MONDAY, Sept. 12 (HealthDay News) -- A nasal insulin spray may someday help people with mild memory problems or early Alzheimer's disease improve or preserve their mental functioning, a new small study suggests.

But, the study authors added, much more research is needed to see if the therapy will actually benefit patients.

Alzheimer's disease, the most common form of dementia in the elderly, initially causes difficulty with thought, memory and language, and insulin dysfunction is thought to play a role in symptoms.

"Although a small study, the authors provide some of the most convincing evidence to date that insulin treatment may alleviate symptoms of Alzheimer's disease," said Dr. James E. Galvin, professor of neurology and psychiatry and director of the Pearl S. Barlow Center for Memory Evaluation and Treatment at NYU Langone Medical Center.

Previous studies have suggested a link between obesity, type 2 diabetes and Alzheimer's disease, Galvin said. This study "further supports links between impaired insulin signaling in the brain and cognitive decline," he added.

For the four-month study, published online Sept. 12 in Archives of Neurology, Seattle researchers recruited 104 people with mild memory problems related to Alzheimer's disease or a condition known as amnestic mild cognitive impairment (aMCI). Thirty-six participants received 20 IU (international units) of insulin daily, 38 participants got 40 IUs of insulin daily, and 30 took a placebo daily.

The researchers assessed the insulin's effects on thought processes, everyday functioning and glucose metabolism in the brain, among other factors.

At the end of the study period, those who took 20 IUs daily demonstrated improved story recall -- they could better remember details immediately after hearing a story and after a brief lapse in time. Neither those taking the higher dose of insulin nor those taking the placebo showed improved story recall.

Also, results of a standard dementia test taken before and after the study showed no declines for either insulin group compared to the placebo takers.

The study authors also found that participants with Alzheimer's who got either dose of insulin had preserved function compared with people taking the placebo. The placebo group showed slight declines overall.

"The results of our pilot trial demonstrate that the administration of intranasal insulin stabilized or improved cognition, function and cerebral glucose metabolism for adults with aMCI or AD [Alzheimer's disease]," Suzanne Craft, of the Veterans Affairs Puget Sound Health Care System and the University of Washington School of Medicine, and colleagues said in a journal news release.

More research is needed to see if insulin therapy can be recommended for staving off the symptoms of Alzheimer's, but the researchers are optimistic about the findings.

"Taken together, these results provide an impetus for future clinical trials of intranasal insulin therapy and for further mechanistic studies of insulin's role in the pathogenesis of AD," they wrote.

Dr. Sam Gandy, professor of neurology and psychiatry and director of the Center for Cognitive Health at Mount Sinai Alzheimer's Disease Research Center in New York City, said the findings may lead to new avenues for treatment.

"Although this was considered to be an unconventional approach, the building basic science underpinnings now provide a clear plausible pathway to totally novel therapies for AD," Gandy said.

Insulin in the brain functions differently than in the rest of the body, he said, "so this story may be about the brain-specific role of insulin signaling and not necessarily about insulin's role in glucose uptake."

Trials are under way assessing insulin sensitizers such as metformin for Alzheimer's disease, Gandy noted. "This clinical success and these new basic data provide optimism that insulin sensitizers may well have benefit in AD," he said.

The study was supported by the U.S. National Institutes of Health.

More information

For more on Alzheimer's disease, visit the U.S. National Institute on Aging.