Rosano C, Newman AB, Katz R, Hirsch CH, Kuller LH. Association between lower digit symbol substitution test score and slower gait and greater risk of mortality and of developing incident disability in well-functioning older adults. J Am Geriatr Soc. 2008  ;56(9):1618-25.

Newman AB, Arnold AM, Sachs MC, Ives DG, Cushman M, Strotmeyer ES, Ding J, Kritchevsky SB, Chaves PHM, Fried LP, et al. Long-term function in an older cohort--the cardiovascular health study all stars study. J Am Geriatr Soc. 2009  ;57(3):432-40.