To the Editor: In their analyses of National Health and Nutrition Examination Survey (NHANES) data and hypertension prevalence, Drs Hajjar and Kotchen1 examined the possibility that the increase in age-adjusted hypertension prevalence between 1988-1991 (NHANES I) and 1999-2000 (NHANES III) could be related to the documented increase in body mass index (BMI). To do so, they used an analysis of covariance to adjust for age, sex, and race/ethnicity, and reported that BMI "contributed to 2%—more than half—of the 3.6% increase in hypertension prevalence."
This analytic approach may have resulted in a spuriously high attributable fraction of the change in prevalence because it did not account for the effects of insulin resistance and/or diabetes. Insulin resistance, an underdiagnosed condition, is associated with increased BMI.2 And, like increased BMI, insulin resistance is an independent, established contributor to the development of hypertension.3 Consequently, the values for attributable fraction reported by Hajjar and Kotchen may be high due to positive confounding.
To determine the unique contribution of BMI to the increased prevalence in hypertension would require adjusting for insulin resistance or diabetes along with age, sex, and race/ethnicity, as well as other confounders in the analysis of covariance. A different analytic approach, such as path analysis, might offer a more accurate estimate than the analysis of covariance used by Hajjar and Kotchen.
Country-Specific Mortality and Growth Failure in Infancy and Yound Children and Association With Material Stature
Use interactive graphics and maps to view and sort country-specific infant and early dhildhood mortality and growth failure data and their association with maternal
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