An interleukin-18 polymorphism is associated with reduced serum concentrations and better physical functioning in older people

J Gerontol A Biol Sci Med Sci. 2007 Jan;62(1):73-8. doi: 10.1093/gerona/62.1.73.


Background: The proinflammatory cytokine interleukin-18 (IL-18) is associated with major disabling conditions, although whether as byproduct or driver is unclear. The role of common variation in the IL-18 gene on serum concentrations and functioning in old age is unknown.

Methods: We used 1671 participants aged 65-80 years from two studies: the InCHIANTI study and wave 6 of the Iowa-Established Populations for Epidemiological Study of the Elderly (EPESE). We tested three common polymorphisms against IL-18 concentration and measures of functioning.

Results: In the InCHIANTI study, a 1 standard deviation increase in serum IL-18 concentrations was associated with an increased chance of being in the 20% of slowest walkers (odds ratio 1.45; 95% confidence interval, 1.17-1.80; p =.0007) and 20% of those with poorest function based on the Short Physical Performance Battery Score (odds ratio 1.52; 95% confidence interval, 1.22-1.89; p =.00016) in age sex adjusted logistic regression models. There was no association with Activities of Daily Living (p =.26) or Mini-Mental State Examination score (p =.66). The C allele of the IL-18 polymorphism rs5744256 reduced serum concentrations of IL-18 by 39 pmol/mL per allele (p =.00001). The rs5744256 single nucleotide polymorphism was also associated with shorter walk times in InCHIANTI (n = 662, p =.016) and Iowa-EPESE (n = 995, p =.026). In pooled ranked models rs5744256 was also associated with higher SPPB scores (n = 1671, p =.019). Instead of adjusting for confounders in the IL-18 walk time association, we used rs5744256 in a Mendelian randomization analysis: The association remained in instrumental variable models (p =.021).

Conclusion: IL-18 concentrations are associated with physical function in 65- to 80-year-olds. A polymorphism in the IL-18 gene alters IL-18 concentrations and is associated with an improvement in walk speed. IL-18 may play an active role in age-related functional impairment, but these findings need independent replication.

Publication types

  • Multicenter Study
  • Research Support, N.I.H., Extramural
  • Research Support, N.I.H., Intramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Activities of Daily Living
  • Aged
  • Aged, 80 and over
  • Aging / blood*
  • Aging / genetics*
  • Alleles
  • Biomarkers / blood
  • DNA / genetics*
  • Female
  • Follow-Up Studies
  • Genotype
  • Humans
  • Interleukin-18 / blood
  • Interleukin-18 / genetics*
  • Italy
  • Male
  • Motor Activity / physiology*
  • Nucleic Acid Amplification Techniques
  • Polymorphism, Genetic*
  • Retrospective Studies
  • Urban Population


  • Biomarkers
  • Interleukin-18
  • DNA