Wednesday, June 1, 2011

Mortality, Mauling, and Maiming by Vicious Dogs Part 1

A well-researched retrospective study includes a lot of caveats and limitations the authors themselves experienced in both cataloging and understanding the information at hand. Like if you read the actual text of this study, there is a whole discussion on the concerns with accessing past case histories of dogs who died at 27 veterinary teaching hospitals.

Studying the reasons for why dogs died at various veterinary hospitals does not generally result in too much controversy.

This is going to be a multi-part series, because I want to challenge you. I want to challenge myself! You might be surprised by some of my thoughts on the article.You might not.

A recent study in the Annals of Surgery has inspired - on both sides of the issue - a lot of discussion. On one side are the people who, for whatever reasons, either dislike Pit Bulls or wish to legislate or ban them. On the other side are the people who, for whatever reasons, like Pit Bulls and don't want to see them legislated against.

The study (title same as this post's title) is a retrospective analysis of dog bites that required individuals to be admitted to the level 1 trauma center of a teaching hospital in San Antonio (which is not explicitly stated in the article, poor form authors, poor form).

What each side says about this particular analysis is indicative of their personal opinions and biases. Reading each side might make you believe they are talking about two different studies! The anti-Pit Bull folks sing the praises of the article, methodology concerns be darned! Pit Bull advocates try to find every perceived problem, writing off the article as a biased piece of tripe that somehow managed to get published in one of the most prestigious surgery journals in the world (see the problem there?).

Both sides and, to some degree, the authors of the study are guilty of confirmation bias.

When I read the article, I was guilty of it too. So I took a breather, a step back, and with fresher eyes and a calmer heart, evaluated the article based on its own merits (after all, it is published in an established peer-review journal) and assessed the drawbacks as well. My bias will show through, but I have done my best to review this article in fairness.

Most peer-reviewed journal articles follow the following outline:

Introduction: The "problem" is presented and authors provide an abstract overview of the journal article. Background information is provided. It primes you for what to expect.

Materials and Methods: What type of data is used to support their hypothesis and how is it analyzed? Should include the specific statistical analysis performed, database used to organize and read the information,  any source information, when and how that information was obtained, classification/scale of information, etc. It gets as detailed as possible.

Results: This is all the statistical data obtained. It is supposed to be an impersonal, descriptive presentation.

Discussion: This is when authors are given more room to discuss the implications of their results. Setbacks, problems, caveats, possible issues with data sources or how they were organized. Supporting evidence from previous studies. It's a chance for researchers to offer suggestions on future research or ideas on possible ways to prevent unwanted outcomes (like dog bite fatalities, in this particular study's case).

Conclusion and Implications: Shortest part, offering a quick summation of suggestions to various audiences.

"Mortality, Mauling, and Maiming by Vicious Dogs" opens with a "case presentation" from a 2009 dog-bite fatality in Texas. It is an interesting way to open a research article. I have not found it to be common in animal welfare studies, but perhaps surgery journals often have case presentations.

The authors of the article start off with an inaccuracy, stating the age of the infant was 11-mos-old. According to the obituary of the child, he was nearly 8-mos-old.

The case presentation describes the attack and briefly the medical wounds the infant suffered. It neglects to include possibly pertinent information, like that the dogs (two un-neutered males) had mauled another child several years ago, and that they had bitten other people. (As an aside, the owner of the dog's - the child's grandmother - faced nearly 20 years in prison but died before her trial).

Concerns with the introduction - issues of defining a problem or making one exist

The Introduction of the article states that "dog bite injuries are a serious public health concern."

This depends on how you define "dog bite injuries". Is a nip from a dog a "dog bite injury" or a "serious health concern"? Is a bite that breaks the skin but only requires a small bandage a "dog bite injury" or a "serious health concern"? Or is it the more significant bites that cause enough trauma to require hospitalization, reconstructive surgery, or even worse, death that would be considered a "dog bite injury".

If you define a "serious health concern" or a "dog bite injury" as any negative interaction between a dog and a human that results in teeth on skin, regardless of severity, then 1.5% of the population would be included - that ubiquitous 4.7 million number.

If you define "dog bites as serious public health concern" as those bites that cause enough injury to require a trip to the hospital, hospitalization, reconstructive surgery, or tragically ends in death, then the numbers are different. Approximately 800,000 people require medical treatment annually; of those, nearly 300,000 will require admittance to a hospital. Of that figure, 31,000 require reconstructive surgery, and of all dog bites, 20-30 people will die. That means 0.0000098 - 0.2% of the population is affected.

The former would fairly be considered a serious health concern (although arguably "dog bite injury" is a bit loose). The latter would fairly be considered less of a serious public health risk (and "dog bite injury" would be more medically accurate).

The authors do not choose to define a "dog bite injury", which would be fine if that was not pertinent to the article, but it is.

With such an emotionally charged issue as "death by man's best friend", I shouldn't have to, but I will make clear that in no way am I diminishing the suffering, loss, or trauma of a dog attack or dog bite fatality. Any preventable death or mauling is incredibly tragic.

But I would like to put this into perspective. Numbers alone are not useful. They can often make us believe there is a problem where none actually exists. Or the problem is not as bad as previously thought. Or maybe it's worse! What is more useful is not raw numbers but rates. The rate of something measures how likely an event is going to occur. Crime rates are often measured per 10,000 people. Disease or public health risks are measured per 100,000 people, generally.

For example, the death rate for cardiovascular disease is 184-190 deaths per 100,000 people. The national average of cancer death rates is around 178 deaths per 100,000 people. The dog bite related fatality death rate is 0.07-0.08 per 100,000 people. The death rate for vehicular deaths is, on average, 14.4 deaths per 100,000 people. You have a pretty low risk of dying by dog bite. And you have a pretty low risk of being significantly harmed by a dog.

The CDC tracks causes of deaths - you can read a numbers reports here.  Thankfully, dogs are a relatively "safe" public health concern. They do not make it in the top ten cause of death at any age.

Part II: The Problem with the AKC and the Problem with Pit Bulls...coming soon.

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