Sunday, August 29, 2021

How to read medical statistics correctly?

The Bright Light News website claims to be "Shining a light on the Covid-19 narrative. Investigate. Facts matter." An article on the website dated August 23, based on statistics from the British government, is titled "More Fully Vaccinated Dying of Delta Variant Than Unvaccinated". This conclusion is surprising, and on the surface of it, is difficult to explain. I checked the original data of the British government website (see the small print after Source for the URL), and found that the Bright Light article quoted the data correctly (see Table 5 on pp.22-23): In the survey, 57.1% of the people who died of the Delta variant of the coronavirus in England were completely vaccinated, and 32.8% of those have not been vaccinated. So where is the problem?

The reality is that the vast majority of the people in the UK, about 90%, are fully vaccinated. Therefore, the ratios 57.1% and 32.8% cannot be compared in isolation. If the former were 90% and the latter 10%, i.e. matching the ratios of the vaccinated and unvaccinated population, and if there is no other factor that confounds the matter, we would be able to conclude that vaccination does not increase or decrease death rate; if the former were to exceed 90%, the latter less than 10%, then it would be that vaccination will increase the chance of dying. In case this is not clear enough, let's see another example. Imagine you have 1000 apples, 900 of them being red and 100 green. If there are a total of 10 apples that have gone rotten, 9 of them red and 1 green, and suppose there are no other confounding variables related to rotting of apples (e.g., some apples are kept in the refrigerator and others are not), then we can say that the color of the apple is unrelated to whether it rots, but we cannot say "Look! Red apples are more likely to rot than green apples, in fact by 9 times more likely!" If 6 out of 10 rotten apples are red and 4 green, we can't say that the color of the apple is unrelated to whether it's going bad or not. On the contrary, we should say that red ones are less likely to go bad, even though 6 is greater than 4!

Medical students must receive formal training in epidemiology. I have read such a textbook, in which there're plenty of such logical questions. But the case above is much simpler than the exercises in this type of textbook, and no special training is required to draw correct conclusions. Sadly, the website that claims "Shining a light" is lacking in basic logical thinking and misleads gullible people into vaccination rejection.

Saturday, March 6, 2021

Choline helps reduce Alzheimer's risk for certain people: a new study

The following is a bullet-point summary of a recently published research. Specifically, this is a layman's summary of a medical news article, "APOE4 Alzheimer’s Risk Could Be Abated by Common Dietary Supplement", published on ClinicalOMICS magazine, supplemented with other information such as that on Wikipedia.

  • The primary authors of the published research article work for MIT.
  • People carry APOE (Apolipoprotein E) genes, which are involved in the metabolism of fats. The APOE2 variant is good, 3 neutral, 4 bad in terms of risks for late onset Alzheimer, as well as cardiovascular diseases. 14% of the general population, but almost half of Alzheimer's patients, have APOE4. Most people have APOE3.
  • The Wikipedia page for choline states that "[s]tudies observing the effect between higher choline intake and cognition have been conducted in human adults, with contradictory results". And WebMD article says "Insufficient Evidence for ... Alzheimer disease". But the authors of this new study said "those trials were not targeted specifically to people with the APOE4 gene".
  • "[C]holine supplementation ameliorated the APOE4-induced lipid defects... [M]ost people don’t consume that much [of recommended choline]... [P]eople who carry the APOE4 gene may benefit from taking choline supplements... The APOE4 carriers are more susceptible to choline deficiency."
  • According to Wikipedia, beef liver contains the most choline per unit weight, 418.22 mg/100g, followed by chicken liver (290.03 mg/100g), hen egg (251.00), "wheat germ, toasted" (152.8), bacon (124.89), soy bean (115.87), pork loin (102.76). Vegetables are not rich sources of choline; the highest are brussels sprout (40.61) and broccoli (40.06), followed by cauliflower (39.10).
  • Choline is not considered vitamin. Multivitamins you may be taking do not contain choline. Severe deficiency, which is unlikely, "causes muscle damage and non-alcoholic fatty liver disease" according to Wikipedia.

Thursday, July 16, 2020

African/African-American and Non-Finnish European populations more susceptible to COVID-19

According to New insights into genetic susceptibility of COVID-19: an ACE2 and TMPRSS2 polymorphism analysis published on 15 July 2020 in BMC Medicine by Cleveland Clinic researchers,

"the distribution of deleterious variants in ACE2 differs among 9 populations in gnomAD (v3). Specifically, 39% (24/61) and 54% (33/61) of deleterious variants in ACE2 occur in African/African-American (AFR) and Non-Finnish European (EUR) populations, respectively (Fig. 1b). Prevalence of deleterious variants among Latino/Admixed American (AMR), East Asian (EAS), Finnish (FIN), and South Asian (SAS) populations is 2–10%, while Amish (AMI) and Ashkenazi Jewish (ASJ) populations do not appear to carry such variants in ACE2 coding regions"

If needed, Figure 1b can be viewed here. This research of course mean Latinos or Asians can take it easy when it comes to prevention. In fact, the outbreaks in Brazil and India appear to contradict this research. But this research is about genetic susceptibility, not considering the social factors that may play a greater role, such as whether people wear face masks and keep social distancing.

Thursday, July 9, 2020

Advice against COVID-19, "wash hands" vs. "wear masks", in the past months

If you recall the advice from CDC and WHO since early 2020, you may notice that they strongly advised washing hands in the first few months, and did not emphasize wearing face masks as much, let alone social distancing. This is unfortunate misguidance to the public in view of the fact that the new coronavirus SARS-CoV-2 is air-borne and transmits more through people's breath and less through touching.[note1] I wish the experts at these organizations had emphasized wearing face masks and keeping social distance more than or at least as much as washing hands early on.

Anyway, to confirm my impression that the ratio of advice on wearing masks to hand washing increased in the past few months, I took advantage of Microsoft search engine Bing's historical searches.[note2] First I search on for "wash hands" (no quotation marks used) while limiting the time range to 1/1/2020 - 1/31/2020, 2/1/2020 - 2/29/2020, ..., 6/1/2020 - 6/30/2020. I record the approximate search result counts given by Bing. Then I search for "wear masks" and record the same counts. The result is in the following.

  wash hands  wear masks
1    524,000     362,000
2    643,000     557,000
3  2,220,000   1,640,000
4  2,090,000   3,620,000
5  2,490,000   5,350,000
6  2,270,000   4,860,000

The left column is the month, January (1) through June (6). The right column is the search result count for the month. We can tell that "wash hands" was found on much more webpages in March than February as if Americans woke up to the grim reality in March. So was "wear masks". But "wash hands" more or less reached a plateau, while "wear masks" overtook "wash hands" in April and stays in the lead ever since.

This comparison by no means is a direct proof of CDC or WHO's failure to advise the more efficient preventive measure, because the Bing-indexed webpages are authored by all sorts of people. But the public listens to these health authorities. If they say more about "wash hands" and less about "wear masks" and "social distancing", people do it, too.

By the way, the latest Economist magazine has an article Face-off over face-masks: Europe’s latest north-south split, which shows that more and more people in 14 countries started to wear face masks over time. It's interesting to see that Asian countries generally have a sharper rise of the curve than those in Americas and Europe, apparently reflecting the Asian tradition of collective compliance. (The reason China appears to be high all the time is that the data didn't start till February, when COVID-19 was already spread in China.)

[note1] Not that touching contaminated surfaces is less risky. But the probability of touching such surfaces and bringing the viruses into the body is lower than directly receiving air-borne viruses in an environment where at least one person is virus carrier or spreader.
[note2] Google also provides historical search results. But in these searches, the estimated result counts are not given.

Friday, April 24, 2020

Racial distribution of COVID-19 cases in New York

According to New York City data, age-adjusted rates of COVID-19 cases per 1000000 people as of April 16,2020 are

Race EthnicityNon-hospitalizedNon-fatal hospitalizedKnown to have died
Black/African American335.5271.792.3
combined with NYC demographics
White: 63.79%
Black or African American: 15.64%
Other race: 8.76%
Asian: 8.31%
Two or more races: 3.05%
Native American: 0.41%
Native Hawaiian or Pacific Islander: 0.04%

We can see that African Americans are disproportionately represented as many media outlets or government organizations acknowledged. But less known is that the Asian population is significantly represented as well, if we factor in the proportion of the Asians in the whole population in the city. Note that White is 63.79% in the population compared to Asian 8.31%. This is 7.67 times as much. But the non-hospitalized cases are 190.4 and 95.1, for White and Asians respectively. Note 190.4/95.1=2.00. This means in NYC, Asians are 7.67/2.00=3.83 times as likely to contract the virus (but not hospitalized) as the white. Similar calculations can be done to non-fatal hospitalized cases and deaths.