Inflammatory markers and frailty

As the aging population increases rapidly worldwide, caring for frail older adults has become the mandate of modern medicine. As such, frailty has been increasingly recognized as an important geriatric syndrome. This is further supported by the recent development of an operational definition, validation of a set of criteria, and evidence for its syndromic nature. Frailty is characterized by decreased functional and physiologic reserve, increased vulnerability to stressors, as well as high risk for serious adverse health outcomes including disability, dependency, and mortality. Although the pathogenesis of this syndrome is far from being elucidated, frail older adults demonstrate dysregulations in multiple physiologic systems. As discussed elsewhere in this handbook, low grade, chronic systemic inflammation manifested in older adults, so-called inflamm-aging, is an important feature of immunosenescence. Activation of the inflammation system marked by elevated levels of inflammatory markers, above and beyond age-related increases, is considered the most prominent pathophysiological feature of frailty. This chapter provides an overview of the syndrome of frailty and its relationship with several molecular and cellular inflammatory markers, including interleukin-6 (IL-6), C-reactive protein (CRP), and white blood cell (WBC) and its specific subpopulations. It also discusses the potential role of chronic systemic inflammation, directly and/or through other intermediary systems, in the pathogenesis of frailty.