Preliminary Evidence of an Association Between an Interleukin 6 Promoter Polymorphism and Self-Reported Attentional Function in Oncology Patients and Their Family Caregivers

Subgroups of individuals may be at greater risk of cytokine-induced changes in attentional function. The purposes of this study were to identify subgroups of individuals with distinct trajectories of attentional function and evaluate for phenotypic and genotypic (i.e., cytokine gene polymorphisms) differences among these subgroups. Self-reported attentional function was evaluated in 252 participants (167 oncology patients and 85 family caregivers) using the Attentional Function Index before radiation therapy and at six additional assessments over 6 months. Three latent classes of attentional function were identified using growth mixture modeling: moderate (36.5%), moderate-to-high (48.0%), and high (15.5%) attentional function. Participants in the moderate class were significantly younger, with more comorbidities and lower functional status, than those in the other two classes. However, only functional status remained significant in multivariable models. Included in the genetic association analyses were 92 single nucleotide polymorphisms (SNPs) among 15 candidate genes. Additive, dominant, and recessive genetic models were assessed for each SNP. Controlling for functional status, only Interleukin 6 (IL6) rs1800795 remained a significant genotypic predictor of class membership in multivariable models. Each additional copy of the rare "G" allele was associated with a 4-fold increase in the odds of belonging to the lower attentional function class (95% confidence interval: [1.78, 8.92]; p = .001). Findings provide preliminary evidence of subgroups of individuals with distinct trajectories of attentional function and of a genetic association with an IL6 promoter polymorphism.