The downsides of smoking are plentiful, ranging from stained fingers and teeth to an increased risk of lung cancer. But one potential upside was discovered recently when research suggested that cigarette smoking may delay the onset of Alzheimer's disease. Findings published online this week by the Proceedings of the National Academy of Sciences indicate that nornicotine, a by-product of nicotine, could be responsible for this protective effect.

Kim Janda and Tobin Dickerson of the Scripps Research Institute tested the effect of nornicotine on amyloid beta proteins, which aggregate into the plaques that are a hallmark of Alzheimer's disease. Specifically, the researchers found that a reaction known as glycation, which occurs between the molecule and sugars, alters amyloid proteins so that fewer plaques can form. The authors note that together with nicotine, nornicotine is an intriguing and potentially valuable treatment for Alzheimer's disease. Both compounds are toxic, however, so the scientists suggest investigating new therapies that can mimic their beneficial results without harmful side effects.