Sniffing insulin? No, it's not diabetics who might partake in this potential treatment, it's Alzheimer's patients. Earlier studies had found a link between lower insulin levels in the brain and Alzheimer's disease, which makes sense since brain cells need insulin to communicate, and the current study built upon this connection.

In the study just over 100 people who had Alzheimer's or mild cognitive impairment (a precursor of the disease) used a nebulizer to squirt insulin up their noses two times a day. Two-thirds of the participants received a dose of insulin, and the other third received placebo. Why this method of delivery, you may be asking? It's because it allows the insulin to go right to the brain, rather than circulating through the rest of the body – in this way, it does not affect blood sugar.

At the end of the four-month study, Suzanne Craft and her team found that people who received insulin did better on tests measuring cognition and memory than people who got the placebo. Specifically, patients who got placebo tended to do about 10% worse on these tests at the end of the study than they had at the beginning, whereas patients who were treated with insulin showed no such decline. Even the patients' caregivers, who were not aware of which treatment the patients were getting at the time, rated the participants' everyday functioning as having improved with the insulin treatment, and declining with placebo.

Some patients also agreed to have a spinal tap to look at proteins in their brains which have been linked to Alzheimer's. Those who had shown improvements in memory function also showed improvements in levels of these proteins and in the way their brains were using glucose, which is the brain's only source of fuel.

More research will be needed to look at the treatment over the long term, but the study adds to a growing body of evidence showing the connection between insulin and cognitive decline.

The study was presented on July 14, 2010 at the International Conference on Alzheimer's Disease in Honolulu. Craft is affiliated with the University of Washington in Seattle.