Serum interleukin-6 levels are higher in old age subjects with Alzheimer’s dementia: IL-6, aging and dementia

Elevated interleukin-6 (IL-6) levels have been found positively associated with markers of physical frailty as well as identified as a potential biomarker of Alzheimer’s disease (AD). Thus, we explored the levels of plasma IL-6 at baseline in a cohort of older subjects with or without cognitive impairment, which results may have also implications for coronavirus disease 2019 (COVID-19) clinical management. This is a retrospective study including a cohort of over 60 years old-age subjects, 72 healthy controls, 95 mild cognitive impairment, and 73 AD were included in the study. Plasma IL-6 was measured in all subjects. The sample population included 240 subjects, mostly women with a mean age of 78.61±6.30 (range: 60-93) years. Age significantly correlated with IL-6 plasma levels (r=0.204, P=0.002) even after controlling by gender. No difference was found in body mass index (BMI), nutritional status (assessed by mini nutritional assessment), and comorbidity indices (cumulative illness rating scaleseverity and comorbidity index) among groups. Instead, IL-6 significantly differed, having patients affected by AD higher levels compared to the other groups. Final linear regression analysis showed that independently of age, gender, BMI, nutritional status, number of clinically relevant concomitant diseases, the diagnosis of AD was associated with higher IL-6 plasma levels. These data indicate that serum IL-6 is more elevated in AD, supporting that IL-6 may have also a potential role in response to COVID-19 in old age subjects with cognitive impairment.