Nonlinear multisystem physiological dysregulation associated with frailty in older women: implications for etiology and treatment. - Fried LP; Xue QL; Cappola AR; Ferrucci L; Chaves P; Varadhan R; Guralnik JM; Leng SX; Semba RD; Walston JD; Blaum CS; Bandeen-Roche K; et al. (Journals of Gerontology Series A: Biological Sciences & Medical Sciences, 2009)