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Crowe M, Clay OJ, Martin RC, Howard VJ, Wadley VG, Sawyer P, Allman RM.Crowe M, et al.J Gerontol A Biol Sci Med Sci. 2013 Feb;68(2):198-204. doi: 10.1093/gerona/gls122. Epub 2012 Apr 30.J Gerontol A Biol Sci Med Sci. 2013.PMID: 22546959Free PMC article.