Interleukin-1 receptor antagonist, interleukin-6, and C-reactive protein as predictors of mortality in nonagenarians: The vitality 90+ study

Abstract

Background. Inflammation plays a major role in both aging and chronic disease. Longitudinal studies in very old people can improve our understanding of these processes. We investigated blood levels of C-reactive protein (CRP), interleukin-6 (IL-6), interleukin-1 receptor antagonist (IL-1ra), and their combinations as predictors of mortality in nonagenarians. Methods. This is a prospective population-based study including both community-dwelling and institutionalized nonagenarians enrolled in the Vitality 90+ Study. Altogether 285 persons participated in the baseline interview and gave blood. Information on chronic disease was drawn from health center registers. Data on mortality over 4 years were obtained from the Population Register Center. In Cox proportional hazards models, chronic disease and major risk factors were adjusted for. Results. Plasma levels of IL-1ra, IL-6, and CRP were higher in persons who died during the follow-up than in those who survived. When sex, education, cardiovascular disease, diabetes, cancer, history of infections, high density lipoprotein cholesterol, Mini-Mental State Examination, body mass index, smoking status, and exercise were adjusted for, only IL-1ra was a significant predictor of mortality (hazard ratio [HR] 2.12; 95% confidence interval [CI], 1.24-3.62). Persons in the upper tertiles of both CRP and IL-1ra (HR 2.72; 95% CI, 1.25-6.00), or in the upper tertile of all three markers (HR 2.34; 95% CI, 1.23-4.61), had higher mortality than those who were not in the upper tertile in any of the markers. Conclusions. IL-1ra is a powerful prognostic marker in very old people. Our results implicate its role in the complex interaction between inflammatory markers in aging and disease. Copyright 2007 by The Gerontological Society of America.