9 ms·

This Study suffers from at least one significant methodological flaw. They did not evaluate the same individuals pre- and post Covid infection but instead evalu

• irthomasthomas 5y ago
  Also those symptoms look very similar to stress, anxiety and depression. Which I think are to be expected after contracting a pandemic level virus and being forced to isolate. I would like to see results after treating or controlling for those conditions.
  • adflux 5y ago
    I agree. I suspect many "long covid" cases are probably not caused by covid, but by the lockdown and psychological impact of this phenomenon. People complaining of fatigue or having difficulty concentrating or having brain fog are in some studies already counted as suffering from long covid. No causual relationship required.
    • CraigJPerry 5y ago
      That suspicion goes against what the people who are dealing with this every day are saying. What makes you suspect this? A friend of mine is a doctor and we were chatting about long covid 2 days ago, his description of it seemed pretty cut and dried to me - e.g. a swimmer here in Glasgow with hopes of getting to the 2024 olympics is currently unable to train due to breathing issues post-covid. They’re supposed to be fully immersed in training right now but can’t since covid in December 2020.
      • murgindrag 5y ago
        One person I know is suffering from serious balance problems post-COVID. It's just not consistent with the "It's all in their minds theory," or "it's the same as stress from isolation" theory. There's clearly something neurological going on, and we don't understand it yet.
        • treeman79 5y ago
          In my case it was a mix of information, increased cranial pressure, and minor clots. Was a nightmare getting those under control but my symptoms eased up. Then I got covid and it all started up again. Took months to get back to a baseline, but symptoms were identical, aside from loss of smell.
      • adflux 5y ago
        Have you read the diagnosis criteria and studies regarding long covid? I have read a few, and I see that many are using the widest net possible to define long covid, counting people who self diagnose symptoms such as brain fog and having trouble concentrating. Ofcourse long covid is real. I am just a bit skeptical about the diagnosis criteria.
        • toss1 5y ago
          That conclusion raises skepticism based on the appearance of motivated reasoning and confirmation bias, but there's insufficient data for a firm conclusion.
        • 5y ago
  • treeman79 5y ago
    I have an autoimmune decease and factor 5. Very similar symptoms as long term covid. Lots of inflammation, brain fog, cognitive defects. I spent years being dismissed as depressed Or having anxiety. When I finally was diagnosed and started treating condition with medications I could handle my cognitive problems and depression lifted. Support groups for autoimmune conditions are full of people who routinely are dismissed by doctors.
    • ImaCake 5y ago
      A few years ago I suffered from an autoimmune issue for about 3 months. It took most of that time just to convince a doctor to give me meloxicam, which is just strong panadol/aspirin really. Having a chronic fever for a few months really made it hard to do anything more substantial than play video games. I don't know how we teach general practitioners, but we are doing something horribly wrong. A lot of long covid people must be finding this out too, and it is just super sad.
      • dmix 5y ago
        A big part is people are typically afraid, or don’t have the opportunity, to get a second opinion. One of my biggest lessons early in life was that not all doctors are the same (by a long shot). This is why it’s so important to see specialists related to your condition. And ultimately you’re going to be most responsible for getting proper care as often only you know what you’re experiencing. Medicine and pathology are far to wide of subjects for generalists to operate efficiently across every field and niche. Which is why specialization is so important and connecting the patients to the right specialists. There’s a lot of analogies to technology, where people tend to expect the experts to do and know everything and completely defer to them. I think we all have experienced this with our parents or people who didn’t grow up with computers. When ultimately the individual is always going to be a huge part of the puzzle and must accept that fact.
      • dTal 5y ago
        >I don't know how we teach general practitioners We send them to a school which emphasizes cramming vast amounts of established knowledge into their heads, at the expense of critical thinking skills, social skills, and for that matter sleep. In a world where doctors use Google and WebMD the same as everyone else (because of course they do, no one retains an encyclopaedic knowledge of every medical condition), it's basically a hazing ritual.
  • IfOnlyYouKnew 5y ago
    If COVID causes stress, anxiety, and depression, why wouldn’t that count as a legitimate effect of the disease?
• DominikPeters 5y ago
  I find it pretty concerning that they don’t mention this issue in their discussion section, which was also the first thing that came to mind when reading the abstract: people who’ve caught COVID may differ significantly from those who didn’t. Did none of the authors nor the reviewers think of this?
  • viraptor 5y ago
    Have you seen "2.4. Statistical methods" and "Table 1" which discuss this? The whole paper is available below the abstract.
    • DominikPeters 5y ago
      Yes, they control for various variables that they know about. I’m not convinced this gets rid of the bias (e.g. they don’t control for working from home, many others). It is not true that they discuss this obvious objection in either 2.4 or Table 1. They only discuss methods they’ve used that very partially mitigate the issue, without mentioning the problem.
      • viraptor 5y ago
        How/why do you think working from home would affect the results of the infected and not infected group? We can throw lots of possible ways to divide the samples of course, but I'd like to understand why you chose that example. (and what's the threshold for "they should've mentioned criteria X")
• glangdale 5y ago
  There's a UK brain imaging study - small, due to the fact that one required the "lucky" confluence of having participated in the study before the COVID-19 epidemic, and having gotten COVID - showing the kind of longitudinal effects you are asking for. Alarmingly, it shows shrinkage of various brain structures even among the mildly ill. Note this is a not-yet-peer-reviewed preprint. https://www.medrxiv.org/content/10.1101/2021.06.11.21258690v2 https://www.medrxiv.org/content/10.1101/2021.06.11.21258690v... IMO, while I'm not inclined to take either study at face value immediately, I think a serious person should be equally reluctant to join the "it's just a flu" camp either.
  • saddlerustle 5y ago
    Apart from the effect size in that study being pretty low, theres the obvious sampling problem in that sort of people regularly having their brain imaged are not normal!
    • glangdale 5y ago
      I'm not clear on what level of "pretty low" I'd have to see before being reassured here. I guess it's HN, where I'm the only dummy who doesn't know what acceptable changes in everyday metrics like "Parahippocampal gyrus thickness" and "Lateral orbitofrontal cortex volume" are. Your second remark is also peculiar: the "obvious sampling problem" to which you allude is either (1) a subtler-than-expected-point about the UK Biobank's program (designed to be a mass participation program to observe longitudinal effects in previous healthy or as yet undiagnosed people) or (2) evidence you are just making stuff up.
    • Aeolun 5y ago
      I dunno, I just have anxiety and the docs only feel safe ruling certain stuff out after either a CT or MRI. If I ever contract COVID I can look back through multiple years of history.
  • yourenotsmart 5y ago
    > I think a serious person should be equally reluctant to join the "it's just a flu" camp either. The long-term effects of flu are not studied that well, by the way. On the basis we're used to it from before such studies were possible. None of those symptoms we hear about, getting our breath, unable to smell, brain fog etc., none of them are new. And they imply internal damage that lasts.
• viraptor 5y ago
  Why do you think adjusting the model for: "Nuisance variables were age, sex, racial-ethnicity, gender, handedness, first language (English vs other), country of residence (UK vs other), education level, vocational status and annual earning." doesn't cover what you ask for here? (including graduate degrees) With the described adjustments and enough data points, the distribution of infection cases shouldn't matter. Or are you making some other point I'm missing?
  • disgruntledphd2 5y ago
    Statistical adjustments at a population level will be much less useful than the pre post design above. Getting estimates from the same people will provide a much lower variance estimaion of any potential effect. Also, adding hospital records to this study would potentially provide a better estimation. All studies have flaws, but this one does look pretty reasonable (the principal components method used should have been better described, for instance, and confidence bounds on the effect sizes would have been super useful).
    • yourenotsmart 5y ago
      The "pre post" is not much of a design, unless we've had a long-term practice to force random healthy people into scanning their brains, or we have a time machine.
      • nradov 5y ago
        There are always medical studies running for other purposes that involve doing brain scans on otherwise healthy people. One of my relatives participated in such a study. Presumably those same subjects could be enrolled in a "pre post" study for COVID-19 effects.
      • disgruntledphd2 5y ago
        Nonetheless, it would be a better design. Horribly impractical, but really useful.
  • nradov 5y ago
• CraigJPerry 5y ago
  >> suffers from at least one significant methodological flaw Is this not a randomised control trial? As I understand it, RCT is usually referred to as the “gold standard” - why would the gold standard be a flaw in this case? What you describe sounds to me, a layman, as an improvement over and above but if RCT is good enough normally, why discount it entirely in this case because there’s some other improvement could be made?
  • nanis 5y ago
    > Is this not a randomised control trial? No. I am not quite sure how one might even think the words apply here. If it were, participants would be randomly assigned to the the "control" group where they do not get Covid, but would be told they had Covid (to control for the negative placebo of being told they are now afflicted with a horrible long term malady) and the "treatment" group which would actually be given a Covid infection. Assuming such a study were doable, one can then use a "within participant" comparison which is much more powerful than comparing statistics across groups. >> We sought to confirm whether there was an association between cross-sectional cognitive performance data from 81,337 participants who between January and December 2020 undertook a clinically validated web-optimized assessment as part of the Great British Intelligence Test, and questionnaire items capturing self-report of suspected and confirmed COVID-19 infection and respiratory symptoms. There is no randomized assignment here. Susceptibility to report a Covid infection without positive proof is a confounding variable. I suspect that susceptibility is correlated with other cognitive issues. A "within participant" comparison as the GP brought up would avoid these kinds of issues.
  • tinus_hn 5y ago
    How can it be a randomized controlled trial? Did they randomize a group from the general population in advance and then randomly and blindly, but in a controlled fashion, infect part of the subjects and did they then consider the effects without looking at whether they were the infected people or the control group, until the conclusion of the study? That’s what’s require for the gold standard.
  • bdauvergne 5y ago
    RCT is not referred as "gold standard" by serious people, https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(15)60742-5/fulltext https://www.thelancet.com/journals/lancet/article/PIIS0140-6... that's marketing.
• agnosticmantis 5y ago
  If about 10% of participants followed up, wouldn’t there be a possibility of non-response/self-selection bias in the pre-post study? If I suffered cognitive deficit, I’d be more/less (I’d think less) likely to follow up.
• derbOac 5y ago
  I agree it's curious they didn't retest individuals at followup, although it's much easier to ask if they contracted COVID than to have them retest. However, they did determine those individuals who contracted COVID were not different in their premorbid test performance from those who did not later contract COVID. This is a big part of what a "complete" longitudinal design would get you. Let's say you did get that test data on follow-up. If post-COVID people who were infected were different cognitively, and not different premorbidly, that would suggest COVID was involved. If they weren't different cognitively, you'd have to explain why the first wave of individuals were different based on COVID history but not the later wave. Still important to show but maybe a different set of explanatory challenges.
• usaar333 5y ago
  They note though that the follow up population that had caught covid after testing didn't differ significantly from those that didn't. That seems to add credibility here to a causal mechanism as opposed to a background correlation of risk of infection they are missing.
• jvanderbot 5y ago
  Wait, what about this: "A common challenge in studies of COVID-19 is that differences between people who have vs. have not been ill could relate to premorbid differences. To address this issue, a linear model was trained on the broader independent GBIT dataset (N = 269,264) to predict general cognitive performance based on age (to the third order), sex, handedness, ethnicity, first language, country of residence, occupational status and earnings. "
  • dash2 5y ago
    That's ridiculously bad. In effect their logic is: "We controlled for various things in the original regression, but hey, there still could be unmeasured confounders that make people who got COVID score less on IQ tests, even before they got COVID! (Like coming from a poorer background, other health vulnerabilities etc. etc. etc.) Unfortunately, we don't have a measure of IQ from before they got COVID. So, we estimated one using a set of variables that we do have measures for!" Erm... if those extra variables predict IQ, then why not just add them as controls? And of course, if you do so, then you'll still hit the problem that there are plenty of potential unmeasured confounders out there. This is just a silly way to pretend you've controlled for something, when in fact you can't. The quality of statistics in medicine is so bad. Disgracefully bad. In particular, the Lancet seems to be a serial offender.
• yosito 5y ago
  Not to mention that many people just aren't smart enough to evaluate risk and understand how to protect themselves in a pandemic. Just today I saw a guy on the metro wearing disposable latex gloves but no mask on the metro. He was obviously concerned about covid but had no concept of how it's transmitted. Some of the other PPE mishaps I've seen would be hilarious of they weren't so sad.