A clinical trial tested the oral diabetes drug Avandia, which improves insulin sensitivity, against a placebo in 693 people with mild-to-moderate Alzheimer's disease. The drug had no effect on cognition, according to results published online last month in the journal Dementia and Geriatric Cognitive Disorders. (The Food and Drug Administration is currently evaluating whether Avandia should be pulled from the market because it raises the risk for heart attacks and strokes.)
A 2008 study, published in Neurology, tested the effect of insulin itself on the cognitive function of 25 patients with mild dementia. The hormone was administered nasally to aid its entry into the brain, and its use was associated with measurable improvements in attention and memory after three weeks of treatment.