Predictors of interleukin-6 elevation in older adults

To investigate the characteristics of older adults who develop high interleukin-6 (IL-6) levels at 3-year follow-up.

Population-based study of adults living in Tuscany, Italy.

Community.

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.

The uppermost quartile of IL-6 was used as the threshold for defining high IL-6 (> or =4.18 pg/mL). Serum IL-6 levels were assessed using enzyme immunoassay.

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/m(2) 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).

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.