Background: Increased levels of inflammatory proteins have been found in the brains and plasma samples of patients with dementia. Whether the levels of inflammatory proteins in plasma samples are elevated before clinical onset of dementia is unclear.
Objective: To determine whether high levels of inflammatory proteins in plasma samples are associated with an increased risk of dementia.
Design and setting: A case-cohort study within the Rotterdam Study, a population-based prospective cohort study in the Netherlands.
Participants: The source population comprises 6713 subjects who, at baseline (1990-1993), were free of dementia and underwent venipuncture. From these, we selected both a random subcohort of 727 subjects and 188 cases who had developed dementia at follow-up.
Main outcome measures: The associations between plasma levels of alpha1-antichymotrypsin, C-reactive protein, interleukin 6, the soluble forms of intercellular adhesion molecule-1, and vascular cell adhesion molecule-1 and the risk of dementia were examined using the Cox proportional hazards regression models.
Results: High levels of alpha1-antichymotrypsin, interleukin 6, and, to a lesser extent, C-reactive protein were associated with an increased risk of dementia; rate ratios per standard deviation increase were 1.49 (95% confidence interval, 1.23-1.81), 1.28 (95% confidence interval, 1.06-1.55), and 1.12 (95% confidence interval, 0.99-1.25), respectively. Similar associations were observed for Alzheimer disease, whereas rate ratios of vascular dementia were higher for alpha1-antichymotrypsin and C-reactive protein. Soluble forms of intercellular adhesion molecule-1 and vascular cell adhesion molecule-1 were not associated with dementia.
Conclusion: Plasma levels of inflammatory proteins are increased before clinical onset of dementia, Alzheimer disease, and vascular dementia.