The age-related increase in low-grade systemic inflammation (Inflammaging) is not driven by cytomegalovirus infection

Abstract

Aging is accompanied by the development of low-grade systemic inflammation, termed 'inflammaging', characterized by raised serum C-reactive protein (CRP) and pro-inflammatory cytokines. Importantly, inflammaging is implicated in the pathogenesis of several of the major age-related diseases including cardiovascular disease, type 2 diabetes, and dementia and is associated with increased mortality. The incidence of infection with the persistent herpes virus cytomegalovirus (CMV) also increases with age. Cross-sectional studies have proposed CMV infection as a significant driver of inflammaging, but a definitive case for CMV as a causative agent in inflammaging has not yet been made. We studied longitudinally 249 subjects (153 men, 96 women) who participated in the Hertfordshire Ageing Study at baseline (1993/5, mean age 67·5 years) and at 10 year follow-up. At both times, anthropometric measurements were made and subjects provided blood samples for analysis of inflammatory status and CMV seropositivity. In the cohort as a whole, serum CRP (P < 0·02) and pro-inflammatory cytokines TNFα (P < 0·001) and IL-6 (P < 0·001) were increased between baseline and follow-up sampling whereas levels of the anti-inflammatory cytokine IL-10 were decreased (P < 0·001). These changes to cytokine status over time occurred equally in the 60% of subjects who were seropositive for CMV at baseline and follow-up, the 8% who were CMV negative at baseline but who became CMV positive by the 10 year follow-up, and also in the 32% who were CMV seronegative throughout. We conclude that CMV infection is not a primary causative factor in the age-related increase in systemic inflammation.