Study of Nasal Insulin to Fight Forgetfulness - Long-acting Insulin Detemir - 120 Days (SL120)

The study will examine the effects of intranasally administered long-acting insulin detemir on cognition in persons with Alzheimer's disease (AD) or amnestic mild cognitive impairment (aMCI). The rationale for these studies is derived from growing evidence that insulin contributes to multiple brain functions, and that insulin dysregulation can contribute to AD pathogenesis. Thus, therapies aimed at restoring normal insulin signaling in the CNS may have beneficial effects on brain function. Intranasal administration of insulin increases insulin signaling in the brain without raising peripheral levels and causing hypoglycemia. Insulin detemir is an insulin analogue that may have better action in brain than other insulin formulations because of its albumin binding properties. The investigators will test the therapeutic effects of intranasally-administered insulin detemir in a study in which participants will receive insulin detemir, regular insulin, or placebo over a four month period. The investigators will test the hypothesis that insulin and insulin detemir will both improve memory and daily functioning in persons with AD/aMCI compared with placebo, but that insulin detemir will have the greatest effect.