Method errors or unexplained biological information?

Letters to the Editor will be published, if suitable, as space permits. They should not exceed 1000 words (typed double-spaced) in length and may be subject to editing or abridgment. Left ventricular mass (LVM) is an indicator of cardiovascular status, integrating multiple adverse pathophysiologic influences and a potent, independent predictor of prognosis, making definition of optimal methods to distinguish abnormal from normal LVM a matter of high clinical priority. Different methods have been used to account for body size in the definition of " normal " LVM, and there is agreement that the ratiometric approach is not sufficient to capture the extend of abnormalities, especially in obese populations. 1 In the July issue of Hypertension, Chirinos et al 2 studied apparently normal members of 2 adult populations aged 35 to 55 and 45 to 84 years old and proposed a new exponent of body height (height 1.7) to normalize LVM. This exponent is substantially lower than the allometric signal (height 2.7) that we initially proposed , 3 from a normal-weight population including infants, children , adolescents, adults, and elderly. It is also lower than other allometric powers (2.5 to 3.0) identified in other young populations and even lower than the exponent of 2 proposed by the Framingham Heart Study in an adult population. The allometric approach to identify left ventricular hypertro-phy (LVH) increases the prevalence of LVH, without decreasing the LVH-associated relative risk, 4,5 thus increasing the population risk attributable (PAR) to LVH. 4,5 PAR is the proportion of the incident disease (cardiovascular event) in the (exposed and nonexposed) population that is attributed to the exposure to a risk factor (LVH). PAR, therefore, represents the potential number of events that could be avoided by removing the exposure, thereby identifying risk predictors most relevant for public health. We measured PAR of different methods to define LVH in the cohort of the Strong Heart Study, 4 using partition values for definition of LVH, obtained from a reference normal population of the same cohort (using meanϩ1.96 SD). We found that normaliza-tion for height 2.7 maximized PAR for composite fatal and nonfatal cardiovascular events, compared with all other methods, both in the whole cohort (15.54%) and in the hypertensive subpopulation (16.58%), at similar (or slightly lower) age-and sex-adjusted hazard ratios. Because the prevalence of obesity is very high in the Strong Heart Study cohort, another population from Italy was also studied, the Massa Ventricolare …