Association of Biomarkers for Inflammation, Endothelial Dysfunction and Oxidative Stress with Cognitive Impairment. The Epidemiology of Hearing Loss Study (EHLS).

BACKGROUND: Individual biomarkers of inflammation, endothelial dysfunction and oxidative stress have been associated with cognitive impairment. This study explored whether a combination of biomarkers could prospectively identify those who developed cognitive decline. METHODS: Biomarkers were obtained during the baseline examination of the Beaver Dam Eye Study (1988-90), and cognitive status was assessed during the 5-year follow-up examination of the Epidemiology of Hearing Loss Study (1998-2000). Cognitive impairment was defined as a score of < 24 points on the Mini-Mental State Examination or self- or proxy report of Alzheimer Disease or dementia. Among those with cognitive data, interleukin-6, isoprostanes, protein carbonyl, soluble inter-cellular adhesion molecule-1 and vascular cell adhesion molecule-1 were available for 950 participants and 2,336 had high sensitivity C-reactive protein. RESULTS: Biomarkers of inflammation and endothelial dysfunction were not associated with cognitive impairment. There was a weak inverse association between higher levels of protein carbonyl content and cognitive impairment (OR, 0.8 per quartile of protein carbonyl content, p=0.045 unadjusted for multiple comparisons). This was not significant on multiple testing and may have been a chance finding. CONCLUSION: We found that many markers of inflammation and endothelial dysfunction were not associated with cognitive impairment. An inverse association with carbonyl protein, a marker of oxidative stress needs further confirmation.