Evidence suggests that a high concentration of C-reactive protein (CRP) is a cardiovascular risk factor and an important correlate of cognitive disorders and depression. Recently, population-based studies examining the association between CRP and stroke, cognitive impairment, or depression have been done but have not yet been systematically reviewed. Here we present a systematic review of the associations between CRP and stroke, cognitive impairment, and depression. Hospital or clinic-based studies were excluded because the inferences might not be easily applicable to the general population. 19 eligible studies of CRP were selected: seven for stroke, six for cognitive disorders, and six for depression. Raised CRP concentrations were associated with history of stroke and increased risk of incident stroke. Meta-analysis of studies with long follow-up (> 8 years) showed that the risk for stroke in healthy individuals with the highest quartile of CRP concentrations increased nearly 70% compared to those with the lowest quartile. High concentrations of CRP were predictive of cognitive decline and dementia. The relations of CRP to depression were all cross-sectional and were not consistent. We conclude that high concentrations of CRP are associated with increased risk of stroke and cognitive impairment. The association between CRP and depression should be studied prospectively.
