Sunday, February 17, 2013

Moderate Drinking Isn't Totally Risk-Free? Crap

Let's be honest, it's pretty ridiculous that it's been three decades since anyone bothered to look at an association between alcohol consumption and risk of cancer mortality in the U.S. Surely, even though there was basically no research to point to, few people would be totally surprised to be reminded that maybe there's some other potentially fatal conditions caused by drinking apart from loss of liver function. And certainly, it's foolish to just assume that, as a moderate drinker, you'd expect only the purported benefits without any of these potential consequences. Bringing this discussion back on the table is a good thing, but it's important to do so responsibly and in the proper context.

I can buy that Malort gives you cancer at least (Source)
Earlier this week, researchers published a study aiming to do exactly that. An in-depth article on the research was featured here in the San Francisco Chronicle. The basic idea is that we know alcohol puts people at risk of developing certain types of cancer, including oral, esophageal, liver, and colon cancer, so the study used meta-analyses published since 2000 to calculate the effect alcohol has in developing these types of cancers, controlling for confounding variables. They then used data from health surveys and alcohol sales to estimate adult alcohol consumption, and then analyzed with mortality data from 2009 to estimate how many deaths might specifically be attributed to drinking using formulas established in other countries for similar purposes. This came out to range between 18,000 and 21,000 people, or about 3.5% of all cancer deaths. This is actually higher than the amount of deaths from melanoma, and considering how aware people are of the risks of extended exposure to the sun without sunscreen, risks of drinking alcohol could be unjustifiably underrated. The next step is to establish a dose-response curve, establishing how drinking more might affect this relationship.

Many of the stories on the article focus particularly on the quote that "there is no safe threshold" for alcohol consumption, and that roughly a third of these deaths represented individuals who consumed less than 1.5 drinks per day. Essentially, as many as 7,000 people in the U.S. who drank that amount per day die from cancer each year that they developed because of that consumption. I'm not really interested in poring through the data to question the validity of this number. It's fair to be very skeptical of how granular you can be in determining the risks for each individual based on an average obtained from surveys known to be quite limited, and ecological data like sales. Ultimately, without longitudinal follow-up of drinkers or a case-control study, this represents a fairly low level of evidence on the grand scheme of things. That's not to say to take the general conclusion with a grain of salt. Quite the contrary, actually. It's just that we can't safely interpret exactly how strong (or weak) this effect really is at this point, and need more robust study designs to get there.

Science-minded people like to blame the media for hyping up conclusions of studies, but here you see the investigators explicitly saying that there is no safe amount of drinking. The abstract itself declares alcohol to be a "major contributor to cancer mortality." What message is a journalist supposed to take from that? The headlines are right there, laid out on a platter for them. I don't think that the investigators necessarily egregiously overstated the conclusions, but it wasn't exactly brimming with context. Also, I don't really expect moderate drinkers to really alter their behavior based on this, but it sort of goes without saying that the proper conclusion wouldn't really grab as much attention, and you never know how things will be absorbed. So I'll try and lay one out myself:

Based upon this study, it appears that the the risk of death due to drinking has been underestimated. Even moderate drinking, which has some potential health benefits, may contribute to mortality from one of seven types of cancers largely understood to be associated with alcohol consumption. This is the first look at such an association in the United States in over 30 years, and as such, represents a building block from which to generate research ideas that more effectively establish this association and how different consumption patterns alter its effect.

Now if you'll excuse me, I'm going to the liquor store to buy some rye and a shaker. For real.

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