• Changes in cognition [ Time Frame: every 8 weeks for 16 weeks, again at 8 weeks post-treatment (24 weeks) ] [ Designated as safety issue: No ]
  
• glucose metabolism [ Time Frame: every 8 weeks for 16 weeks, again at 8 weeks post-treatment (24 weeks) ] [ Designated as safety issue: No ]
  
• plasma biological markers [ Time Frame: every 8 weeks for 16 weeks, again at 8 weeks post-treatment (24 weeks) ] [ Designated as safety issue: No ]
  

• CSF biological markers [ Time Frame: every 8 weeks for 16 weeks, again at 8 weeks post-treatment (24 weeks) ] [ Designated as safety issue: No ]
  
• cerebral glucose metabolism [ Time Frame: every 8 weeks for 16 weeks, again at 8 weeks post-treatment (24 weeks) ] [ Designated as safety issue: No ]
  

A growing body of evidence suggests that insulin plays a role in normal memory processes and that insulin abnormalities may contribute to cognitive and brain changes associated with Alzheimer's disease (AD). Interestingly, insulin administered to the nasal cavity is transported within a few minutes into the brain, but does not affect blood sugar or insulin levels.

This study will consist of a randomized double-blind, placebo-controlled parallel group trial in which 90 participants with AD or MCI receive daily intranasal administrations of either insulin (10 or 20 IU twice a day for a total dose of 20 or 40 IU per day) or placebo (saline twice a day) for 4 months. The study will examine the effects of intranasal insulin administration on cognition, cerebral glucose metabolism, and β-amyloid (Aβ) in cerebrospinal fluid (CSF) and plasma, testing the hypothesis that daily intranasal insulin administration for 4 months will facilitate memory for adults with AD, and adults with mild cognitive impairment (MCI). A subset of participants will have the option to participate in 2 sub-studies: PET scans (prior to and at the end of treatment) to determine whether intranasal insulin increases cerebral glucose metabolism; lumbar punctures (LPs) before and at the end of treatment to determine effects of intranasal insulin administration on CSF Aβ levels.

Inclusion Criteria:

• Age 55 or greater
• Good physical health
• Memory impairment with a diagnosis of mild cognitive impairment (MCI) or Alzheimer's disease (AD)
• Participants on stable doses of Memantine (Namenda) or cholinesterase inhibitors will be eligible

Exclusion Criteria:

• Chronic sinus problems/allergies with chronic use of nasal decongestants or antihistamines
• Significant neurologic disease that might affect cognition (other than AD), such as stroke, Parkinson's disease, multiple sclerosis, severe head injury with loss of consciousness for more than 30 minutes or with permanent neurologic symptoms
• Significant medical illness or organ failure, such as uncontrolled hypertension or cardiovascular disease, chronic obstructive pulmonary disease, liver disease, or kidney disease
• Preexisting diabetes or current or previous use of hypoglycemic agents or insulin; participants will be excluded if they have a fasting blood sugar greater than 165 on baseline OGTT
• Clinically significant elevations in liver function tests, cholesterol, or triglycerides
• Major psychiatric disorders (e.g., untreated major depression and schizophrenia)
• Chronic use of the following types of medications: anti-psychotic, anxiolytic, and opiates