In the years following the terrorist attacks of 9/11/2001, efforts have been made to monitor the health of rescue and recovery workers involved in the emergency response and subsequent cleanup efforts. A cohort ofWTC 9/11 general (nonfirefighter) responders (the General Responder Cohort (GRC)) has been established. As this cohort ages, characterization of the changes in health patterns due to aging is becoming increasingly important. The dynamics of the aging process vary considerably across individuals in any population, which is relevant to understanding anticipated changes in physical health and cognitive functioning [1–۳]. Evidence of this heterogeneity can be observed from the molecular/cellular level (via telomere dynamics, DNA methylation patterns, etc.) up to the macroscopic level (frailty, mortality, etc.) [4]. The aim of this study was to evaluate age-related deterioration in physiological functions using the clinical construct of frailty [5]. Frailty is a physical state characterized by increased vulnerability to adverse health outcomes and is believed to arise from diminishing physiological reserve and gradual loss of the body’s ability to maintain homeostatic equilibrium [6]. It has become recognized as a standard geriatric syndrome [7] and there have been increased calls for including frailty assessment as a part of routine clinical encounters [8]. Since 2002, the World Trade Center Health program (WTCHP) has enrolled responders and conducted clinical and health monitoring on this cohort (which continues to increase) [9]. Frailty screening/assessment has not been part of these health evaluations, but the clinical data collected on this cohort contains elements that can be used to measure frailty. Due to its clinically complex profile, no consensus definition of frailty currently exists. In this study, we adopted one popular approach, introduced by Mitnitski et al. (2001) [10], which conceptualizes frailty as the accumulation of functional and health deficits resulting from (and indicative of) a diminishing ability to maintain normal function/homeostasis [11]. With this “deficit accumulation” model, frailty is measured by computing the proportion of considered deficits present in an individual [12].