Insulin Nasal Spray Shows Promise for Alzheimer’s Disease

A small clinical trial has found that daily doses of an insulin nasal spray can slow memory loss and preserve thinking skills in people with mild to moderate Alzheimer’s disease. A larger study is needed, though, to confirm the effectiveness of this therapy.

Photo of an older woman caring for her husband.

Alzheimer’s disease is a complex, irreversible brain disease that slowly destroys memory and thinking skills. Symptoms usually begin to appear after age 60. Although the cause of Alzheimer’s disease is unknown, researchers suspect that genes, metabolism, environment and lifestyle factors all play a role.

Over the past decade, some scientists have found evidence that abnormal functioning of the hormone insulin might contribute to memory loss and Alzheimer’s disease. Insulin helps to convert blood sugar, or glucose, into energy, and it’s known to be important to normal brain functioning.

Dr. Suzanne Craft of the Veterans Affairs Puget Sound Health Care System and her colleagues have been working to see if restoring normal insulin function to the brain might provide cognitive benefits and slow the progression of Alzheimer’s disease. Their research is supported in part by NIH’s National Institute on Aging (NIA) and the U.S. Department of Veterans Affairs.

Their new study examined the effects of an insulin nasal spray on 104 people with mild to moderate Alzheimer’s disease or mild cognitive impairment, a condition marked by memory problems that may eventually progress to Alzheimer’s disease. The nasal spray was designed to deliver insulin quickly and directly to the brain without causing harmful changes to blood insulin or glucose levels throughout the body.

Participants were randomly assigned to receive daily doses of either 20 IU (international units) of insulin, 40 IU of insulin or a saline placebo administered through a nasal drug delivery device. Memory, cognition and functional ability were measured before and after the 4-month treatment period.

As reported in the September 12, 2011, online edition of the Archives of Neurology, the researchers found that both doses of insulin preserved general functional abilities, or activities of daily living, as assessed by caregivers. In addition, treatment with 20 IU of intranasal insulin led to improved memory. However, no memory improvement was seen in the placebo group or in those receiving 40 IU of insulin, which suggests that this dose may exceed the optimal dose for memory. No harmful side effects were observed in the insulin-treated groups.

“The results are very promising. Not only did we see improved memory in one group, but there also seemed to be improved general functioning in both groups receiving insulin,” says Dr. Laurie Ryan, who oversees Alzheimer’s disease clinical trials supported by NIA. “Still, it’s important to remember that this research is still in its early stages. The findings highlight the need for a larger study, with more patients and a longer duration of treatment, to take a definitive look at whether or not this treatment will be effective.”