Posts

Seasonality of COVID-19, Other Coronaviruses, and Influenza 2020-04-30T21:43:19.522Z
The Puzzling Linearity of COVID-19 2020-04-24T14:09:58.855Z
Body Mass and Risk from COVID-19 and Influenza 2020-04-07T18:18:24.610Z

Comments

Comment by radford-neal-1 on Desperately looking for the right person to discuss an alignment related idea with. (and some general thoughts for others with similar problems) · 2020-10-24T01:33:04.182Z · LW · GW

I think you should share it with one other person.  Almost any other person, as long as you have reason to think they are knowledgeable enough to understand it, and that they will take you seriously enough to listen to the idea.  Since you're talking about a (small) chance of billions of deaths, they don't have to be ethical paragons - a very high fraction of people will not want that to happen, even if they're otherwise rather awful people.  

This person will then be in a position to give you more useful advice, starting with whether or not your worries are at all rational.  (If they're not, and are instead a sign of illness, then I guess it would be good if the person was not too unkind...)

Comment by radford-neal-1 on The Puzzling Linearity of COVID-19 · 2020-07-02T01:36:56.274Z · LW · GW

Thanks! Very interesting.

Comment by radford-neal-1 on Second Wave Covid Deaths? · 2020-07-01T23:41:23.980Z · LW · GW

Another possibility is better disease survival due to increased vitamin D levels from sunshine (or due to some other physiological effect of sunlight).

The effect seems rather large for this to be the explanation, but it sure would be great if a bit of sunlight is all that's needed!

Comment by radford-neal-1 on Atemporal Ethical Obligations · 2020-06-27T15:40:43.036Z · LW · GW

Indeed. And one can come up with other lists that stem from somewhat different moral intuitions, like:

  • Forcing children (even against the wishes of their parents) to spend much of their day being indoctrinated in whatever ideology is dominant in university departments of education.
  • Confining prisoners (many not guilty of anything that should be a crime) in conditions where it is guaranteed that they will be victims of multiple criminal acts.
  • Confiscating about half the wealth produced by people, for the benefit of politically favoured insiders, or to be distributed to subsets of the population in order to buy political support.
  • Subverting freedom of speech by heavily regulating use of first the radio spectrum, and then when technology changed, wired electronic communications, continuing with this even when such media become the dominant form of communication.
  • Preventing sick people from taking whatever drugs they think have the best chance of saving their life.

So one can see that there are plenty of things currently supported by large numbers of people that are plausibly in the "worse than Hitler" category, without even getting into possible future denigration of the colour green.

And of course the opposite of all the above might also be plausibly condemned by some future society:

  • Allowing children to be misled by their parents' incorrect views.
  • Letting too many bad people run free when they ought to be in prison, and not some wishy-washy "nice" prison, of course.
  • Letting rich (>$40000/year) people spend their money on whatever stupid thing they want, rather than on things that are socially useful.
  • Letting people express harmful opinions.
  • Letting sick people take drugs that don't work, or if they do "work", do so only by saving their life but leaving them weakened, and a burden on society.

There's really no substitute for making your own moral judgements. The idea that the future will always be more moral than the past seems quite false. Even if there is some slow, long-term moral progress (which I think may be the case), there are obviously significant regressions over the time scale of decades and centuries. Going by what you think (correctly) will be the moral views 20 years in the future would not be a good thing in the Germany of 1920.

Comment by radford-neal-1 on Covid-19: My Current Model · 2020-06-05T14:24:30.813Z · LW · GW

From the abstract: "The incidence of new illness compatible with Covid-19 did not differ significantly between participants receiving hydroxychloroquine (49 of 414 [11.8%]) and those receiving placebo (58 of 407 [14.3%])"

So the treatment group did have a lower incidence of illness than the control group, but the difference wasn't statistically significant. However, only 107 patients in total became ill. This is a rather small sample, so the results by no means rule out a clinically important benefit of HCQ. Even just taking the observed proportions as a best estimate, there's a 17% reduction of illness in the treatment group, which doesn't seem negligible, and the actual benefit could plausibly be considerably larger. (Of course, given the small sample size, it's also plausible that the real effect is in the other direction.)

Comment by radford-neal-1 on The Puzzling Linearity of COVID-19 · 2020-05-13T16:21:12.987Z · LW · GW

That seems like a plausible explanation. I wonder how one could confirm it? If there were two sets of covid death counts based on strict and on loose criteria, one could see if there is a divergence in their rates of increase.

Your comment didn't show up at my blog. Not sure why...

Comment by radford-neal-1 on Covid-19: Comorbidity · 2020-05-11T14:21:25.190Z · LW · GW

I looked at covid and BMI in a post linked here. Using data from UK critical care units, it seems that BMI from 30-40 is only a small risk, though the risk from BMI>40 is substantial. This is after adjusting for age and sex.

A more recent UK study here found increased risk of death, after adjusting for age and sex, for obesity (BMI>30), and a substantially higher risk for BMI>40. These risks went down a bit when also adjusting for other factors. (Though depending on your purpose, this may not be valid, since some of these factors might be on the causal path from obesity to risk of death.)

You're saying that obesity matters mostly if you're younger than 60, which is a question not directly addressed by these results (which come up with a single risk ratio, on the assumption that it's the same for all ages). The study here which you link to gives a scatterplot of BMI versus age in covid patients, showing a negative correlation. This is not meaningful information without a corresponding scatterplot for the general population from which these patients came, which they oddly do not show (or even speculate about, if data is hard to find). In that scatterplot, patients with really extreme obesity (BMI>50) seem to play a large role.

In my post, I present evidence that low BMI may be a risk factor, perhaps not only for BMI below the official "underweight" threshold of BMI<18.5 but also for around BMI<20. Frustratingly, many studies do not present the data that would allow one to investigate this. For the recent UK study I linked above, they use "not obese" as their reference class, grouping everyone with BMI<30 together, though their raw, unadjusted, data indicates that there is a substantial firsk for BMI<18.5 (and even in that data, they group everyone with BMI from 18.5 to 24.9 together, even though past studies show that there may be substantial differences within this supposedly "normal" range).

When looking at varying effects by age, one possibility to consider is that high BMI is a risk factor for younger people, and that low BMI is a risk factor for older people (as opposed to BMI not mattering for older people, as you sort of conclude).

Comment by radford-neal-1 on Fast Takeoff in Biological Intelligence · 2020-04-26T14:04:59.086Z · LW · GW

No, I wasn't thinking of modification of adult somatic genes. I was thinking of reproductive maturity taking 12 years, which you're right is also about how long it takes to reach adult levels of cognition (though not knowledge, obviously). The coincidence here leads to the ambiguity in what you said. Actually, I doubt this is a coincidence - it makes biological sense for these two to go together. Neither would be immutable if you're making profound changes to the genome, although if anything, it might be necessary to prolong the period of immaturity in order to get higher intelligence.

Comment by radford-neal-1 on The Puzzling Linearity of COVID-19 · 2020-04-25T22:29:49.404Z · LW · GW

Those are both good points.

It does seem likely that the measures that have been taken do a lot more to inhibit between-household transmission than within-household transmission, so there could be a lag while within-household transmission works itself out before an exponential decline in new cases/deaths becomes evident.

And if there's a testing backlog, and deaths are only recorded as COVID-19 deaths once a sample is finally tested, that would also introduce a lag. This seems like it must vary a lot with locale, though...

Comment by radford-neal-1 on Fast Takeoff in Biological Intelligence · 2020-04-25T21:39:41.639Z · LW · GW

I'm not following the logic here. I presume that "fast takeoff" is supposed to mean that someone with increased intelligence from the first improvement is then able to think of a second improvement that would have been beyond what earlier people could have thought of, and so forth for additional improvements. The relevant time interval here is from birth to thinking better than the previous generation, which need have nothing to do with the interval from birth to reproductive maturity (an interval which is not immutable anyway). The person who thinks of the new improvement doesn't have to be one of those who gestate the next generation.

Comment by radford-neal-1 on The Puzzling Linearity of COVID-19 · 2020-04-25T15:16:38.604Z · LW · GW

I could see that as the explanation if the curve has stopped going up exponentially because we are approaching herd immunity, but that isn't what's commonly believed... Instead, we'd expect the number of new deaths each day to have shifted to a different exponential curve as a result of control measures, and only by coincidence would this exponential have a coefficient near zero (hence nearly constant deaths).

[Though as Vaniver points out, it's a bit more complicated when you account for the serial interval (the time lag for an infected person to infect another).]

Comment by radford-neal-1 on The Puzzling Linearity of COVID-19 · 2020-04-25T02:19:39.055Z · LW · GW

Thanks for the interesting graphs!

Rt=0.85 with serial interval of 6-8 does look almost like a straight line for the relevant time period. Given that the actual data is noisy (probably beyond simple Poisson variation, with various reporting effects), it may be compatible with that explanation (without, for instance, needing to hypothesize stranger reporting artifacts that would systematically keep the reported deaths nearly constant). Though the linear plots of world case and death counts at https://www.worldometers.info/coronavirus/ do still look very straight to me.

As a more general point, it's not entirely satisfactory to say that you made an observation and got Rt approximately one, so that's just what it is. The simple model would be that initially R0 was something greater than one (otherwise we'd never have heard of this virus) as a result of viral characteristics, human behaviour, weather, etc. - it could be 1.3, could be 4.7, etc. - and then we changed our behaviour, and so Rt became something smaller than R0 - maybe a lot smaller, maybe a little smaller, hard to tell. There's no reason in this model that it should end up really close to one, except by chance. If it seems to be really close to one, then alternative models become more plausible - such as a model in which testing or hospital limits somehow lead to reported cases or deaths saturating at some upper limit (regardless of the real numbers), or in which the transmission mechanism is something completely different from what we think - since in these models there may be a good reason why the apparent Rt should be close to one.

Comment by radford-neal-1 on The Puzzling Linearity of COVID-19 · 2020-04-24T20:00:29.274Z · LW · GW

I discuss that possibility in the post. It seems more plausible as an explanation for linear growth in confirmed COVID-19 cases than for linear growth in deaths attributed to COVID-19. For the latter, the situation would have to be something like... there's no tendency to use tests on the most serious cases (many of whom die), and instead they test a fixed number chosen at random of those who come to medical attention (of whom the most serious are a small, fixed fraction), and only attribute a death to COVID-19 if it was of someone who tested positive.

Comment by radford-neal-1 on The Puzzling Linearity of COVID-19 · 2020-04-24T18:02:50.095Z · LW · GW

Yes, an R0 (or maybe Rt is the term to use) of one would give linear growth. But why should it be close to one in so many countries? (I think 0.85 isn't close enough.) There seems to be no reason for the effect of the interventions that have been made to hit one this closely, other than shear coincidence.

One of the arguments I've heard against "flattening the curve" is that to keep infections below health care capacity you have to get Rt so close to one that you might as well do a bit more and get it well below one. (And anyway you'd have to aim for that to be sure that it doesn't stay well above one.) It's hard to believe that we'd hit one so precisely when nobody knows what the effect of the interventions really is.

Comment by radford-neal-1 on Body Mass and Risk from COVID-19 and Influenza · 2020-04-08T13:31:52.062Z · LW · GW

I certainly agree that BMI is not ideal, but that's what we've got as far as most presently-available studies go.

In addition to all the problems that you mention with BMI, there is just systematic measurement error, which is seldom mentioned. Is the height measured with or without shoes? Do unhealthy people tend to slump rather than stand up straight, reducing their measured height, or does the person measuring height make sure to get them to stand up straight? Is weight with or without clothing? What time of day is weight measured (the morning, right after a big meal,...)? I think different answers to these questions could shift measured BMI by about 0.5, perhaps systematically for different studies. Of course, this would affect ABSI too, along with whatever similar problems there are for measuring waist circumference.

Thanks for the link to the paper on ABSI. It looks very interesting. From a first glance, it seems to support the view that the WHO "normal" category for BMI extends too far in the low direction. (Of course, using ABSI as well rather than just BMI might give better information.)

If one has measurements on height, weight, and waist circumference, and a reasonable number of subjects, I think one would actually want to look at all three measurements, not just a one or two dimensional condensation of them, using some suitably flexible model for the relationship with mortality.

Comment by radford-neal-1 on April Coronavirus Open Thread · 2020-04-07T18:19:07.663Z · LW · GW

Thanks for the suggestion. I've put it up as a post now.

Comment by radford-neal-1 on April Coronavirus Open Thread · 2020-04-07T17:32:05.507Z · LW · GW

I've written a blog post on "Body Mass and Risk from COVID-19 and Influenza", available at https://radfordneal.wordpress.com/2020/04/06/body-mass-and-risk-from-covid-19-and-influenza/

Here's the intro:

Understanding the factors affecting whether someone infected with COVID-19 will become seriously ill is important for treatment of patients, for forecasting and planning, and — with factors that can be changed — for personal decisions aimed at reducing risk. Despite our current focus, influenza also remains a serious disease, so understanding its risk factors is also important.

Here, I’ll look at some of the evidence on how body mass — formalized as Body Mass Index (BMI, weight in kilograms divided by squared height in metres) — influences prognosis for respiratory diseases. Information specific to COVID-19 is still scant, but there is more data on influenza and on other respiratory infections (which includes coronaviruses other than COVID-19). Information on how BMI relates to general mortality should also be helpful.

Below, I’ll look at two relevant papers, plus a preliminary report on COVID-19. To preview my conclusions, it seems that being underweight and being seriously obese are both risk factors for serious respiratory illness. Furthermore, it seems that “underweight” should include the lower part of the “normal weight” category as defined by the WHO. Official advice in this respect seems dangerously misleading.