IL-6-independent association of elevated serum neopterin levels with prevalent frailty in community-dwelling older adults

• Published in: Age and ageing 2011-07, Vol.40 (4), p.475-481
• Main Authors: Leng, Sean X., Tian, Xinping, Matteini, Amy, Li, Huifen, Hughes, Jennifer, Jain, Alka, Walston, Jeremy D., Fedarko, Neal S.
• Format: Article
• Language: English
• Subjects: Aged; Aged, 80 and over; Aging - immunology; Analysis of Variance; Baltimore; Biomarkers - blood; Body mass index; Community living; Cross-Sectional Studies; Cytokines; Elder care; Elderly people; Enzyme-Linked Immunosorbent Assay; Frail; Frail Elderly; Geriatrics; Humans; Immune response; Independent Living; Inflammation Mediators - blood; Interleukin-6 - blood; Linear Models; Logistic Models; Neopterin - blood; Odds Ratio; Older people; Research Papers; Risk Assessment; Risk Factors; Serum; Up-Regulation
• ISSN: 0002-0729; 1468-2834
• DOI: 10.1093/ageing/afr047

Background: neopterin is a monocyte/macrophage-derived immune activation marker and its levels increase with age. Frailty is an important clinical syndrome of old age. Previous studies have shown significant association between elevated interleukin-6 (IL-6) levels and frailty. The objective of this study was to evaluate IL-6-independent association of serum neopterin levels with prevalent frailty. Methods: this is a cross-sectional study in community-dwelling older adults recruited from residential and retirement communities in Baltimore, MD, USA. Frailty was determined using validated screening criteria. Serum neopterin and IL-6 levels were measured using standard enzyme-linked immunosorbent assay. Pearson correlation and multivariate linear regression analysis was performed to assess the relationship between log(neopterin) and log(IL-6). Odds ratios (ORs) for frailty were calculated using log(neopterin) and log(IL-6) as continuous measures and across tertiles of neopterin and IL-6 levels, adjusting for age, race, sex, education and body mass index. Results: one hundred and thirty-three individuals with a mean age of 84 years (range 72-97) completed the study. Neopterin levels were significantly higher in frail older adults than those in non-frail controls [median: 8.94 versus 8.35 nM, respectively, P < 0.001 t-test on log(neopterin)]. Log(neopterin) was significantly associated with prevalent frailty, adjusting for log(IL-6). Participants in the top tertile of neopterin had OR of 3.80 [95% confidence interval (CI) = 1.36-10.6, P < 0.01] for frailty. As expected, participants in the top tertile of IL-6 had OR of 3.29 (95% CI = 1.21-7.86, P < 0.05) for frailty. Log(neopterin) correlated with log(IL-6) (correlation coefficient = 0.19, P < 0.05). Moreover, OR for participants in the top neopterin tertile remained significant after adjusting for IL-6 (OR = 3.97, 95% CI = 1.15-13.72, P < 0.05). Conclusion: elevated neopterin levels had IL-6-independent association with prevalent frailty, suggesting potential monocyte/macrophage-mediated immune activation in the frail elderly.