【健康】流感疫苗可能有助于阻止阿尔茨海默氏症 The Flu Vaccine May Help Keep Alzheimer's at Bay

新的研究表明，老年人接种流感疫苗的益处更大。该研究发现，65岁以上的成年人至少接种过一次流感疫苗，在四年后被诊断出患有阿尔茨海默病的可能性明显降低。然而，需要更多的研究来确认因果关系，并弄清楚这种保护作用来自哪里。

阿尔茨海默病是痴呆症最常见的形式，据认为目前影响超过500万美国人。有些生活习惯可以降低一个人患阿尔茨海默氏症的风险，例如定期运动，并且有药物可以帮助控制其症状。但是没有已知的治疗方法可以显着预防或逆转其进展。然而，一些研究指出了某些感染与阿尔茨海默氏症之间的关系，这导致了预防或治疗这些感染可能降低其发病率或延缓其发作的希望。

2020年，休斯顿德克萨斯大学健康科学中心的研究人员分析了医疗记录，发现流感疫苗接种与诊断为阿尔茨海默氏症的相关风险较低之间存在联系。这一次，他们转向了一个更大的医疗索赔数据库，并能够比较美国近一百万对65岁以上的成年人的结果，他们要么接种了流感疫苗，要么没有接种疫苗。这些配对在年龄等因素上是匹配的，平均跟踪了46个月。

在研究期间，8.5%的未接种疫苗的成年人被诊断患有阿尔茨海默氏症或接受经常用于管理的药物，而接种疫苗的个体为5.1%， 相对风险降低约40%。似乎还存在累积效应，使得在研究期间每年接种疫苗的人患阿尔茨海默氏症的可能性最小。研究结果于本月在线发表在《阿尔茨海默病杂志》上。

近年来的研究表明，某些细菌可以在生命早期感染后隐藏在大脑中，并直接引发阿尔茨海默氏症的发展，特别是疱疹病毒。但作者推测，这项研究中看到的联系并不一定是流感独有的。相反，它更多的是关于我们的免疫系统和衰老大脑之间的关系。

“由于有证据表明几种疫苗可以预防阿尔茨海默病，我们认为这不是流感疫苗的特定效果，”研究作者Paul Schulz说，他是UT麦戈文医学院神经认知障碍中心主任， 在一份声明中说。“相反，我们认为免疫系统是复杂的，一些改变，如肺炎，可能会以一种使阿尔茨海默病恶化的方式激活它。但激活免疫系统的其他事情可能以不同的方式做到这一点 - 一种保护阿尔茨海默病的方式。

这些观察性研究只能证明两件事之间的相关性，不能清楚地证明疫苗接种与阿尔茨海默氏症风险之间的因果关系。但其他研究团队也发现了类似的联系。当然，针对流感和其他疾病的疫苗仍然有效，可以有效地预防其目标细菌的严重疾病 - 这些好处对老年人来说往往更为明显。

需要时间来弄清楚为什么疫苗可能有助于保持我们的大脑保持良好状态，但它们已经为我们做了很多好事。就研究人员而言，他们接下来可能会计划研究covid-19疫苗是否可以对痴呆症提供类似的缓冲作用。

New research suggests even more benefits for flu vaccination in older people. The study found that adults over 65 who received at least one flu shot were noticeably less likely to be diagnosed with Alzheimer’s disease up to four years later. More research will be needed to confirm a cause-and-effect link and to figure out where this protective effect is coming from, however.

Alzheimer’s disease is the most common form of dementia, and is thought to currently affect more than 5 million Americans. There are lifestyle habits that may reduce a person’s risk of Alzheimer’s, such as regular exercise, and there are medications that can help manage its symptoms. But there are no treatments known to substantially prevent or reverse its progression. However, some research has pointed to a relationship between certain infections and Alzheimer’s, which has led to hopes that preventing or treating these infections may lower its incidence or delay its onset.

In 2020, researchers at the University of Texas Health Science Center at Houston analyzed medical records and found a link between flu vaccination and a lower associated risk of diagnosed Alzheimer’s. This time, they turned to an even larger database of medical claims and were able to compare the outcomes of nearly a million pairs of adults over 65 throughout the U.S. who were either vaccinated or unvaccinated for the flu. The pairs were matched in factors like age and were tracked for an average of 46 months.

During the study period, 8.5% of unvaccinated adults were diagnosed with Alzheimer’s or received medication often used to manage it, compared to 5.1% of vaccinated individuals—about a 40% lower relative risk. There also appeared to be a cumulative effect, such that people who consistently got vaccinated annually during the study period were the least likely to develop Alzheimer’s. The findings were published online this month in the Journal of Alzheimer’s Disease.

Studies in recent years have suggested that certain germs can hide in the brain following infection earlier on in life and directly trigger the development of Alzheimer’s, particularly herpesviruses. But the authors speculate that the connection seen in this study isn’t necessarily unique to influenza. Rather, it’s more about the relationship between our immune system and the aging brain.

“Since there is evidence that several vaccines may protect from Alzheimer’s disease, we are thinking that it isn’t a specific effect of the flu vaccine,” said study author Paul Schulz, director of the Neurocognitive Disorders Center at UT’s McGovern Medical School, in a statement. “Instead, we believe that the immune system is complex, and some alterations, such as pneumonia, may activate it in a way that makes Alzheimer’s disease worse. But other things that activate the immune system may do so in a different way—one that protects from Alzheimer’s disease.”

These kinds of observational studies can only demonstrate a correlation between two things, not clearly prove a cause-and-effect link between vaccination and Alzheimer’s risk. But other research teams have found a similar connection. And of course, vaccines for the flu and other diseases remain effective at preventing severe illness from the germs they target—benefits that tend to be even more pronounced for older people.

It will take time to figure out exactly why vaccines may help keep our brain in good shape, but they’re doing plenty of good for us already. The researchers, for their part, may next plan to study whether covid-19 vaccines can offer a similar buffering effect against dementia.

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