CMV infection and frailty: Immunologic consequences and disease pathogenesis

Frailty is a common geriatric syndrome that has been variously characterized as a wasting state of decreased physiologic reserve, loss of physiologic complexity, and accumulation of deficits [11, 58, 83], and is an independent risk factor for poor outcomes in older adults [7, 30, 113]. A physiologic phenomenon that has been consistently observed in frail older individuals is a generalized inflammatory state, beyond age-related changes [26, 56, 87, 106]. Frail older adults have higher levels of systemic inflammatory markers, including interleukin-6 and C-reactive protein, than older adults who are not frail, even when chronic diseases are excluded [106]. The chronic activation of inflammatory pathways is known to influence skeletal muscle mass decline, the anemia of chronic disease, hypothalamic-pituitary-adrenal axis (HPA axis) activity, cognition, and a number of chronic disease states, and likely plays an important role in the pathogenesis of frailty through its effects on these multiple physiologic systems [28].