Interleukin-6 covaries inversely with cognitive performance among middle-aged community volunteers

Objective: Recent evidence suggests that higher peripheral levels of interleukin 6 (IL-6) are associated with poorer cognitive function and predict future cognitive decline among the elderly. The current investigation extends the study of relationships between plasma IL-6 and cognitive performance to healthy middle-aged adults and to an examination of more specific cognitive domains. Methods: Five hundred relatively healthy community volunteers aged 30 to 54 bad blood drawn for the determination of plasma IL-6 levels and completed a battery of neuropsychological tests evaluating memory and executive function. Results: After controlling for age, gender, race, and education, hierarchical regression analyses revealed an inverse relationship between circulating levels of IL-6 and performance on clusters of tests assessing auditory recognition memory, attention/working memory, and executive function. In contrast, there was no association between IL-6 and performance on tests of general memory. Secondary analyses demonstrated that relationships between IL-6 and auditory recognition and working memory and executive function were independent of a number of health factors, including body mass index, smoking, and hypertension. Conclusions: These findings contribute to a growing body of evidence linking chronic inflammation to poorer cognitive functioning and extend these findings to a midlife community sample, raising the possibility that IL-6 may represent a biomarker for risk of future cognitive decline.