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george davey smith Profile picture
@mendel_random
Oct 1, 2020 • 5 tweets • 2 min read • Read on X
Covid cases are lowest in places that at the peak had the fewest or the most covid deaths. @dannydorling Tony Brookes and I considered reasons for this

theconversation.com/why-are-corona… Image
1/n The pattern could be a chance quirk, or could reflect testing regimens being related to previous severity of the epidemic, or safer behavioural patterns in areas badly affected, or more homeworking being possible in such places (or a mix of the above)
2/n 2/n It could be that enough people in such areas have already come into contact with the virus that the population is now less susceptible to the disease. Overall, this would imply that the levels of some forms of immunity in those particular neighbourhoods are higher
3/n at a level that leads to a detetable reduction in the number of new cases.. Such immunity will not be all or none – making people completely unsusceptible to SARS-CoV-2 infection – rather they would require more sustained, higher viral load exposure to become infected,
4/n or, if infected, show less symptoms and be less likely to be tested. Note this is not an all-or-none phenomena as is sometimes suggested by discussions of population immunity - will send additional short thread on this later

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More from @mendel_random

george davey smith Profile picture
Apr 23
1/n In 2019 @BMJ_latest published a non-linear Mendelian randomization (NLMR) paper with the conclusion that gaining weight would reduce mortality risk in many people. The NLMR method produces spurious findings MR's credibility calamity in this 🧵 bmj.com/content/364/bm…

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2/n The sad story of NLMR and the delays in journals and authors in issuing retractions of clearly spurious papers containing damaging public health messages that include *literally impossible* findings is told here /cont
3/n this contains a quiz you can try at this stage
Read 4 tweets
george davey smith Profile picture
Mar 11
Just seen that @ucl have made Lyndsay Farrall's 1969 PhD "The origins and growth on the English Eugenics movement" easily found with new intro by @profjoecain It remains perhaps the best overview of the topic, and deflates some myths. The survey of /contucl.ac.uk/sts/sites/sts/…
2/n the well-known members of the "Eugenics Education Society" and a random sample show academics and medical doctors the most common professions, that leftists as well as conservatives well represented, that Lamarckian eugenics was a thing (so much for the bizarre notion /cont
3/4 that transgenerational epigenetics in its soft inheritance form is somehow more progressive than genetics), that biometricians were as common as Mendelians amongst the early eugenicists. Essentially the desire to stop the working class reproducing was ahead of racism /cont
Read 4 tweets
george davey smith Profile picture
Jan 18
A brilliant 1984 chapter in the "Encyclopaedia of Medical Ignorance" by Richard Peto anticipated much of the advances in understanding of cancer since then, and is now accessible in @SpringerNature European Journal of Epidemiology. A personal🧵on it/ cont link.springer.com/article/10.100…
1/n I first read this sitting on a stool in the HK Lewis medical bookshop on Gower Street soon after it came out; the book was outside my budget & the rest not so interesting. It felt like the 19th century in Lewis' anachronistic shop, there were hardly any customers /cont Image
@Lyonpaul @mrc_ieu @SpringerNature @The_MRC 2/n no one seemed to buy anything and the rumour was it was a front for an MI5 office. I was left alone reading away, and was entranced by the sparkling language but must admit I understood hardly any of it. I recalled it when reprinting another Richard Peto chapter in/cont
Read 9 tweets
george davey smith Profile picture
Dec 11, 2023
A twee story on tea by @TorstenBell in @guardian suggests increased consumption of tea (using boiled water) led to a fall in mortality in Britain. This might be true, but there is no mention of how this was linked to massively increased deaths in India 🧵
theguardian.com/commentisfree/…
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1/n The academic paper @guardain story is based on suggests that growing tea consumption by the working class after 1784 in Britain led to a fall in mortality. It uses what it calls "The Tea and Windows Act of 1784" which led to a dramatic fall /cont repec.iza.org/dp15016.pdf
@guardain 2/n in taxation on tea. There was no such act, though the 1784 Commutation act did decrease tax on tea from over 100% to 12.5%, and tea imports went up. Why was this act introduced? It was introduced on the behest of Richard Twinning - of Twinning's tea that some vanity /cont
Read 10 tweets
george davey smith Profile picture
Dec 1, 2023
In 2018 we published a non-linear Mendelian randomisation (NLMR) study in @ObesitySociety and it is now clear the method we applied is deeply flawed, so in October we published a Perspective correcting it. A 🧵on the cautionary tale of NLMR onlinelibrary.wiley.com/doi/epdf/10.10…
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2/n Naïve observational studies report J- or U- shaped upturns of mortality at lower levels of BMI. Our paper using UK Biobank (UKB; @uk_biobank) data suggested overall adverse effects of BMI on mortality, and (though very imprecisely estimated) the NLMR suggested a lower /cont
@uk_biobank 3/n BMI below which an upturn in mortality was seen than was seen in the observational analysis /cont onlinelibrary.wiley.com/doi/epdf/10.10…
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Read 12 tweets
george davey smith Profile picture
Nov 3, 2023
Ultra-processed foods (UPFs) are apparently the new poison, and a recent @bmj_latest report by @rebeccacoombes suggests conflicts of interests in the “expert” views presented @smc_london that weren’t enthusiastic enough in promoting this notion. /contbmj.com/content/383/bm…
2/n Opposing these @DoctorChrisVT says there is “overwhelming evidence” of UPFs being harmful. The prospective studies (contrary to the quote, these were not “trials”, where people were randomised to higher or lower UPF consumption) do not show UPFs cause harm / cont Image
@DoctorChrisVT 3/n Their use is strongly patterned by socioeconomic position, health behaviours and other factors that would generate non-causal associations in such studies. Nor does the fact the studies were done @imperialcollege or adjust for some covariates. An equally large body / cont
Read 8 tweets

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