Data look different with kids at stake

Researchers at Children's Hospital in Cincinnati are surprised that the state of California has passed a law requiring schools to address the issue of backpack weight carried by children. They aren't surprised that parents and educators are concerned about children's risk of injury from improper use of backpacks. They aren't even surprised that a study in the May issue of Spine found a 74% rate of self-reported back pain among backpack users.

But they are surprised at the zeal with which the self-reported data have been embraced, particularly when their own research shows that children whose back pain necessitates a clinic visit rarely associate their pain with backpack use (see "Backpack flak: Experts clash over extent of risk," page 24).

They shouldn't be surprised. When it comes to public opinion, self-reported data can be as powerful as the most meticulously controlled laboratory findings-especially when children's health is at stake.

Just ask Bill Montelpare, MD, who headed a three-year research project to determine whether Canada's national youth hockey association should lower the age at which body checking was permitted from 14 to 9. (In the U.S., body-checking is permitted at age 11.) For three seasons, Montelpare and colleagues studied injury rates as well as factors affecting the flow of the game, such as penalty minutes, in a test district of youth players who were allowed to check and compared the findings to those for players in the same age group who were not allowed to check.

Montelpare found no statistically significant difference in injury rates for the two groups, based on insurance claims filed with the Canadian Hockey Association's injury database. Based on these findings, the CHA announced before the 2002-2003 season that participating leagues would be allowed to implement body-checking for 9- and 10-year-olds; four of the CHA's 13 leagues chose to do so.

But when reporters from the Canadian television program "Disclosure" looked at Montelpare's findings, they focused on the study's self-reported injury rates, which were four times higher in the checking group than the non-checking group. Of course, it didn't help Montelpare that the television reporters also noticed that the calculations had overstated the number of at-risk players. But even after that error had been corrected, the claims data still indicated no significant difference between the groups-and yet the media and the public remained focused on the self-reported numbers. The CHA reversed its earlier decision and announced in May that body-checking would be implemented only at age 11 or older.

If the distinction between insurance claims data and self-reported data was lost on hockey-mad Canada, where many youth coaches believe that injuries associated with checking might actually decrease if correct techniques were taught at a young age rather than when players are hitting puberty, it shouldn't surprise anyone that self-reported backpack data are packing an equally powerful punch.

Truth be told, the risk of injury in either scenario is more complicated than any study has yet been able to measure. Just as the risk involved in body checking, defined as using the hip or shoulder to separate an opponent from the puck, depends on the "goon mentality" of a player or coach, the risk involved in backpack use depends on factors such as how the pack is worn and how the weight in it is distributed.

The bottom line, of course, is liability. No parent, coach, or administrator wants to be responsible for a child's injury, no matter what flavor the data documenting the risk of that injury might be.

And that shouldn't be surprising to anyone.