Tuesday, November 24, 2009

Drinking your way to....health? oblivion? cancer? More on 'evidence based' medicine

Perhaps the main concern of our blog is to understand biological causation. Our interests are general, but the issue comes up disproportionately in understanding the findings of medical research, because that is naturally what a large fraction of funding supports.

Well, last week the BBC reported a study in Spain that says that men's health is substantially improved by moderate daily drinking (sorry, women, maybe your turn will come with the next discovery). That is, 3 or so drinks a day reduces heart disease risk by 35 to even 50 percent-- a very substantial difference indeed!

But why did this story make the news? How many times does alcohol consumption have to be studied in regard to health risks? It is included in many, perhaps the vast majority of epidemiological studies, and it has been so for many decades. How could such an effect have been missed? Indeed, how could it possibly be that we don't have solid, irrefutable knowledge by this time? Why would even a Euro cent have to be spent to study its effects any further?

This is highly relevant to the notion of 'evidence based' medicine, because the recommendation about alcohol use bounces around like silly putty. The only thing that is uniformly agreed on is that too much is, well, too much (but the greatest heart disease risk reduction includes those Spanish guys downing 11+ drinks a day).

Here is a case in which culture is part of the nature of 'evidence'. In prudish America, alcohol is considered something so pleasurable as to be necessarily a sin and is studied intensely. It has been controversial whether hospitals should offer patients a dinner glass of wine. Officials dread to recommend drinking at all. So the 'evidence' required to make a recommendation depends on subjective value judgments. But even if one were to be a hard-nosed empiricist, we again ask how we could possibly not know the answers with indisputable rigor.

If this is the nature of evidence, then what evidence do we accept? Is it always the latest study? Why do we think that is any better than the next latest study to come down the pike tomorrow? And if so, why don't we ignore today's study? Why do we think former studies were wrong (some may be identifiably so, but most aren't obviously flawed). Is some aggregate set of studies to be believed? Is it the study that let's business as usual be carried on, for whatever reason?

Our answer is that in addition to the cultural side-issues, there are so many complex factors at play, both causal in regard to what alcohol does in the body and what the body does to it, and in regard to confounding factors, that there is no simple 'truth' and hence it is unclear what counts as 'evidence.' Confounders are factors that may not be known or measured but that are highly correlated with the measured variable of interest (daily alcohol consumption) so that cause itself is hard to identify.Confounders may be causal on their own, or may causally interact with the factor under study.

For example, if the more you drink the more you smoke or the less sleep you get, or the more sex you enjoy (which, since pleasurable, is a sin and must be harmful) these other factors, rather than the alcohol, could be what affect your heart disease risk directly.

Confounders are confoundedly difficult to identify or tease out. Their exposure patterns and even their identity can change with lifestyle changes. And then there are many potentially directly relevant variables, too. When do you drink? What do you drink? With or without olives or a twist of lemon (or salt on the rim)? How uniform is your daily consumption whose average is measured on a survey? Even if these things were known, the future exposure patterns cannot be known, so that today's evidence is really about yesterday's exposures and so the accuracy of future risks based on this evidence is inherently unknowable.

Finally, if drinking is encouraged and heart disease is reduced, will this be good for public health? Or will it increase the number of, say, fatal accidents or violent crimes? Or is it -- well, it is -- a kind of Get-Cancer program? Why? Because if you don't get heart disease you'll live longer and that by itself increases your cancer risk. Not to mention the risk of Alzheimer's, hearing and vision problems, and a host of other older-age problems.

Perhaps the oldest advice in western medical history is from Hippocrates, about 400 BCE. That was "moderation in all things." In today's world, with our romantic notions about the powers of science, such advice is so non-specific and non-technical, that it is considered a cop-out that is not 'evidence-based'. Maybe so, but it's still the best advice. That's because it implicitly includes the unmeasured and unpredictable risk-factor regimes to which people are exposed--and that is evidence.

"Just the facts" sounds like raw empiricism, the kind of rational empiricism our society values. But the 'facts' weave a tangled web.


Holly Dunsworth said...

Do you think people really want to know more and more detailed answers and that's what drives us to keep searching beyond what we already know, or do you think we are motivated by money, hope of fame, and the need to occupy our time? Or is it something else?

In one of my classes students have come to realize that "we will probably never know" the answer to Questions A, B and C, Infinity. Basically to all the questions raised in popular biological anthropology topics that they are researching. I asked my students yesterday, after a discussion of first human occupation of the Americas that ended in "we don't know much and we'll probably never know", I asked them, "what do we already know about it?" And they could say QUITE A LOT. So what's the problem? Why does it seem like we don't know much about the first Americans or much about anything?

I think it's partially because there are curious and driven people out there searching for more and that MAKES IT SEEM like what we already know is somehow insignificant.

In the case of alcohol helping hearts. Um, duh? Open hearts and broken hearts: These are the people you find at a bar.

Ken Weiss said...

We know a tremendous amount, and science has led the way in many areas (not, as far as I can see, in the area of broken or lonely hearts, unfortunately).

It's not good for the research business to stress what we know. It only pays to stress what we don't know.

Often we teach things as if we know them much better than we do, and then act surprised when the next discovery is touted as revoutionary.

Things might be better if we taught what we know in more measured terms, and didn't try to make what we don't know seem to trivialize what we do know.

Maybe scientific questions are never totally answered because as we gain knowledge the question, like a mirage, continually moves into the distance.

Like for some people who are never satisfied, the search for Mr or Ms Right?

Holly Dunsworth said...

Love it, Ken. Love. It.

Ken Weiss said...

A blunt question would be: how much would we lose if we were prevented from doing any more research on, say, the functional anatomy of primate locomotion or dentition, or the phylogeny of spiders?

The answer is: not much. There are no burning questions, really. We would still be able to teach students to enrich their knowledge of the world in important ways.

But in areas like understanding consciousness, or autism, probably we'd lose a lot.

Holly Dunsworth said...

"no burning questions, really"? Hmph. It's all relative! ;)

Ken Weiss said...

Well, if you're going to say that everything we don't know constitutes a 'burning question' then everything really isn't relative, it's absolute--absolutely burning.

I didn't say 'no questions' remain, no even no interesting questions. But I personally think we have to have some way to set priorities of relative importance in a limited world. Including what and how we teach. So yes, things are relative.

To a primate anatomist, every detail of locomotor anatomy may be vitally interesting. To a diabetologist, it's of zero importance.

If everything is of equal importance, then it's like advertising where every product is new! the best! revolutionary!

In that case, what gets studied or, in practical terms, what studies get funding, will be based even more strictly that it is now upon insider trading (old boy networking), lobbying, and social politics rather than even an attempt to set priorities.

Some would argue that's better since priority setting is essentially politics and judgment anyway. Others would say value for dollar in some societal sense, like reduced disease, or some more fundamental-knowledge sense (e.g., as may be the case in regard to consciousness).

But you are right that it is all relative, at least relative to each person's personal worldview. Some would argue that it's worth it to smoke happily for 50 years, taking millions of satisfying puffs, and that having to put up with only a few miserable weeks dying of lung cancer is easily worth it.

Holly Dunsworth said...

Just to be clear, that was a winking emoticon in my comment, which means that it should be read with a playful tone coming out of a playful face.

Holly Dunsworth said...

I mean, you used primate locomotion and dentition as an example, so I had to say SOMETHING in response to that, this being a public forum, and me being a tribal organism and all. ;)

Ken Weiss said...

Aaah! Anne always accuses me of being too literal! I didn't realize that in using locomotion to challenge my post, that you were just, um, pulling my leg.

Anne Buchanan said...