https://www.bbc.com/future/article/20230724-can-slow-breathing-guard-against-alzheimers

人们相信缓慢、刻意的呼吸有很多好处。研究人员可能发现这种呼吸的另一个好处——对阿尔茨海默氏症有让人吃惊的防护作用。

停止玩手机。现在慢慢吸气，集中精力扩张肺部，数到五。呼气，缓慢而刻意地呼气，数到五。

你可能会发现，就在那 10 秒钟内，你突然感觉稍微放松或注意力集中了一点。每周几次，每次 20 分钟，进行同样的练习；研究表明，你可能不仅仅获得感觉平静的好处；你还可以帮助自己预防各种疾病的发生， 甚至包括阿尔茨海默病。

呼吸练习（breathing exercises），有时称为“做呼吸（breathwork）”；其好处已得到 几千年的认可。近几十年来， 科学研究 似乎支持许多地区的人们，特别是 在亚洲，长期以来一直在实践的：有意识的呼吸可能有助于 改善多种健康状况，包括高血压、压力、焦虑、 甚至慢性疼痛。

在最新的研究中，研究人员测量了血浆中与罹患阿尔茨海默氏症较高风险相关的生物标志物，特别是淀粉样蛋白 40 和 42。 108 名参与者中，有一半被告知要尝试通过想象宁静的场景、聆听轻松的声音并闭上眼睛来让自己平静下来——本质上就是正念冥想。目标是减少他们的心率波动，鼓励他们的心率更稳定、更一致。

另一组则在电脑屏幕上进行呼吸练习——当方块在五秒内上升时，他们吸气；当方块下降五秒时，他们呼气。研究发现，这种深而缓慢的呼吸可以 增加心率波动 – 使心跳之间的时间间隔更加可变（因此“心率变异性”更高）。两组患者每天练习两次，每次20 ～ 40 分钟，持续五周。

南加州大学老年学、心理学和生物医学工程教授、该研究的作者之一玛拉·马瑟 (Mara Mather) 表示，当参加者在练习四个星期后，查看他们的血液样本时，结果“令人惊讶”。旨在增加心率变异性的呼吸练习降低了β淀粉样蛋白的水平。正念练习使得β淀粉样蛋白的水平更高，因为它降低心率变异性。（The breathing exercises aimed at increasing heart rate variability decreased levels of amyloid beta. The mindfulness exercises, which decreased heart rate variability, made those levels higher.）【译者问：作者是说正念练习有可能导致老年痴呆？】

尽管尚未确定导致阿尔茨海默氏症的明确单一原因，但已发现称为斑块的淀粉样β蛋白团块是 该病的主要特征之一。当这种蛋白质的某些类型在脑细胞内聚集在一起时，它们的毒性特别大，会造成脑细胞损伤，影响其正常功能并导致它们死亡。

马瑟和她的团队没有预料到β淀粉样蛋白的水平会“受到如此强烈的影响”。这不仅适用于老年人，他们可能已经更容易受到更高水平的β淀粉样蛋白的影响。 “这种影响对于年轻人和老年人来说都很显着，”马瑟说。

“这是一个有趣的发现，因为在健康成年人中，血浆β-淀粉样蛋白水平较低与以后患阿尔茨海默病的风险较低有关，”她说。 “慢节奏的呼吸可能不仅有利于情绪健康，而且有利于改善与阿尔茨海默病相关的生物标志物。”

研究人员不确定这到底是为什么。但一个假设是，缓慢、有意识的呼吸可能会模仿深度睡眠的一些好处，研究发现，这可能会带来一些好处。 清除神经毒性废物 以更快的速度从大脑和神经系统中释放出来。这些废物的积累似乎在阿尔茨海默氏症的发展中发挥了作用。

关键因素似乎是每次运动如何影响心率变异性（HRV），它反映了心跳之间的波动程度。 研究表明 心率变异性是衡量神经系统功能的良好指标，因此是整体健康状况和各种健康状况（从抑郁和慢性压力到病毒感染和败血症）的指标。有趣的是， 更多的 变异性（即不太一致的模式）似乎更健康，也许是因为它显示了身体适应压力源的能力。

马瑟说，无论具体机制如何，有规律的、有意识的、慢节奏的呼吸似乎对大多数人都有好处。

“我们还不知道最佳剂量是多少。但可能不必每天都进行——我目前的猜测是每周 4～5 次、每次 20 分钟会有好处，”她说。

该研究没有比较不同类型的呼吸方式，因此他们还不知道哪种类型的呼吸模式可能最有效。马瑟说：“我们所知道的是，以每次呼吸 9 ～ 14 秒之间的任何速度进行呼吸，可以最大程度地增加个人的心率波动，从而有效降低血浆淀粉样蛋白水平。”

该研究还需要在更多的患者中进行重复才能证实 是否可以看到有意义的长期效果。一些科学家对呼吸方式是否比药物治疗更加有效或可靠表示怀疑。

但这并不是近年来唯一发现呼吸练习对健康有益的研究。例如，研究发现，呼吸可以降低高血压患者的血压，有助于缓解焦虑和抑郁症状，并减少失眠。与此同时，最近的一项荟萃分析发现，它可以减轻压力并改善心理健康。

呼吸练习开始超越瑜伽和冥想课程，进入企业静修甚至学校。在纽约市，市长埃里克·亚当斯（Eric Adams）最近宣布，所有公立学校都必须向学生教授每日正念呼吸课程。正如他所说：“呼吸是一门科学。”事实证明，有很多研究人员开始同意他的观点。

Can slow breathing guard against Alzheimer's? 

https://www.bbc.com/future/article/20230724-can-slow-breathing-guard-against-alzheimers

There are believed to be many benefits to slow, controlled breathing. Researchers may have found another – a surprising protection against Alzheimer's.

Stop scrolling. Now inhale slowly, concentrating on expanding your lungs, to a count of five. Exhale, just as slowly and deliberately, as you count to five.

You might find that, in just that 10 seconds, you suddenly feel just a little bit more relaxed or centred. Follow the same practice for 20 minutes a few times a week and – according to the research – you might not just reap the benefits of feeling calmer. You may also be helping to prevent the onset of various diseases, including, a recent study has suggested, even Alzheimer's disease.

The benefits of breathing exercises – sometimes called "breathwork" – have been recognised for millennia. In more recent decades, scientific studies seem to support what people in many cultures, particularly in Asia, have long practiced: that deliberate breathing may help to improve a variety of health conditions, including hypertension, stress, anxiety, and even chronic pain.

In the latest study, researchers measured biomarkers in blood plasma that are associated with a higher risk of developing Alzheimer's, particularly amyloid beta 40 and 42. Half of the 108 participants were told to try to bring themselves to a place of calm by imagining a serene scene, listening to relaxing sounds, and closing their eyes – essentially, mindfulness meditation. The goal was to decrease their heart rate oscillations, encouraging their heart rate to have a steadier, more consistent beat.

The other group followed a breathing exercise on a computer screen – when a square rose over the course of five seconds, they inhaled, and when it dropped for five seconds, they exhaled. This kind of deep, slow breathing has been found to increase heart rate oscillations – making the time interval between heart beats more variable (hence a higher "heart rate variability"). Both groups practiced the technique twice a day, for 20 to 40 minutes each time, for five weeks.

When they looked at participants' blood samples four weeks into their practice, the results came as a "surprise", says Mara Mather, professor of gerontology, psychology and biomedical engineering  at the University of Southern California and one of authors of the study. The breathing exercises aimed at increasing heart rate variability decreased levels of amyloid beta. The mindfulness exercises, which decreased heart rate variability, made those levels higher.

Although no definitive single cause has been identified for causing Alzheimer's, clumps of amyloid beta protein known as plaques have been found to be one of key features of the disease. Certain types of this protein can be particularly toxic when they clump together inside brain cells, causing them damage that affects their normal function and causes them to die.

Mather and her team hadn't expected the levels of amyloid beta to be "affected so robustly". And it wasn't just for older adults who already might have been more susceptible to having higher levels of amyloid beta. "The effects were significant in both younger and older adults," Mather says.

"This is an intriguing finding because, in healthy adults, lower plasma levels of amyloid beta are associated with lower risk of getting Alzheimer’s disease later," she says. "Slow-paced breathing might have benefits not only for emotional well-being – but also for improving biomarkers associated with Alzheimer’s disease."

The researchers aren't sure why, exactly, this might be. But one hypothesis is that slow, deliberate breathing may mimic some of the benefits of deep sleep, which research has found might clear neurotoxic waste products from the brain and nervous system at a faster rate. The build-up of these waste products seems to play a role in the development of Alzheimer's.

The key factor seems to be how each exercise affected heart rate variability (HRV), which reflects how much fluctuation there is between heartbeats. Research has indicated that heart rate variability is a good metric for the functioning of the nervous system, and, therefore, an indicator of overall health and various health conditions, from depression and chronic stress to viral infection and sepsis. Intriguingly, more variability (ie a less consistent pattern) seems to be far healthier, perhaps because it shows the body's ability to adapt to stressors.

Regardless of the exact mechanism, Mather says, a regular practice of deliberate, slow-paced breathing seems to be something that could benefit most people.

"We don't yet know what dose is optimal. But it probably doesn't have to be every day – my guess at this point is that doing 20 minutes 4-5 times per week would have benefits," she says.

The study didn't compare different types of breathing techniques, so they don't know yet which type of breathing pattern might be most effective. "What we do know is that breathing at whichever pace between nine and 14 seconds per breath that increased that individual's heart rate oscillations the most was effective at reducing plasma amyloid beta levels," Mather says.

The research has also yet to be replicated in larger numbers of patients to confirm whether a meaningful long-term effect can be seen. Some scientists have also expressed doubts about how effective or reliable breathing techniques could be compared to drug treatments.

But it is far from the only study in recent years to have found health benefits of breathing exercises. Studies have found, for example, that breathwork may reduce blood pressure in people with hypertension, help relieve symptoms of anxiety and depression, and reduce insomnia. A recent meta-analysis, meanwhile, found that it could lower stress and improve mental health.

Breathwork is starting to make its way beyond yoga and meditation classes to corporate retreats and even schools. In New York City, mayor Eric Adams recently announced that all public schools will have to teach daily mindful breathing sessions to students. As he put it: "There's a science to breathing." There are plenty of researchers, it turns out, starting to agree with him.