In a four-month study, patients with Alzheimer's and mild cognitive impairment treated with a lower dose of an insulin nasal spray tended to score better on memory tests than patients who were not treated with insulin.
At the higher insulin dose given, patients showed improvement in daily functioning, compared to patients treated with a placebo spray, but no difference was seen in cognition.
The study included just over 100 patients, but researchers are in the planning stages of a larger and longer intranasal insulin study in patients with Alzheimer's disease and mild cognitive impairment, which often progresses to Alzheimer's.
The pilot study was reported in Honolulu at the International Conference on Alzheimer's Disease 2010.
"Four months is rather short for a treatment study," study researcher Suzanne Craft, PhD, of the Veteran's Administration Puget Sound, tells WebMD. "But if longer studies show this to be a safe and beneficial treatment, I could see it being something that patients might want to try."
The Brain Needs Insulin
Craft first began studying the impact of insulin on memory more than a decade ago.
She explains that brain cells use sugar for energy, but the brain cannot make insulin or store it. The efficiency of getting energy from the rest of the body to the brain is a critical component of the brain's ability to function.
It is now recognized that patients with Alzheimer's disease have reduced brain-insulin signaling as well as lower levels of insulin in the spinal fluid.
Craft and colleagues hypothesized that restoring normal insulin function to the brain might benefit patients with memory declines.
In the newly reported study, 109 patients with Alzheimer's disease or mild cognitive impairment were treated with either 20 international units (IU) or 40 IU of intranasal insulin daily or placebo.
Over the next four months, most placebo-treated patients showed declines in cognitive functioning, while most insulin-treated patients did not, Craft says.
Few side effects other than runny nose and occasional feelings of lightheadedness were reported in the insulin-treated patients.
The researchers also conducted lumbar punctures on 23 patients at the beginning of the study and following treatment to look for abnormal proteins associated with Alzheimer's disease in the spinal fluid.
They found lower levels of some of these proteins in the fluid of insulin-treated patients who also had improved memory and functional status scores.
Alzheimer's Association Chief Medical and Scientific Officer William Thies, PhD, calls the early work interesting, but he adds that much more research is needed to establish the safety and effectiveness of the approach.
"I don't know that intranasal insulin will ever become a practical treatment for large numbers of people," he says. "The value of this research may be in identifying a new pathway for potential treatments."
Thies adds that new treatments are urgently needed.
"There is a lot of Alzheimer's disease now, and there is going to be a lot more by the middle of this century," he says. "If we don't find better ways of dealing with this disease it will bankrupt our health care system."