Type 2 diabetes mellitus has been associated with an approximately 2-fold increase in risk of Alzheimer's disease (AD). Patients with AD have been reported to have reduced insulin sensitivity, and to have insulin concentrations that are elevated in plasma and decreased in cerebrospinal fluid (CSF). Cognitively normal individuals with insulin resistance are thus of interest in our effort to gain an understanding of the antecedents of this problem. It may be hypothesized that, compared to insulin sensitive subjects otherwise similar in general health and body habitus, insulin resistant subjects are more likely to have CSF indicators of incipient Alzheimer pathology, abnormalities in CSF peptides related to insulin signaling and glucose homeostasis, and possibly other metabolites that are associated with a risk of AD.