CHICAGO: Swiss researchers said on Monday they have pinpointed a second gene that, when defective, increases the risk of Alzheimer’s disease.

The gene, labelled CYP46, produces a protein that helps the brain process and break down excess cholesterol, which likely plays a role in the buildup of proteins, called beta-amyolids, found to clog the brains of Alzheimer’s victims.

People with mutated forms of both the CYP46 and APOE4 genes have 10 times the risk of developing the disease than those without the mutations. Defective forms of APOE4, which also has a role in processing cholesterol, have previously been shown to increase Alzheimer’s risk.

The study, published in the journal Archives of Neurology, was based on examinations of hundreds of both living and dead patients with and without the disease.

An estimated four million Americans are believed to suffer from Alzheimer’s, which robs victims of memory, the ability to think and language. The risk increases after age 60. Roughly 3 per cent of men and women aged 65 to 74 have Alzheimer’s, with nearly half of those over age 85 afflicted.—Reuters