Predictors of interleukin-6 elevation in older adults

Objectives: To investigate the characteristics of older adults who develop high interleukin-6 (IL-6) levels at 3-year follow-up. Design: Population-based study of adults living in Tuscany, Italy. Setting: Community. Participants: Adults aged 65 and older and were selected for this study. Of 1,155 baseline participants aged 65 and older, 741 had IL-6 measurements at baseline and 3-year follow-up. Measurements: The uppermost quartile of IL-6 was used as the threshold for defining high IL-6 (≥4.18 pg/mL). Serum IL-6 levels were assessed using enzyme immunoassay. Results: Of the 581 participants with IL-6 levels less than 4.18 pg/mL at baseline, 106 (18.2%) had developed high IL-6 at follow-up. Although women had lower IL-6 levels at baseline than men, the risk of developing high IL-6 did not differ according to sex. High adiposity, defined as a body mass index of 30.0 kg/m² or higher (odds ratio (OR)=2.63, 95% confidence interval (CI)=1.40-4.96), and large waist circumference, defined as 102 cm or greater for men and 88 cm or greater for women (OR=2.05, 95% CI=1.24-3.40), were significant predictors of developing high IL-6 at follow-up. Other significant predictors were presence of three or more chronic diseases (OR=3.66, 95% CI=1.54-8.70), higher baseline IL-6 (OR=1.82, 95% CI=1.39-2.38) and higher white blood cell count (OR=1.24, 95% CI=1.06-1.45). Faster walking speed associated with decreased risk of progressing to elevated IL-6 (OR=0.83, 95% CI=0.74-0.92). Conclusion: Older age, greater adiposity, slower walking speed, higher disease burden, and higher white blood cell count were associated with greater risk of IL-6 elevation over a 3-year period. Future research should target older adults with these characteristics to prevent progression to a proinflammatory state.