Proposed by Nagi(43), the pathway begins with a disease process that causes organ pathology. As this pathology becomes clinically relevant, organ dysfunction emerges, termed impairment. Impairment, in turn, leads to reductions in actions, termed functional limitations. Functional limitations may then lead to disability, defined as difficulty performing activities in daily life. Disability is an upstream precursor to and determinant of both health-related quality of life (HRQL) and mortality.