Nonsense Science and Persuasion
24th January 2008
What? What?
Ripped from the headlines of the New England Journal of Medicine:
“Results. In 5,063,622 person-years of follow-up, 10,235 men and 4318 women for whom childhood BMI data were available received a diagnosis of CHD or died of CHD as adults. The risk of any CHD event, a nonfatal event, and a fatal event among adults was positively associated with BMI at 7 to 13 years of age for boys and 10 to 13 years of age for girls. The associations were linear for each age, and the risk increased across the entire BMI distribution. Furthermore, the risk increased as the age of the child increased. Adjustment for birth weight strengthened the results.
Conclusions. Higher BMI during childhood is associated with an increased risk of CHD in adulthood. The associations are stronger in boys than in girls and increase with the age of the child in both sexes. Our findings suggest that as children are becoming heavier worldwide, greater numbers of them are at risk of having CHD in adulthood.”
This is from an article entitled, “Childhood Body-Mass Index and the Risk of Coronary Heart Disease in Adulthood,” authored by Jennifer Baker and colleagues. (You can read the entire article here.)
First, let me congratulate Dr. Baker who is listed as a post doc researcher at the Institute for Preventative Health in Copenhagen. She must be bouncing off the walls right now because a NEJM vita hit as a post doc is a major accomplishment. Lots of joy and happiness with the Baker people and her colleagues.
Second, let me sharply disagree with just about everyone connected to this research. The abstract notably omits any quantitative values in the Results portion which is fishy given that this is an epidemological study which means it’s only about numbers. Instead we get the rhetorical weasel word, “significant,” as the standard by which we understand the outcomes. See, kids who are heavy have “significantly” more heart disease as adults compared to kids who are lighter.
Sounds signficant, doesn’t it? Certainly the reviewers and editors at the New England Journal of Medicine thought it must be . . . significant. So what are the numbers? I mean, we’re all adults here, the children are in bed, so we can speak frankly.
The relative risk for heavy kids is 1.10.
That means, for example, if light kids have a rate of 10 per 100,000 for heart disease, then heavy kids will have a rate of 11 per 100,000. I’d give you the actual numbers from the study, except that the researchers did not provide the absolute rates or if they did they described them so poorly that I cannot tell for sure what’s going on. They do provide a lot of Tables with various relative risk ratios none of which exceed 1.10.
This is an absurb study and it is absurd that the NEJM published it and it is absurd how it is presented.