NEW YORK , 19 oct 2008– Low levels of cystatin C -- a blood protein commonly used as a measure of kidney function -- may be a risk factor for the development of Alzheimer's disease in elderly men, researchers report. Cystatin C is produced by nearly all human cells and available in all body fluids. During the past decade, studies have suggested that cystatin C activity in the brain may protect against the development of Alzheimer's disease by inhibiting amyloid-beta -- a protein in the body that forms amyloid plaques in the brain, a key feature of Alzheimer's disease. To further explore this idea, Dr. Johan Sundelof, of Uppsala University, Sweden, and colleagues examined the association between blood levels of cystatin C and the development of Alzheimer's disease in a group of 1,230 men in their early 70s, who were re-assessed when they were about 77 years old. A total of 82 subjects were diagnosed with Alzheimer's disease during follow-up. The researchers observed an association between lower cystatin C levels and higher risk of Alzheimer's disease. According to the researchers, a 0.1-mcmol/L decrease of cystatin C between ages 70 and 77 was associated with a 29 percent higher risk of developing Alzheimer's disease. "Our findings strengthen the evidence of a role for cystatin C in Alzheimer's disease pathogenesis," Sundelof said in an interview with Reuters Health. SOURCE: Neurology, September 30, 2008.