I saw this tweet from a doctor, Vinay Prasad, where (in a long Twitter thread) he debates the merits of that big Lancet study which said having more than 5-7 drinks a week could be harmful. I follow Dr. Prasad and generally like what he says:
I thought he made some good points (e.g. concordance between epi studies and randomized control trials (RCTs) and, of course, confounding) but I wasn’t dissuaded because:
1. The study withstood peer-review in a prestigious journal. The Lancet has a good reputation, a high impact factor (“the relative importance of a journal within its field; journals with higher impact factors are often deemed to be more important than those with lower ones”)
In the 2014 Journal Citation Reports, The Lancet was ranked second among general medical journals, (with an impact factor of 45), after The New England Journal of Medicine (impact factor of 56).
2. It was a big study (data from nearly 600,000 people). It was international (studies from 19 high-income countries). It had close to 120 co-authors. All of these, to me, improve the credibility of the findings.
3. If the study has problems or is “flawed” (all studies are “flawed”) why not request a formal retraction? Or write a letter to the editor? Or contact the corresponding author with your concerns? I’m not being sarcastic; he seems to have the stock to do this. Why instead go on Twitter and call it “bullshit”? I’m wary of criticisms that degrade into this language.
4. He complains about confounding and publication bias. Good points. But authors of all studies contend with these. There is no pure study. I do like this that he said about confounding:
Confounding, meaning that the people who drink >100g/wk are different than those who drink less, and these differences, not the alcohol drive the outcome.
5. He criticizes epidemiological (epi) studies as a group. But they are useful when, for instance, you can’t ethically perform a trial. Are we to have people consume 10, 20, 30 drinks a week – for years – and compare their disease outcomes to a randomly selected control group that drinks no alcohol? It reminds me of when we gave people syphilis and followed them to record what happened. That was the Tuskegee experiment, one of the last studies of its kind because it was horribly racist and unethical. Ethics is why we don’t conduct a randomly controlled trial on smoking; we’re not going to give people cigarettes to see if they get lung cancer. … Also RCTs have their own problems. They aren’t broadly generalizable, and they too suffer publication and research bias.
6. In the end, he says:
“We may have to make decisions the same way we decide how often to go to the bathroom or movies, i.e. using common sense.”
Common sense. That should be our guide? Forget science? So … How much alcohol should we drink? Use common sense. Never mind that it is subjective and means different things to different people. How many cigarettes should we smoke? How much saturated fat should we eat? How much salt, sugar, coffee, soda pop, trans fat, donuts, burgers, fries, pizza, cookies, bacon, milkshakes? Common sense. (I don’t agree with this.)
There is an element of sexism here in that women who drink alcohol, any amount, increase their risk for breast cancer; men do not.
He didn’t dissuade me about this study. I do not think it is bullshit. There is a biologically plausible mechanism for alcohol’s link to disease. It is an IARC Group 1 carcinogen. It damages tissues. Public health workers should warn consumers about alcohol’s risks and not just tell them to use common sense. Going to the bathroom or the movies will not give you cancer.