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Epidemiology

October 27, 2010 Leave a comment

Gary Taubes, in an article for the New York Times Magazine[0], talks about the science of epidemiology. He starts off by discussing horomone replacement therapy for women. The idea behind HRT was to ‘cure’ aging. In hindsight, it seems obvious that doing so is futile, especially given the harmful effects that we have more recently discovered. Taubes seems to think that there’s some sort of problem with the initial medical recommendations towards HRT, since we (clearly) didn’t fully understand the effects at the time and probably don’t now, but his bigger problem is that women were advised to continue taking HRT after menopause. He says that this is because of how new scientific discoveries are announced: when the media hears about some new medical discovery, despite a lack of review, they push it right out to the public as medical advice. Physicians then proceed to recommend the new treatment, the FDA doesn’t stop them because in this case HRT was already thought of as a good idea, and it was just being used differently. When more people took it doctors started to realize that it caused certain side effects, so then no one took it, until a paper was published saying that the benefits outweigh the risks – something that is true in most of medicine: when ER doctors need an emergency blood transfusion and don’t know the patient’s blood type, they go for O negative: the benefits of getting blood quickly outweigh the chance of wasting some more universal blood, when doctors have a patient in immediate danger, they medicate rather than bothering to ask the patient about potential allergies, because the benefits of saving the patient outweigh the rather slim risk of allergy, and an allergic reaction can be treated if it occurs. Even medications like Tylenol have a certain risk – but it is such a good painkiller that we use it, even the effective dose is so near to the toxic dose. These are considered acceptable risks, and rightly so, by modern medicine, so the current state of the medical opinion of HRT is at least internally consistent, however the author’s complaint is rather with the changing state of medical consensus: the classic “you were wrong before, how can we know you’re right now”. I think we’ve discussed this in the past in this class, so we’ll move on.

The author goes on to discuss the merits of preventative medicine. He makes the point of observational studies vs. controlled experiments, and how an observational conclusion can very quickly be spun into medical fact, and it’s not until the conclusion of a controlled experiment that we learn that there is no correlation. This explains the flip from a potentially good treatment back to a treatment with no positive gain with the discovery that the previously observed correlation is not a sign of any actual causation. Epidemiologists who seek to find similar links between behaviors or treatments and undesired side effects. He goes on to complain that these controlled experiments are rarely performed because they are rarely funded and lists a few cases where they were unsuccessfully. I have a few problems with that.

For one, no one is making Mr. Taubes take every supplement and perform every practice which is correlated with better health. The fact is that even strong correlations can exist between better health and slightly detrimental practices, if those practices are thought to be healthy, due to a combination of the ‘health-nut’ population and the chronically unhealthy population. The health-nuts might follow some extreme number of practices thought to be healthy, and might have a lower risk of heart disease, which the unhealthy population will be the opposite. If a study looks only at a specific remedy and ignores other factors, such as perhaps healthy eating, then the positive benefits of healthy eating may overshadow a negative effect of the remedy in question, leading to an incorrect result. Researchers can try to fix this using probabilities and things, but it is rather difficult to assign a numerical value to how healthy someone eats, and even less so to expect a large population of an observational study to do so consistently. This sounds like a support of his point, but it really isn’t: my point is that it is perhaps better to let the observational researchers do their studies, as they give actual researchers some useful leads, and just ignore the output of their observational studies. You’re allowed to do that, you know, just not take the health advice you find from some observational study, just like you don’t necessarily look at the health practices of your friends and try to emulate them. While it might feel good and cathartic to write a nine-page article in the Times Magazine condemning observational studies, it’s really not necessary. And statistically speaking, it is better, at least marginally, to take medical advice from observational researchers than from whatever anecdotal advice we get from friends, although most people tend to base their lives on the latter.

Also, it’s worth arguing that what he is talking about is not the entirety of the field of epidemiology. Epidemiology is not solely based around preventative medicine, it also does seek to analyse the causes and spread of disease, which is something it does quite well. See, I think most doctors would agree that epidemiology is merely statistical and cannot provide any actual proof, merely indicate certain probabilities of correlation and of causation. And when you’re in the middle of an epidemic – what the field is actually named for – epidemiologists are pretty good at determining its source and estimating its spread.[1] They do it every year to determine the optimal vaccination for flu, to name a single instance. Epidemiology was the field that gave us our very first understanding of disease, and it did pretty well: epidemiologists said stay away from the sick people, and that worked pretty well.

Another pretty good success case for epidemiology is certain dietary laws in religion. Many kosher laws fit this category: meat is only considered acceptable if it comes from a certain list of animals, was slaughtered in a particular way (by a qualified person, perhaps preventing people from slaughtering animals on their own if they are unqualified to determine its safety, perhaps also promoting certain cleanliness), although fish are generally permissible (many jewish communities were and are located on the water, so people were able to fish on their own, rather than relying on buying food or waiting for deliveries, and are also generally fully consumed in a single meal; these ensure freshness). The same is true of halal, which applies to Islam: both forbid pork (and so do the Scottish) and frown upon blood or carrion, they limit slaughter of animals to some specific process which ensures some measure of cleanliness and control and forbid eating of animals found dead. Some Catholics don’t eat meat on Fridays, perhaps because near the end of the week the deliveries of food are beginning to age and become less safe – fish is permitted again because it tended to be acquired locally, and dairy was forbidden unless you served in the Crusades. I’m not entirely clear on how that last one ties in with epidemiology.

Statistically speaking, the theory behind epidemiology as preventative medicine is also sound, but there are too many problems for it to be practical. Studies are all too often plagued by selection bias (people concerned about their health are more likely to participate, or more likely to engage in more ‘healthy’ behaviors, causing a bias) or subjectivity (rate your pain on a scale of one to five) or other biases in response (people claiming to exercise daily, except for the three days a week they missed, or to eat healthily, because it’s the more acceptable thing to do).[2][3]

It’s important to keep two distinctions in mind: epidemiology has a few fields, including preventative, which covers public health, like the diet and heart disease examples. There is also an aspect of analyzing an epidemic after it exists, such as its first use against diseases like cholera – here the strength of using a statistical rather than scientific approach is apparent, as it isn’t necessary to fully understand the mechanisms at work. (the downside to the statistical approach is things like witchhunts. If she floats, burn her!) In addition, there is a difference between an observational study and a controlled experiment; they fill different roles in the scientific method. An observational study exists to create potential hypotheses for further experiments, but provides no actual justification of that point.

[0] http://www.nytimes.com/2007/09/16/magazine/16epidemiology-t.html – I was able to access this article a few days ago, but as of 26 Oct 2010 it appears to be behind a registration wall.
[1] http://www.cdc.gov/excite/classroom/outbreak/steps.htm
[2] Pierre-Simon, marquis de Laplace, wrote “A Philosophical Essay on Probability” (more of a mathematical book, if you ask me) almost two hundred years ago, but it is still a good introduction to probability in practice for anyone with a bit of a scientific background.
[3] There is also some discussion of potential error sources at http://en.wikipedia.org/wiki/Epidemiology#Validity:_precision_and_bias

Categories: Uncategorized

Last flight of OV-103

September 22, 2010 Leave a comment

The space shuttle Discovery, OV-103, has made its last scheduled trip to the launch pad down in Florida. The mission is STS-133, delivering a logistics module named Leonardo and other spare parts, and launch is targeted for the first of November. After this mission is only one more scheduled mission, STS-134 aboard Endeavor. Atlantis has already been retired. Discovery will remain on standby until Endeavor’s landing, in case an emergency launch is needed or an additional mission is approved.

I might rant about the space program sometime soon, but in the meantime watch this series of youtube videos. In my opinion, it describes our best shot at Mars, and the best thing is the technology exists, it’s safe, simple, and elegant, and we can be there within a decade.

Categories: Uncategorized

The Distant Starlight Problem…

July 28, 2010 Leave a comment

So, one of the arguments often made against the idea that the Earth is only 6,000 years old, as those with a literal reading of the Bible believe, is that the light from stars further than 6,000 light years away could not possibly have reached the Earth, and yet, we see it.

There are a few responses, such as that the light simply traveled much faster in the past, enabling it to have reached us, or that it was created en route to fool us, but these have their problems. Well, Dr. Jason Lisle of Answers in Genesis has finally found a good solution.

Let’s begin with how science works. Science works by assuming nothing except your own observations, everything else that has been established by science, and that the universe works by a set of simple but uniform laws. We use our observations to draw conclusions about how the world works, and then we test it. If it fails, we draw a different conclusion. If it doesn’t fail, then it becomes scientific fact. Something that many people don’t understand is that science doesn’t say that the world works exactly like the scientific model says. Science just says that the model makes accurate predictions of how the world works. The results are good enough for us to use, but as our instruments get better and our knowledge gets greater, the models might change.

The important point, though, is that science is a way to go from data, to a hypothesis, to experiment, to finally a scientific theory. It’s not a way to go from assumption, to hypothesis, to a scientific theory – but that’s exactly what this creationist is doing. He assumes that the universe is 6,000 years old, and then somehow gets a theory out of it.

The best part is the journal he’s chosen to publish in. Scientists often spend a lot of time thinking about what journal to publish their work in, and this particular one chose one called the Answers Research Journal. That’s right, the same Answers as the Answers in Genesis mentioned above.

He claims to have both Scriptural evidence – if he were a real scientist, he would know evidence comes from data, not an ancient text – and scientific evidence, to support the theory that, paraphrased with care taken to preserve tense, allows distant light to reach Earth virtually instantaneously. I’d love to critique it scientifically, but he hasn’t published it yet. If the journal mentioned does happen to publish this paper (it’s a free online journal) I probably will follow up on this. I’m also very interested in how this works. He says virtually instantaneously, which means it does in fact have finite speed, just very large. One possible approach to critiquing this paper could be to use gravitational lensing of distant objects, assuming that he claims that light still does reach Earth virtually instantaneously.

I don’t know a lot about what he’s saying yet, but he claims that his model makes testable predictions, which is the defining characteristic of science. So we’ll see.

There’s also the fact that our current model states that light travels at the same speed, regardless of where it is, when it is, how old it is, etc. (although the medium through which it travels is relevant), and that that speed is based on a few fundamental constants in electromagnetism and can be derived directly from Maxwell’s equations. There’s no reason to abandon that elegant and accurate model for one which applies different laws based on the light’s age and origin and which is not directly derivable from theory.

It’s people like this that make the rest of you look bad.

By the way, I like one of the comments on Friendly Atheist’s post on the subject. If it can travel faster than the speed of light, then time travel into the past is possible, right? So maybe this guy can go back and find out for himself. If the dinosaurs of 6,000 years ago don’t eat him first, of course.

Intro Post

April 29, 2010 Leave a comment

I’ll be posting an about me page sometime soon, but, well whatever. I’m Dan, a student at Stevens Institute of Technology in Hoboken, New Jersey. I am an engineering student, a science geek, a rational thinker, a political junkie, a technical theater geek. Some people say I lack a soul. I was writing a paper a few weeks ago on a topic I find interesting, and realized how much I enjoyed writing about things I have strong opinions about, have someone critique my argument, and be forced to defend my position. Not only does it give me some academic ‘exercise’, so to speak, it forces me to consider my own opinions and why I hold them. Looking back on one’s own opinions is an important step towards gaining more knowledge, which I consider to be the purpose of life. It either solidifies your opinions because you learn new facts, or it forces you to find new opinions – either way, you know more than you used to.

I said the ‘purpose of life’ back there. I mean that in a practical way, not any metaphysical or theological way. I don’t find it necessary to (or even possible to) attribute my existence to a higher sentience, but rather to the elegant combination of a set of consistent physical laws. I don’t attribute the universe to be some ‘simulation’ of life, as some people do – the suggestion that we are just an alien’s ‘playthings’. I recall a movie ending where our galaxy was shown as part of a cosmic game of marbles played by aliens – I think of it this way: If it’s true, and we can’t prove that it is, there’s nothing that we can do about it anyway – at least, if you replace ‘galaxy’ with ‘universe’. That’s why I don’t try to explain what caused the big bang, much to the dismay of those who question me on such grounds. The┬ásingularity┬áthat occurred at the ‘beginning of time’ quite simply preserved no information from the universe that occurred before it. Explosion of time and space, remember? Every piece of matter and every quantum of energy was located in one point in space and time, and expanded from there. Whatever caused the big bang, we’ll never see it. And the last 13.7 billion years were exciting enough for me, anyway.

So, I’d like to talk a bit about just about everything – from our universe down to our political system. Science, electronics, theater, and most certainly religion are all fair game here. I look forward to talking about it.

So some administrivia. I think the way comments work here is your first comment gets put in a queue. Once I approve it, your comments get to bypass the queue and be posted immediately. I prefer it that way. I’ll be using tags to hit specific (potentially recurring) topics, and categories to hit broader ideas. If I’m talking about someone else’s blog post, I’ll try to send then a trackback. I’m not making any promises about post rate or post consistency – my life gets busy some weeks and boring other weeks. This is a consequence of working in a theater.

Categories: Uncategorized