Wednesday, December 19, 2012

An article published in the Journal of Sports Medicine and Physical Fitness and discussed in a Washington Post blog suggests that students who are more physically fit get better grades.  The article is quick to point out the better grades are not necessarily causally linked with physical fitness.  Let's consider why they may not be causally linked but also consider the impact on cost-effectiveness analyses of physical fitness interventions if the causal link is real.

First, why may they not be causally linked? Among adults, it is quite possible that those who are more physically fit have more "self-determination" or "drive" or a greater sense of "self-efficacy" in general. If true, that could imply that those who are more likely to take the time to become physically fit or maintain their physical fitness are also more likely to succeed in other areas.  Among students it could mean that those whose parents encourage doing well in school also encourage doing well in other things and also take the time to monitor and manage their children's physical well-being very closely.  So, there are plenty of reasons that these two concepts may be correlated but the relationship may not be causal.

But suppose for a moment, that the relationship is causal. Suppose that being more physically fit makes a person better able to concentrate and maintain their concentration.  Suppose that being more physically fit enables a person to learn better if they are also more socially and mentally healthy as well as physically healthy.  There are lots of possibilities here.  What, then, would we need to do to fully appreciate the value of physical fitness programs?

First, we would need to make sure that to the degree that improved physical fitness enhances fitness in other domains of health, this is recognized and incorporated into the results. In other words, the health related quality of life impacts of physical fitness may go well beyond making someone just more vital or decreasing obesity or the eventual risk od diabetes and other complications of a lack of fitness.

Second, we would need to establish a link as to how much fitness improves grades (or learning more generally) and how that translates into a person being more productive and what the economic value of that productivity might be.  In fact, the productivity could also have an impact on physical and mental health later in life.  So, the relationship could actually be part of a favorable feedback loop that could have a large economic value throughout life.  Failing to capture this feedback loop in any long term predictions of the impact of a childhood fitness campaign could great understate the campaign's value.

Of course, we have plenty of money being spent on fitness for kids already.  Perhaps we do not need more.  But as we continue to consider how to use the limited public dollars for both health and education, we might want to consider how these two interact and efficiencies that can be gained from thinking about the two together.  Failing to do so may lead to inefficient resource allocation.  But doing so is certainly no simple matter.  And going so will require more data and a fairly sophisticated modeling exercise to incorporate all the possible effects of fitness on education and vice versa.   

Cost-Effectiveness of Preventing Complications of Childbirth

Back on December 10, the Wall Street Journal had an article on the increasing incidence of complications at childbirth and commented on this could be related to the increase in age of the mother in many cases, obesity, and mothers having other chronic conditions.  Although the article was quick to point out that complications were not confined only to women with complicated health of their own and that otherwise perfectly healthy mothers could also have severe complications.

The article also pointed out that most safe birth initiatives in the past had focused on preventing harm to the infant.

What is interesting about this from a cost-effectiveness perspective is the question of whose benefits are counted.  In general, when it comes to birth we should count both the mother and the child.  And, not only would we want to count each of them, but we might also want to find a way to recognize that their health is closely intertwined.  For example, a mother losing a child could have a long-term effect on the mother's mental health.  And, if it affects her mental health it could also have an impact on her physical health.  The same might be said of an infant losing her mother.

When we see sophisticated cost-effectiveness analyses that calculate and use quality adjusted life years, we find that usually this focuses on a single target group.  In this case the mothers (if we are focusing on preventing or dealing with complications of birth) or the children (if we are focusing on the child's health immediately after delivery).  What we rarely see in the literature is the combination of the two.  And what we see even more rarely would be an explicit recognition of how the two are not just correlated but so closely interrelated.  A loss of health related quality of life or life years for one member of the mother-child pair is likely to have a critical impact on the other.  This is an interesting frontier to think about and to consider how acknowledging the impact on both members of a pair might make specific interventions looks like a better value as the impact is increased by considering the effects on two individuals.   

Tuesday, December 11, 2012

Looking at Statistics in Isolation Can Lead to the Wrong Conclusions

One aspect of public health is violence.  For example, at the Johns Hopkins Bloomberg School of Public Health we have a Center for Gun Policy and Research.  And, recently, there has been a lot of violence in the local news.  That, of course, is on top of numerous stories about gun violence nationally and internationally over the past several years.  So, it may seem like we should be looking for more ways to incentivize against violence and to find cost-effective solutions to preventing gun violence in particular and all types of violence in general.

In contrast, if we looked at the fact that the rate homicides appears to be going down, we might wonder, "Well, is there a problem with our perception of violence?  Maybe it is just lots of anecdotes and we don't need to look for more solutions or allocate more resources."

A piece in the Wall Street Journal recently entitled "In Medical Triumph, Homicides Fall Despite Soaring Gun Violence," (which is not available for free) they looked at this issue.  What the article reported on was an improvement in the survival after being shot in recent years.

Now, we could ask whether heroic treatment after gunshot wounds is cost-effective.  It is definitely expensive.  The trauma centers that have been set up to treat such patients (and that contribute to the much higher survival rate) have high fixed costs and high variable costs.  The WSJ article indicates that they deal with a great amount of uncompensated care in our current system and are reported to lead to losses for the hospitals at which they are located.  Thus, the demand for resources from society and resources that are taken away from the hospital are notable.  Importantly, I am not saying that we should not be saving lives.  Only that we need to be cognizant of the costs of saving the life and cognizant of the additional costs during any rehabilitation phase afterwards.

Then, once we are aware of the costs, we might ask whether the medical triumph is the most economically favorable way to decrease deaths from guns or whether we might be better off economically by trying to limit gun violence as a way to limit deaths rather than needing to treat those who do suffer gunshot wounds.

The contrasting inferences one might make based on different pieces of the data and even the contrasting steps one might take in structuring a cost-effectiveness analysis (e.g., comparing only prevention methods or only treatment methods or treatment with prevention) illustrate how important it is to try to assemble all relevant data before making a decision on further resource allocation and the need for and usefulness of economic evaluations.