Elevated C-reactive protein levels are associated with prevalent dementia in the oldest-old

C-reactive protein (CRP) is a nonspecific marker of inflammation that is increased in the brain and serum of patients with Alzheimer's disease (AD), and has been associated with increased risk of developing dementia. Inflammation increases with age, and the number of people reaching age 90 years and older is growing, making the association between inflammation and dementia increasingly relevant. Using a cross-sectional design, we examined whether high levels of serum CRP are associated with increased odds of prevalent dementia in the oldest-old.

Serum CRP levels of 305 participants (mean age +/- standard deviation, 94.3 +/- 2.9 years) from the 90+ Study, a longitudinal cohort study of people aged 90 years and older, were evaluated with respect to all-cause dementia. Levels of CRP were divided into three categories: undetectable (<0.5 mg/dL), detectable (0.5-0.7 mg/dL), and elevated (> or =0.8 mg/dL). Odds ratios (ORs) were calculated using logistic regression, and were adjusted for covariates.

Relative to participants with undetectable CRP levels, participants with detectable or elevated CRP levels had increased odds of all-cause dementia (detectable: OR, 3.0; 95% confidence interval, 1.2-7.3; elevated: OR, 5.0; 95% confidence interval, 1.9-12.9). When participants were subdivided by gender, significantly increased ORs were seen only in women.

In the oldest-old, high CRP levels are associated with increased odds of all-cause dementia, particularly in women. Prospective studies are necessary to confirm whether increased CRP levels are associated with an increased risk of developing dementia in this age group.