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Davis JC, Guy P, Ashe MC, Liu-Ambrose T, Khan K.Davis JC, et al.J Gerontol A Biol Sci Med Sci. 2007 Aug;62(8):888-91. doi: 10.1093/gerona/62.8.888.J Gerontol A Biol Sci Med Sci. 2007.PMID: 17702881Clinical Trial.