In Reply: In response to Dr Matuchansky, the strength of NHANES III compared with the continuous NHANES cohorts lies in its larger sample size, greater number of geographic areas, and availability of mortality linkage beyond 10 years. While the study by Ibrahim et al1 used continuous NHANES to compare prevalence of coexisting conditions, it actually used life tables from the National Center for Health Statistics for survival comparisons, reflecting the significant limitations of the continuous NHANES cohort for this purpose. Matuchansky points out that the average death rate for the US population was 17% lower in 2005-2006 than in 1990-1994. However, 2 effect modifiers must be considered: this difference in death rates is age-dependent, and this difference occurs among the average person rather than among healthy individuals who would be eligible to donate kidneys. Even given these limitations, the difference in mortality between live donors and NHANES III controls was much greater than 17%, as illustrated in Figure 1 of our article, so our inference that live donation was not associated with excess mortality would still hold.
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