生物与医学2020sciencedirect.com
维生素 D 改善 Covid-19 老年患者的生存率
Vitamin D improves survival in Covid-19 elderly patients
入门 · 约 30 分钟读完前置知识：观察性研究方法、混杂因素概念
导读
这篇论文通过一家养老院的自然观察数据分析维生素 D 补充与新冠老年患者生存率的关系：66 名感染老人中，57 人在确诊前后接受过规律维生素 D 补充，与未按时补充的 9 人相比生存率更高。作者据此认为维生素 D 补充可能改善老年新冠患者的预后，但该研究并非随机对照试验。
HN 关注点：疫情期间 HN 读者高度关注维生素 D 是否真能降低新冠死亡率，讨论焦点集中在这项非随机研究的证据强度以及'低成本低风险是否值得推广'的决策权衡。
HN 评论精选
这几条评论里：质疑 1 补充 3
质疑从研究设计角度系统质疑：样本极小、对照组成因不明、多重比较，属于弱证据
这里的讨论似乎都在泛泛而谈维生素 D，而忽略了研究本身。在我看来，这项研究是弱证据。它不是随机对照试验，而是对一次'自然实验'的历史分析——这本身没问题，但我不认为这算得上真正的'实验'。据我理解，这家养老院共 96 名住户都接受常规维生素 D 补充，其中 66 人感染新冠。研究者发现其中 57 人在确诊前一个月内或确诊一周内接受过补充，这构成'干预组'，剩下 9 人是'对照组'，结果干预组生存率更高。我认为证据薄弱有三个原因：对照组人数极少（只有 9 人！）；论文似乎没有解释这些人为何没有按时补充，因此很可能存在混杂因素；此外研究同时考察了皮质类固醇、羟氯喹、抗生素和维生素 D 四种干预——尝试的因素越多，其中某一项出现相关性就越不奇怪。
scott_s查看英文原文
The current discussion here seems to be about Vitamin D in general, and ignoring the study itself. In my reading, this study is weak evidence. This was not a randomized, controlled trial, but historical analyses of a natural experiment. In itself, that's not a problem: we can learn a lot from natural experiments. But I don't think this instance is much of an "experiment." As I understand it, all of the residents (96 in total) of a particular nursing home receive regular Vitamin D supplementation. Of the total residents, 66 got COVID-19. Among that group, they realized that 57 of them had received their Vitamin D supplementation either within a week of being diagnosed with COVID-19, or one month prior. That is the intervention group. The remaining 9 people are the "comparator" group. They found the intervention group had better survivability. The main three reasons I consider this study weak evidence is that the number of people in the "comparator" group is very small (9!), and they - as far as I can tell - do not explain why these people did not receive their normal Vitamin D supplementation. The "comparator" group is supposed to have had a similar baseline, but there's still, to me, a strong possibility of a confounding factor. Finally, there were four total interventions: corticosteroids, hydroxychloroquine, "dedicated antibiotics" and the observation about Vitamin D. The more things you try, the less surprising it should be that there is a correlation along one of them.
补充即使证据不强，低成本低风险下推广补充剂也是合理的公共卫生决策
维生素 D 的关键在于：制造成本低、风险已知且很低。即使没有对照研究，我们也有理由相信它可能有助于对抗新冠，尤其是对缺乏者。把它免费提供给并推荐给所有摄入不足的人是合理的策略——相关性也许不是因果，但代价极小，可能仍然值得。对戴口罩也可以提出几乎相同的论证。
Jabbles查看英文原文
The important factors for Vitamin D are that it's cheap to manufacture and has well known (low) risks. We have reasons to believe that it might help fight Covid, especially in deficient individuals, even if we do not have controlled studies. Making it freely available and recommended for anyone who doesn't obviously get enough already is a reasonable strategy. It might not work - the correlation may not be causal. But it might be worth it anyway, because the downsides are minimal. You could make roughly the same argument for wearing masks.
补充提问：冬季日照不足是否是新冠冬季严重程度飙升的原因之一
向更懂行的人请教：冬季日照减少（以及其他因素）在多大程度上导致了寒冷季节病情严重程度的激增？我知道还有其他因素：室内空气循环流通、湿度等。
gdubs查看英文原文
People who know more about this than I do: how much do we think the lack of sunlight in the winter (among other factors) contributes to the severity spikes associated with the cold season? I know the other factors: recirculated indoor air, humidity, etc.
补充补充实用信息：D3 服用时间影响睡眠，且应搭配 K2 以避免钙过量
友情提醒：维生素 D3 如果在一天较晚的时间服用可能影响睡眠，我如果中午前忘了吃就会直接跳过。另外，D3 不搭配 K2 一起补充可能导致钙过量。
woj-tek查看英文原文
Friendly reminder: vitamin D3 can affect sleep if taken later in a day. I tend to skip if I forget to take it before noon. Also, D3 without additional K2 may lead to calcium excess.
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