C-reactive protein, inflammatory conditions, and cardiovascular disease risk

It is uncertain to what extent high C-reactive protein (CRP) concentrations reflect the presence of inflammatory conditions in the community.

We evaluated 3782 Framingham Offspring Study participants (mean age 55 years; 52% women) free of baseline cardiovascular disease. Logistic regression models examined the prevalence of common inflammatory conditions by CRP categories, while a separate matched case-referent analysis evaluated the prevalence of uncommon inflammatory conditions. Cox models were used to assess the influence of common inflammatory conditions on relations between CRP and incident cardiovascular disease.

Common inflammatory conditions were reported by nearly half of the participants; these individuals were more likely to have markedly high CRP concentrations (>10 mg/L, P for trend=.001). In multivariable models, there were increased odds of having at least one common inflammatory condition with CRP concentrations of 1-3.0, 3.01-10, and >10 mg/L, compared with the referent category (<1 mg/L); the respective odds ratios with 95% confidence intervals were 1.41 (1.07-1.86), 1.45 (1.07-1.98), and 1.64 (1.09-2.47) in men, and 1.08 (0.82-1.43), 1.07 (0.80-1.44), and 1.38 (0.97-1.96) in women. In case-referent analyses, uncommon inflammatory conditions were more common in individuals with CRP >10 mg/L compared with those with CRP <1 mg/L (12.1% vs 6.6%; P=.0001). In multivariable models, higher CRP categories were not associated with incident cardiovascular disease, and with additional adjustment for inflammatory conditions, results remained unchanged.

There is high prevalence of common and uncommon inflammatory conditions in individuals with high CRP concentrations. Higher CRP concentrations should be interpreted with caution in cardiovascular disease risk assessment.