岁以上人群的增幅高出一倍多（这本身就令人担忧）。
Other work hints that heat exposure might have long-term consequences for children’s brain development. Babies who were exposed to either extreme heat or cold appeared to have altered white matter by the time they were nine to 12 years old—although it’s not clear how these impacts might affect an individual child. “It seems that extreme temperature exposure for very young children may affect their brain development,” says Lawrence, who spoke to me from Oxford. She was meant to be in London for Climate Action Week, but her event, which focused on extreme heat, ended up being canceled … owing to the extreme heat.
其他研究暗示，高温暴露可能对儿童的大脑发育产生长期后果。研究发现，在婴儿时期经历过极端高温或严寒的儿童，在 9 到 12 岁时似乎出现了白质改变——尽管目前尚不清楚这些影响会如何具体作用于个体儿童。从牛津接受我采访的劳伦斯说：“对于幼儿来说，极端温度暴露似乎会影响他们的大脑发育。”她本应前往伦敦参加“气候行动周”，但她那场聚焦极端高温的活动最终却因为极端高温而被取消了。
We are living through the effects of climate change. And that brings a new urgency to the question of how heat affects our brains. Children born in 2020 are predicted to experience around seven times the number of heat waves their grandparents did, says Lawrance. “[We] need to be serious about adapting to a warming world.”
我们正在亲历气候变化带来的影响。这使得“高温如何影响我们的大脑”这一问题变得更加紧迫。劳伦斯表示，预计 2020 年出生的儿童经历的热浪次数将是他们祖父母辈的七倍左右。“我们必须认真对待如何适应一个变暖的世界。”