Science and Technology links (November 28th 2020)

  • Homework favours kids with wealthier and better educated parents. My own kids have access to two parents with a college education, including a father who is publishing mathematically-intensive research papers. Do you think for a minute that it is fair to expect kids who have poorly educated parents to compete on homework assignments? (Not that I help my kids all that much…)
  • Though researchers have reported that animal populations are falling worldwide (presumably because of human beings), this trend is entirely driven by 3% of the animals that are strongly declining while most animals (vertebrates) are not in decline.
  • The expansion of parental leave and child care subsidies has not affected gender inequalities in the workplace. (That is not an argument for abolishing parental leave and child care subsidies.)
  • An hallucinogenic tea can help you grow new brain cells.
  • It appears that aging is partially caused by aging factors found in our blood. In mice, researchers achieved rejuvenation (improved cognition and reduced inflammation) by diluting blood plasma. It confirms earlier work on the topic but shows rejuvenation in the brain. It does not mean that we know how to rejuvenate human beings, but it gives you a new angle of attack that is safe and inexpensive.
  • A paper claims that hyperbaric oxygen therapy brings about rejuvenation in human beings. In effect, it shows a lengthening of the telomeres, this component of our DNA that grows shorter with each division. The lengthening is in some cells only. They also show a reduction of the number of senescent cells: these zombie cells that we tend to accumulate with age. The reduction in senescent cells is only for part of the body and it might be caused by the oxygen (that may kill the senescent cells). It is unclear how this expensive therapy compares with a good exercise regimen. We have reliable markers of biological age based on methylation and they were not used as part of this study.
  • Countries that adopt a flat tax system (as opposed to the more common progressive system) grow richer exponentially faster. That is, though it may seem intuitive that richer people should pay higher percentage of their income in taxes, it may come at a substantial cost with respect to overall wealth.
  • Diabetes is related to a disfunction of the pancreas. Thankfully we can create insuline producing cells, and we can even insert these cells in one’s pancreas. Sadly, they are soon attacked by the immune system and destroyed. It appears that progress is being made, and that viable cells have survived transplantation in the pancreas through a new technique that protects them from the immune system. It works in mice.
  • Cochrane, a credible source when it comes to medical research, published a review of the evidence regarding masks and hand washing with respect to respiratory viral infections:

    There is uncertainty about the effects of face masks. The low‐moderate certainty of the evidence means our confidence in the effect estimate is limited, and that the true effect may be different from the observed estimate of the effect. The pooled results of randomised trials did not show a clear reduction in respiratory viral infection with the use of medical/surgical masks during seasonal influenza. There were no clear differences between the use of medical/surgical masks compared with N95/P2 respirators in healthcare workers when used in routine care to reduce respiratory viral infection. Hand hygiene is likely to modestly reduce the burden of respiratory illness. Harms associated with physical interventions were under‐investigated.

    It does not follow that you should not wear masks or that you should avoid washing your hands. I do and I recommend you do too. However, you should be critical of any statement to the effect that science is telling us that masks and hand washing stop airborne viruses, especially when such statements are made in a political context.

Daniel Lemire, "Science and Technology links (November 28th 2020)," in Daniel Lemire's blog, November 29, 2020.

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Daniel Lemire

A computer science professor at the University of Quebec (TELUQ).

12 thoughts on “Science and Technology links (November 28th 2020)”

  1. Regarding telomeres and hyperbaric oxygen therapy, Daniel says:

    It is unclear how this expensive therapy compares with a good exercise regimen. We have reliable markers of biological age based on methylation and they were not used as part of this study.

    The paper says:

    Several lifestyle interventions including endurance training, diets and supplements targeting cell metabolism and oxidative stress have reported relatively small effects (2-5%) on TL3, [2, 8, 9].

    It sounds like these are different mechanisms. Hyperbaric chambers are expensive but scuba diving is relatively inexpensive and 32% Nitrox tanks/fills have become very common in recreational diving and supported by all modern dive computers. It would be interesting to do the same type of measurements on sport divers, full-time dive masters/instructors (people who dive everyday with customers/students as their job), and even hyperbaric medicine technicians who spend time in the chamber along with their patients.

    Measuring white blood cells for telomere length surprised me. I wonder if inexpensive fingerprick microfluidic devices (like blood glucose monitors) are possible.

  2. I would love to see a flat tax system (one where wealthy people pay as large a percentage of their income as I do). The real comparison is between flat tax and tax systems where wealthy people pay lower taxes.

  3. Regarding mask: This meta-analysis seems to apply mostly to non-pandemic influenza, which is very different from COVID‐19 in many ways. For COVID-19, there are many better studies, also with much larger sample sizes. Picking the first I found, “Mask use during COVID-19: A risk adjusted strategy”, talks about “the meaning of wearing masks has exceeded their direct effects”. The psychological part is very different for influenza.

    In Switzerland, at the beginning of the first wave (March), a right wing politician (Martullo-Blocher), was wearing a mask in the parliament. But she was not allowed, because “it can send a false signal”. Wearing a mask there was only allowed if the person felt sick, but if that’s the case the person should go see a doctor.

    In Switzerland, schools, restaurants, businesses (shops) reopened in summer. Now in the second wave, masks are mandatory in public (indoors, and crowded places). The head of the public health department, Alain Berset, was asked why they were not mandatory in the first wave. He said there were not enough masks, and “What would you say if there are too few life jackets on a boat?” Well, other countries mandated masks in the first wave (e.g. Czech Republic and Slovakia). They went with cloth masks.

    Nowadays, masks are seen as an accepted way to keep (more) businesses open. Of course there are alternatives! Personally, I hold my breath when I pass people, even though I haven’t found any studies that say it helps 🙂

    1. So there is a policy issue and I have advocated masks since the very beginning and was taken aback when governments opposed them. I still advocate wearing mask and I am unlikely to change my stance in the near future.

      The science is something else. I submit to you that the following is not true: “For COVID-19, there are many better studies, also with much larger sample sizes”. We have a single large scale randomized trial, done in Denmark. It was not conclusive. We have a ton of modelling work, but that is not the same.

      The paper you point to is some kind of informal review. It is nothing like what the Cochrane folks do which is an in-depth literature review assessing various important parameters to try to reach out a qualified decision.

      So I think Cochrane is right. We do not know whether masks are useful. And hand washing looks to be only mildly effective.

      Of course, much of the work has been done in viruses other than the one causing COVID-19. But it would be rather extraordinary if the spread of other coronaviruses was not stopped by cloth masks, while the spread of one particular coronavirus was. I think our default position should be that all of these respiratory viral infections have strong commonalities… at least, you should expect strong commonalities among coronaviruses.

      This being said, suppose that masks make only a tiny difference… it might still be worth it wearing them because the spread is so non-linear that you cannot rule out that a small difference could translate into a large difference down the line. (Reducing an exponent by a small amount can eventually make a big difference.)

      And then it is possible that they help a lot but we just have not found a convincing way to establish that. It could take years to do so. Obviously, you do not want to wait years before you act. The precautionary principle is sound in such cases: do something cheap right now in case it might help.

      Furthermore, as you hint, there is a social component to all of this. Some people are scared. Even if masks do not protect them per se, if masks make people feel safer, it is already a win.

      It is unclear whether it has helped keep the businesses open. It seems that masks mandates are correlated with business closures. But I doubt that it is the masks themselves that cause the lockdowns.

      1. I think the the Cochrane review and the Danish study don’t apply for COVID-19:

        The Danish study tested whether masks protect the wearer, not others.
        The Cochrane review contains contains 67 randomised trials. 7 about mask in the community; some in households. It is mainly about influenza, none during COVID-19. Compliance with mask usage was low in many studies. As far as I see, masks were worn after symptoms – but most SARS-CoV-2 infections are spread before/without symptoms.

        The Cochrane review, as well as the Danish study, are also listed in the “Swiss Policy Research” “Are Face Masks Effective? The Evidence.” While I’m Swiss, I have never heard about them. They cherry-pick what they report, see e.g. Wikipedia or

        I think the CDC “Scientific Brief: Community Use of Cloth Masks to Control the Spread of SARS-CoV-2” lists sources that apply better; it doesn’t include the Cochrane review and the Danish study.

        1. I submit to you that part of the argument is fallacious. Given a scientific review that it is referenced by a third party. One may find that this third party is qualified by another third party as being biased… But this tells us exactly nothing about the original source.

          Adolph Hitler could come back from the grave and approve of a document, it would not tell us anything about the truth of the document.

          I know you realize this, but I feel like I need to point it out.

          You criticize the Danish study as being limited. Indeed, it was. But it is the only published randomized control trial we have regarding COVID 19.

          Randomized control trials are the gold standard in medicine, the highest form of evidence we ever get in pratice. Everything else tends to be much weaker.

          The CDC piece you refer to is a policy statement, not a scientific one. The role of the CDC is not to ascertain the truth of the matter. Their job is to protect people. They make a case, as strongly as they can, that cloth masks can help. They refer to observational studies, lab studies and theoretical models. That is, the refer to weak sources of evidence. What they do is that they start with their policy, then they seek to support it by selecting the evidence specifically with the purpose of making their recommendation look credible. For example, the CDC does not review the contrary evidence. They do not include the Cochrane review, they do not include the Danish review. If this was scientific work, they would need to, but they don’t because it is a policy document.

          Personally, I agree with the CDC recommendation. Please wear a mask.

          The Cochrane approach first looks at all available evidence, then weights it by the scientific strength, and then presents it as a whole. They are not trying to make a policy recommendation. They are trying, as objectively as possible, to arrive at the scientific truth. And they conclude that we do not know whether masks work.

          Please let me make this clear: it does not invalidate or goes contrary to the CDC recommendation.

          Here is my expectation… If you asked the authors of the Cochrane study, or the authors of the Danish study, what they think of the CDC recommendation, I suspect that they will say that it is quite fine. They will not object on scientific ground.

          In fact, if you read the Danish study, it is quite clear that they expected to prove that masks work. They have every reason to be disappointed. They would have become instantly famous worldwide had their study gone the other way.

          But they did what good scientists do: they went with what they thought the facts were saying.

          The CDC folks have a different job.

          1. Let me add that the authors of the Cochrane study had also every incentive to have the result come the other way. Their study would have been cited by every government, they would have been invited on multiple news shows.

            Their rather boring conclusion does not advance their careers.

  4. Their rather boring conclusion does not advance their careers.

    Yes, and unfortunately it is used by “Swiss Policy Research” and others to convince that masks don’t help. Looks like it is very hard to proof, using “randomized control trials”, that masks help. So maybe it would be better to not even bother doing that research. Specially because the effect is mainly on “source control”, and how do you do RCT for that.

    But the research was done and published (I do understand that “boring research” is important, and publication bias is a problem). I think it would be better if CDC also referenced them and explained, so that “Swiss Policy Research” and similar have a harder time to mislead people.

    BTW – but I can’t comment on that.

    1. Looks like it is very hard to proof, using “randomized control trials”, that masks help.

      What it looks like, rather, is that people do not take the science very seriously with respect to mask. If they did, there would have been dozens of randomized control trials. There was plenty of opportunity and though such trials are not cheap, there was plenty of funding available.

      To my knowledge, not only was the Danish study the only one, no other is even planned. To understand why that might be, it helps to look at how the Danish researchers were treated. Effectively, if you conduct a serious study and the results do not go in the right direction, your career could be serious harmed. If you believe that there is a good chance that the study would not show mask effectiveness, then your rational decision should be to avoid carrying on with such a study.

      In any case, there was only one and there might be no other (worldwide).

      Yes, and unfortunately it is used by “Swiss Policy Research” and others to convince that masks don’t help.

      Good science can lead to bad policy and bad science to good policy, but that is no excuse to do bad science.

      This being said, this SPR site does seem to reflect our current knowledge…

      Cloth face masks in the general population might be effective, at least in some circumstances, but there is currently little to no evidence supporting this proposition.

      That is the scientifically correct statement at the moment in my opinion. It is speculative that masks may help.

      Note that, as I have explained as clearly as I could, it does not follow that, as a matter of policy, we should not wear masks.

      I can’t comment on that.

      Taleb criticized the statistics of the Danish study. That’s how science is supposed to work. You publish a study, you do your analysis. Other people review it and criticize it. It is the whole process.

  5. This being said, this SPR site does seem to reflect our current knowledge…

    No. All it does is list the sources that say masks may not help or don’t help. This is very similar to the CDC page, however in the other direction.

    1. If you want an objective assessment, then you have to go with Cochrane. They are the gold standard. That is they primary mission and they apply the best standards. The SPR site may not carry a scientifically objective analysis, but it does come to what I believe is the correct conclusion.

  6. Regarding testing the effectiveness of masks, I admit that I haven’t read the studies above. This comment assumes that they were performed in real-world scenarios with volunteers or surveys.

    At some level of detail and thoroughness, could the effectiveness of different types of masks be simulated and researched in a controlled lab experiment?

    Tesing would be performed by both blowing different types of virus (or different, similar-enough materials) at a mask with cough and breathing velocity, and by moving a mask through material in the air at human walking speed.

    Different viruses could be used. Cloth, surgical, kn95, and n95 masks could be simulated or used. A no-mask test could also be used in the coughing and breathing tests. I assume that cloth provides at least some protection, but I imagine that it expands over time, reducing the protection.

    I’m not certain if it’s possible to determine how much virus was stopped by the mask or ended up on the other side of the mask. If there’s not an obvious way, perhaps a ferrous material could be used. I also don’t know how sensitive scales are, but repetition could be used a sufficient amount of times to collect enough material to compare significantly.

    I don’t know anyone who could easily test this.

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