We were pleased to see the article by Pladevall et al. (1) in a recent issue of Diabetes Care, as it extends our prior results to Spanish and Mauritian samples. While the authors suggest that their findings differ from our results in the Normative Aging Study (2), we wish to clarify that we had previously demonstrated that a single factor underlies components of the metabolic syndrome using confirmatory factor analysis.

In our report, we showed that 10 risk factors associated with the metabolic syndrome were predicted by one primary factor, albeit through subfactors of insulin resistance, obesity, lipids, and blood pressure. The report of Pladevall et al. and the recently published review by Kahn et al. (3) refer to our model as a “correlated-factor model” or “four-factor model.” However, our analyses went well beyond a model of correlated factors to establish that the four subfactors were not only correlated but indeed predicted by a single common factor (second-order factor) (Fig. 1 in ref. 2), which we labeled the metabolic syndrome. Furthermore, it should be noted that with a second-order factor, we have found that it is possible to include the full complement of components of the metabolic syndrome in confirmatory factor analysis. For example, it is possible to include both systolic and diastolic blood pressure, consistent with current metabolic syndrome criteria, rather than mean arterial pressure alone.

Pladevall M, Singal B, Williams LK, Brotons C, Guyer H, Sadurni J, Falces C, Serrano-Rios M, Gabriel R, Shaw JE, Zimmet PZ, Haffner S: A single factor underlies the metabolic syndrome: a confirmatory factor analysis.
Diabetes Care
Shen BJ, Todaro JF, Niaura R, McCaffery JM, Zhang J, Spiro A 3rd, Ward KD: Are metabolic risk factors one unified syndrome? Modeling the structure of the metabolic syndrome X.
Am J Epidemiol
Kahn R, Buse J, Ferrannini E, Stern M, the American Diabetes Association, the European Association for the Study of Diabetes: The metabolic syndrome: time for a critical appraisal: joint statement from the American Diabetes Association and the European Association for the Study of Diabetes.
Diabetes Care