High interleukin-6 plasma levels are associated with functional impairment in older patients with Vascular dementia

In older individuals, inflammatory mechanisms have been linked to the pathogenesis of both dementia and functional impairment. In this cross-sectional study we have investigated the possible association between some markers of systemic inflammation and functional status, in a sample of one hundred and forty older demented patients including 60 patients with late onset Alzheimer's disease (LOAD) and 80 with vascular dementia (VD). Functional status was evaluated by Barthel Index (BI); the total score ranged from 0 (total dependency) to 20 (total autonomy). Interleukin-1beta, Tumor Necrosis Factor-alpha, Interleukin- 6, Interleukin- 8, and Transforming Grow Factor beta were quantified by ELISA. Among the cytokines evaluated, only IL-6 was correlated with the BI (r: -0.32, p < 0.001). The mean levels of IL-6 progressively decreased from I (9.50 pg/mL), to II (6.40 pg/mL), to III BI tertile (4.80 pg/mL) (p < 0.02). At multiple regression analysis, IL-6 was associated with BI in the whole sample and in VD, but not in LOAD, independent of age, gender, smoking, alcohol consumption, hypertension, diabetes, coronary heart disease, previous stroke, and mini mental state examination score. Our study suggests the existence of an independent and negative relationship between IL-6 plasma levels and functional status in older individuals with vascular dementia. This finding might contribute to explain the 'excess of disability' phenomenon described in older demented patients