In Reply: We agree with Dr Paz-Filho and colleagues that leptin levels show variation throughout the day,1 but we believe that this would lead to some random misclassification rather than confounding. It is unlikely that the degree of misclassification in leptin levels differs between participants who will and will not develop the outcome (dementia). Thus, this potential source of misclassification would likely bias the results toward the null hypothesis of no association between leptin levels and dementia. Our findings are also supported by data on 2871 adults in the Health ABC Study showing a correlation between higher leptin levels and a lower likelihood of decline on global cognitive test scores.2
Lieb W, Seshadri S. Leptin Levels and Alzheimer Disease—Reply. JAMA. 2010;303(15):1478–1479. doi:10.1001/jama.2010.437
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