In Reply We thank Bernard for his interest in our article published in JAMA Neurology.1 Bernard raised several questions regarding the interpretation of our results and the potential for unmeasured confounding to affect the findings we reported.
First, he raises the issue of serum levels of persistent organic pollutants changing because of adiposity change. In the literature, there are conflicting data regarding this hypothesis and the few positive studies all involve obese individuals with rapid and massive weight loss. Bernard cites work from De Roos et al.2 However, Figure 3 and Table 3 of this article clearly showed no statistically significant change in serum dichlorodiphenyldichloroethylene (DDE) levels based on weight loss. This is similar to that observed in a controlled weight loss study that also noted no change in serum DDE concentrations as a function of weight loss.3 The strongest predictor for serum organochlorine concentration is age,4 which we controlled for in our study. Therefore, it is highly unlikely that any weight loss that might have occurred would confound our data but future studies could address this possibility.
Richardson JR, Levey AI, German DC. Elevated Serum DDE and Risk for Alzheimer Disease—Reply. JAMA Neurol. 2014;71(8):1056. doi:10.1001/jamaneurol.2014.1548