Clinical Evidence, Searching Tidbits, and Other Minutiae
Friday, August 15, 2008
Tuesday, August 12, 2008
Confounding is a concept often mentioned in clinical research - the idea that a 3rd variable can distort or confuse (or confound..) a relationship between two other variables.
When confounding is present, it looks like exposure A is associated with increased risk of disease B, but really a 3rd variable X is causing increased risk of disease B and it just happens to also be associated with exposure A.
Clear as mud? Here's a real world example - if you look at how people recover after hip fracture, and you consider gender and whether women or men do better after hip fracture, it may seem that women generally fare poorly after they break a hip.
However, there's a confounder in this relationship -- age!
If you think a little more about the characteristics of people who break a hip, you realize that young men have hip fractures (due to high-energy trauma associated with events like motor vehicle crashes) and old(er) women have hip fractures (women with reduced bone density and potentially some mobility/balance/cognition problems leading to a fall). Younger females don't tend to have as many hip fractures as their young male counterparts (due to lifestyle issues etc.), and older males don't tend to have the same incidence of hip fracture as their female counterparts (they don't always have the same severity of bone density changes as older females; men tend to die sooner).
The female group is then naturally weighted toward older people (who generally heal more slowly and may have other comorbid conditions going on) and the male group is weighted toward young, otherwise healthy people.
So, when you add age to the statistical model and correct for the different age distribution, the difference in outcome by gender goes away -- the women tend to do more poorly because they're older, not because of their gender. If you control for age, there's no difference in outcome between men and women.
This is a classic example of confounding and one way to correct for it -- in an observational study, you can't randomize, but you can try to measure "things" that might be impacting your disease -- age, gender, socioeconomic status, family support, severity of injury, type of operative repair, rehabilitation status, etc. -- so that you can add them into your statistical model.
The Pitt epidemiology supercourse has a great discussion of confounding and ways to correct for it (PowerPoint file), and the Social Sciences Statistics blog has a very interesting post today that comments on issues of confounding in a recent study about running habits in older individuals (this is the study the post talks about).
Saturday, July 26, 2008
One of the best library training videos ever
From Mississippi Public Broadcasting, a video series called Tomes & Talismans about the Dewey Decimal System. Sound boring? But...it uses a sci-fi backstory -- aliens named Wipers from the Black Star Solar System have taken over the Earth,including destroying the intercontinental satellite system (which oddly looks a lot like a Jeopardy! quiz screen).
Because you know what Wipers like to do for fun?
They get down by destroying communication and data technology.
Don't worry - humans are evacuating to the White Crystal Star System (using a teleportation system that reminds me of the TV device in Charlie and the Chocolate Factory, and don't worry, they tested it on a cute little puppy first, then on some kids, to make sure it was safe).
A courageous librarian (in a fantastic khaki vest, I might add) is one of the last to go, making sure all the books are organized in the card catalog so that anyone returning to the planet will know what happens...
The whole series has been uploaded to YouTube.
(via Best Week Ever)
Tuesday, July 08, 2008
Hopkins on ABC
ABC is posting the full episodes of the short series "Hopkins" filmed at Johns Hopkins Hospital in Baltimore... the kind of reality show I can watch while not feeling (very) guilty or voyeuristic :) And a good way to learn some more medical terminology and see some of the concepts "in action".
Episodes are online here and this page has an overview of the show in general.
Tuesday, June 17, 2008
Unofficial impact factors
Biomed Central has calculated unofficial impact factors for many of its titles that are not yet covered in Journal Citation Reports -- they used ISI data to figure out the IFs for ~100 BMC titles. Seems like a great way to work around the delay between when a journal begins publication and when ISI begins tracking/calculating IFs.
More here on the Biomed Central blog and here on the BMC Impact Factor FAQ.
Friday, June 13, 2008
Friday humor: David Sedaris
The Fresh Air David Sedaris interview is up on the NPR site -- he talks about his latest book (When you are engulfed in flames).
(he's touring now too -- dates are up in Ticketmaster, including a Nashville date this fall!)
More on procrastination
This feature on NPR's Talk of the Nation fits in really well with my ongoing struggle to trick myself into doing things that I need to do but don't really want to do :) -- How to Be a Productive Procrastinator
Why do today what you can do the day after tomorrow? Procrastination expert Timothy Pychyl and self-professed "structured procrastinator" John Perry discuss the latest research on this type of behavior and how to prioritize what's really important.
including "the inner mechanics of lolly-gagging"...
And here's one of my favorite cartoons ever - "Tales of Mere Existence: Procrastination"