Longitudinal analysis on inflammatory markers and frailty progression: based on the English longitudinal study of aging

Abstract Background: Frailty is a common health state that is closely linked to adverse health outcomes in aging society. Although many inflammatory biomarkers have been cross-sectionally associated with frailty, knowledge on the longitudinal association is still limited. Aims: To investigate the associations of three common inflammatory markers (hypersensitive C-reactive protein [hsCRP], white blood cell [WBC] and fibrinogen) with the progression of frailty. Methods: Data of 2316 participants (age 67.9 ± 6.1 years) were obtained from the English longitudinal study of aging (wave 4, 6 and 8) over an 8-year follow-up. The frailty index (FI) was calculated from 52 items. Mixed-effects models and Cox proportional hazards (Cox-PH) models were used to analyze the associations of hsCRP, WBC and fibrinogen with frailty progression. Values of inflammatory biomarkers were log-transformed. Age, sex and annual income were controlled. Results: Mixed-effects models showed that at a cross-sectional level, higher levels of hsCRP (β: 0.007, 95%CI: 0.004~0.010), WBC (β: 0.021, 95%CI: 0.010~0.032) and fibrinogen (β: 0.022, 95%CI: 0.005~0.038) were associated with greater FI values while no significant time interaction was found. Cox-PH models showed that higher baseline levels of hsCRP (HR: 1.10, 95%CI: 1.03~1.17) and WBC (HR: 1.23, 95%CI: 1.10~1.37) were linked to greater risk of developing frailty within 8 years. Conclusions: We concluded that hsCRP, WBC and fibrinogen can reflect frailty status at a cross-sectional level while only hsCRP and WBC are associated with frailty progression over an 8-year period.