The exact association of blood YKL-40 and AD needs further study as prospective analyses in cognitively unimpaired individuals suggest higher levels may be potentially protective (with reduced Aβ accumulation and improved cognitive testing) [142], while other studies suggest YKL-40 as a detrimental marker [143,144] and possibly specific to certain ethnic groups [145]. This evidence concerns the gene CHI3L1 and Alzheimer disease.