A mini-primer on epidemiology for dietitians
Caveat lector: I am not an epidemiologist. (If you've been reading this blog, I'm sure you already knew that.) I also do not have a graduate degree in research. But I have completed Dietitians of Canada's (DC) Evidence-Based Decision-Making (EBDM) course so if anything, I am more aware of what I don't know. And I'm working on becoming more evidence-based by selectively acquiring, critically appraising and judiciously applying the literature. If this sounds like considerable mental effort requiring hours of concentrated reading and reflecting, well it is and it does. But the results are worth the time and energy inputs: I have greater confidence I am using"best practice" based on information that is up-to-date, valid, makes a difference to outcome, and applies to the specific situation.
Gary Traubes' recent New York Times Magazine article, Do we know what makes us healthy? (see previous post) motivated me to review my very rudmentary knowledge of epidemiology. If you've read this article you will recall the author extensively discussed the different types of potential bias in epidemiological studies. Mr. Traubes ended his article with the guiding principles "skeptical epidemiologists" recommend:
- "[A]ssume that the first report of an association is incorrect or meaningless, no matter how big that association might be."
- "If the association appears consistently in study after study, population after population, but is small — in the range of tens of percent — then doubt it."
- "If the association involves some aspect of human behavior, which is, of course, the case with the great majority of the epidemiology that attracts our attention, then question its validity." (The exception to this rule: pay close attention to an association of unexpected harm.).
- In summary, "remain skeptical until somebody spends the time and the money to do a randomized trial and, contrary to much of the history of the endeavor to date, fails to refute [the results of the epidemiological study]."
This skeptical or "question everything" mindset is part of what I learned in my EBDM course, which equipped me with tools and build knowledge and skills to critically evaluate whether a study is valid (true), important (clinically significant) and applicable to the specific situation.
You can read an overview of the 10-unit interactive online course here. I believe DC will be offering the course at least once in 2008. The current course is already in progress.
In the meantime, you can begin self-directed study on evidence-based practice by using online resources. Over the next couple of weeks, I will share ones that I've found helpful.
Here are some resources specifically about Epidemiology:
Epidemiology Supercourse (a link on UBC's Health Care & Epidemiology so I feel confident recommending it)
You may find it easiest to navigate the site by going to the page that is organized by topic. Here are some basic courses that I liked because they had detailed speaker's notes in addition to the slides.
Descriptive Epidemiology for Health Professionals (4-part series)
Different Kinds of Epidemiologic Studies
Potential Errors in Epidemiologic Studies (a good one to read before or after the NYT Magazine article)