Daily intranasal insulin may be effective in slowing progression of mild cognitive impairment (MCI) or Alzheimer’s disease (AD), new research suggests. The findings were presented at the Alzheimer’s Association International Conference (AAIC) 2019.

Investigators found intranasal insulin administered via a novel delivery device slowed the rate of cognitive decline by 1 to 2 years. “The magnitude of the benefit is striking,” study investigator Suzanne Craft, PhD, professor of gerontology and geriatric medicine at Wake Forest School of Medicine in Winston-Salem, North Carolina. The study was first reported by Medscape Medical News.

Insulin is essential for normal functions in the body and brain. It enhances communication between neurons, increases brain blood flow, and protects against beta-amyloid (Aβ) and abnormal tau.

“One of the things I think is very important for memory is that insulin protects the synapses against amyloid, and also generates new synapses. How well insulin works is the best predictor of how successfully one will age,” said Craft.

It appears either patients with AD have low levels of insulin in the brain or the hormone is not working effectively. Boosting insulin levels in the brain might help. However, injecting insulin does not get the hormone straight into the brain, and might lower blood sugar levels, said Craft.

For the study, researchers used a novel mode of delivery — a device that facilitates intranasal applications. The technology involves creating very small aerosol-like droplets of insulin that are driven upwards, directly into the brain and not into the blood stream or lungs, said Craft.

There is growing interest in intranasal delivery of insulin, partly because it is able to penetrate the blood­–brain barrier, she said. The study included 289 patients across 26 sites who had mini-mental state examination (MMSE) scores above 20.