Good and Bad Epidemiology and Other Interesting Links

1. The incomparably intelligent and eloquent Sanjay Basu on how doctor house calls of the olden days could return - in the form of targeted efforts to reduce preventative disease and hospitalizations on the basis of cutting edge epidemiology.

2. A man after my own heart, Dr. Ben Goldacare, an evidence based medicine expert, rails against bad epidemiology studies (you know, the kind in the news that like say coffee is protective against cancer or something like this, only to be overturned 180 degrees two months later) in this entertaining TED talk. Some useful pointers about how to differentiate between junk and good research as well as a good summary of causal inference. (HT: Jeremy Green)

3. Apparently there is enough sense to go around for all of us.

4. Asif Mandvi of The Daily Show lampoons the Republican candidates position on science and scientific knowledge in this great clip. Its pretty funny, until you realize that the candidates are actually serious. Then its a little scary. (HT: Kim Kopecky)

5. How does the recession and being out of work influence our physical activity? And what are its implications for health? Gregory Colman and Dhaval Dave explore these issues in an interesting recent NBER working paper.

Bad Epidemiology

While in South Africa a few months ago, an irritating yet clever radio announcer, during a joke-based interlude between songs, made the following comment:

"Research has shown that insomnia leads to depression. Other research has shown that depression leads to insomnia. Still other research has shown that research leads to more research."

Seems like a great indictment of some of less-than-careful, data mining-y studies that often find their way into decent journals and on the evening new. (Note: I'm not anti-epidemiology.)

New Link and Some Random Notes

1. Fellow Yalie Paula Chatterjee has just started blogging from Uganda, where she is working on a summer project educating and empowering commercial sex workers in Kampala. Paula is thoughtful, articulate and intelligent, and her first post marks the start of what should be an interesting blog. Indeed, the writing reminds me of James Hudspeth's travel blog, which has since expanded to a blog about all things (congrats to James, by the way, for his well-deserved acceptance at the Brigham and Womens Internal Medicine Residency Program). Both blogs are linked in the sidebar.

2. Great NYT article on Dark Matter and the search for the Theory of Everything. I've recently gotten into popular science writing, and I am working through James Gleick's biography on Richard Feynman right now. It's great stuff, and I am planning on reading the latest Einstein biography as well as a book on the history and significance of E=MC^2.

3. Speaking of science writing, I am trying to find a good book on the periodic table of elements. I've been intrigued by this ever since 8th grade, when we learned about how scientists converged on the periodic table and predicted the existence of many hitherto undiscovered elements. I found this book: any thoughts?

4. Is there an economics theory as powerful as the periodic structure of elements in making predictions about the future and/or unknowns?

Hepatitis B and Pro-Male Sex Ratios Revisited

Many of you are probably aware of Emily Oster's controversial study on the potential (causal) effects of Hepatitis B on population gender ratios (see here for a non-technical summary). Oster's paper sparked a great debate as to whether the disease could truly explain a significant portion of the gender imbalance in many of the Asian countries, such as China, where the male/female ratios are remarkably large. Oster and Gang Chen recently revisited the Hepatitis B hypothesis as it applies to China. Their findings:

Earlier work (Oster, 2005) has argued, based on existing medical literature and analysis of cross country data and vaccination programs, that parents who are carriers of hepatitis B have a higher offspring sex ratio (more boys) than non-carrier parents. Further, since a number of Asian countries, China in particular, have high hepatitis B carrier rates, Oster (2005) suggested that hepatitis B could explain a large share - approximately 50% - of Asia's \missing women". Subsequent work has questioned this conclusion. Most notably, Lin and Luoh (2008) use data from a large cohort of births in Taiwan and find only a very tiny effect of maternal hepatitis carrier status on offspring sex ratio. Although this work is quite conclusive for the case of mothers, it leaves open the possibility that paternal carrier status is driving higher sex offspring sex ratios. To test this, we collected data on the offspring gender for a cohort of 67,000 people in China who are being observed in a prospective cohort study of liver cancer; approximately 15% of these individuals are hepatitis B carriers. In this sample, we find no effect of either maternal or paternal hepatitis B carrier status on offspring sex. Carrier parents are no more likely to have male children than non-carrier parents. This finding leads us to conclude that hepatitis B cannot explain skewed sex ratios in China.

For what it's worth, I applaud Oster, who is clearly a top-flight researcher doing interesting work, for her academic courage and honesty. It's just great to see an example where one's ego does not interfere with his/her quest to learn the Truth. Good lesson for graduate students such as myself.

Furthermore, despite this retraction (at least with respect to China), Oster is not leaving the topic behind. Indeed, the fact that Hepatitis B explains a good deal of the gender imbalance in some countries but not others is intriguing and worthy of further exploration. This is exactly what she is doing this new working paper, which attempts to reconcile the scientific and population evidence on Hep B and sex ratios.

Excellent research on an interesting line of work. I'd be curious to see how this plays out in the future.

[Ed - 5/13/08 - I was recently informed that the Marginal Revolution blog put up a very similar post yesterday on this topic. Just for the record, I wrote this post as soon as I saw Oster's NBER working paper, and prior to me finding out what other blogs had to say. Also, just as an FYI, you might want to check out the comments under said MR post. The discussion there is pretty interesting.]

Fetal Origins Plus

I've spent some time on this blog talking about the influence of fetal and early childhood events on later health and economic outcomes (see, for example, here). Recently, I was scouring the web for some of the medical literature on this subject, and came across this great website. The site summarizes the seminal body of work conducted by David Barker and colleagues on the fetal origins hypothesis, providing non-technical summaries of a variety of research strands and key citations to the most important papers written on the subject. Definitely check it out.

As I mentioned in the linked post above, the fetal programming literature has gained great currency among economists. However, little work has been done on fetal origins in the context of other investments and events and individual receives or faces in the course of his or her life cycle. James Heckman's recent paper in the Proceedings of the National Academy of Sciences synthesizes these literatures, linking health, cognition and other skills in the process (you can find a more general statement of Heckman's research agenda here). It's a great read that highlights the fact that there is a great deal of research required to fully understand and characterize many aspects of human capital accumulation. (Self-promotion: this is good news for me, as much of my dissertation deals with these topics.)

Elementary, My Dear Watson

Nobel Prize winner James Watson created quite the ruckus this past week thanks to his comments on race and intelligence. His basic thesis is pretty easy to distill:

The scientist, who won the Nobel prize for his part in discovering the structure of DNA, was quoted in an interview in The Sunday Times saying he was “inherently gloomy about the prospect of Africa” because “all our social policies are based on the fact that their intelligence is the same as ours - whereas all the testing says not really.”

Watson recently clarified his statements, probably in an attempt to address the tidal wave of criticism hurled in his direction. His new material, while sticking to his main point, sounds less inflammatory:

-"If I said what I was quoted as saying, then I can only admit that I am bewildered by it."

-"We do not yet adequately understand the way in which the different environments in the world have selected over time the genes which determine our capacity to do different things."

-"This is not a discussion about superiority or inferiority, it is about seeking to understand differences, about why some of us are great musicians and others great engineers."

I'm not going to call Watson a racist or anything like that: it would be scientifically unproductive and irrelevant to do so. Instead, I'd like to address the merits of his hypotheses. Here is what I think:

1) Unless humans evolved independently in more than one location, all of us have descended from the same human line and, therefore, some specific geographic location. Obviously, as human migrated away from each other differential selection pressures helped generate different traits (like skin color, facial morphology, etc). In that sense, its not hard to imagine that different population groups might vary across a set of traits. However, it is harder to imagine that something like intelligence would be selected on differently across space: I would expect the returns to being smart to be relatively similar across different populations, especially in the days around and prior to the agricultural revolution.

You might think that this argument is as tenuous as Watson's. You are right. However, my point is to apply the "huh" test to his reasoning. When one does that, the whole thing seems somewhat shaky.

2) Here is a stronger argument: racial gaps in ability might be explained primarily by differences in childhood investments and early life environments. Indeed, there is a great deal of scientific evidence that indicates that this may be the case. I'll pick one of my favorites as an example. In an earlier post, I talked about a paper by Douglas Almond and Ken Chay, looking at the impact of Civil Rights movement induced hospital integration on the intergenerational transfer of health status among black individuals. The authors found that the children of women born just after hospital integration report higher birthweights, better apgar scores, and lower infant mortality. Here's the kicker: they also find that the black-white test score gap among this advantaged cohort is much thinner.

It's no stretch to posit that the effects of environment are large, powerful and very real. Given how salient these factors are, it makes a great deal of sense to try and understand the process of cognitive development and its relevant inputs before resorting to blanket genetic statements. Indeed, other papers suggest that the entirity of the ability gap can be explained by early-life socioeconomic factors. Check out this post by Steven Levitt for some information on his interesting work.

3) Uncovering the determinants of ability should command a great deal of research attention. All credible hypotheses should be taken seriously and addressed with the best scientific methods. On that note, I do not believe that Watson's hypotheses are very compelling, and perhaps this is not where we should be focusing our attention when it comes to future research.