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To the Editor We read the article by Willette et al1 with interest. The findings of this study are important because insulin resistance is a growing health problem, and measures to decrease the incidence of Alzheimer disease (AD) are urgently needed. However, we have some comments on this well-designed and well-performed study.
First, checking fasting glucose levels only once may be insufficient to diagnose or exclude diabetes mellitus (DM). For an accurate diagnosis of DM, fasting glucose levels of 126 mg/dL or greater on 2 occasions (to convert to millimoles per liter, multiply by 0.0555), a glycated hemoglobin level of 6.5% or greater (to convert to proportion of total hemoglobin, multiply by 0.01), a random blood glucose level of 200 mg/dL or greater with accompanying symptoms, or a second-hour blood glucose level at 75-g oral glucose tolerance test of 200 mg/dL or greater are needed. Older adults with DM, especially, may have normal fasting blood glucose levels.2 To draw more accurate conclusions regarding the association of insulin resistance and AD, measuring postprandial glucose levels and/or glycated hemoglobin levels would prove beneficial.
Muratli S, Soyluk O, Tufan F. Confounders Regarding the Association of Insulin Resistance and Alzheimer Disease. JAMA Neurol. 2016;73(2):239-240. doi:10.1001/jamaneurol.2015.3983