The combined association of depressive symptoms and C-reactive protein for incident disease risk up to 12 years later. Findings from the English Longitudinal Study of Ageing (ELSA)

Depression and inflammation are interrelated, and both are associated with the development of long-term conditions (LTCs). We investigated whether the combination of elevated depressive symptoms and elevated C-reactive protein (CRP) was associated with the rate of onset of a range of LTCs.We analysed data from 5360 participants (65.77 ± 9.46 years; 54.1% female) from the English Longitudinal Study of Ageing (ELSA). Depressive symptoms were indicated using the Centre for Epidemiological Studies Depression (CES-D) scale and scores were combined with high sensitivity (hs)-CRP values to reflect the additive interaction between low/high depressive symptoms (CES-D ≥4) and low/high CRP (>3mg/L). Participants were followed-up for up to 12 years to predict incident illness. Cox proportional hazard regression was used controlling for covariates.In fully adjusted models, the combination of elevated depressive symptoms and elevated CRP was an independent predictor of coronary heart disease (CHD) (HR = 1.68, 95% C.I. = 1.01-2.78), stroke (HR = 2.02; 95% C.I. = 1.48-2.76), diabetes/high blood glucose (HR = 1.69; 95% C.I. = 1.11-2.57), and pulmonary disease (HR = 1.79; 95% C.I. = 1.02-3.15) relative to low depressive symptoms/low CRP, independently of age, sex, wealth, cohabitation, smoking status, body mass index and hypertension. Elevated depressive symptoms and low CRP was associated with arthritis incidence (HR = 1.49; 95% C.I. = 1.15-1.92). No association was found for cancer incidence.A combination of depressive symptoms and CRP was implicated in the onset of CHD, stroke, diabetes/high blood glucose, and pulmonary disease up to 12 years later, reflecting the role of psychobiological processes across multiple disease states.