Elevated High Sensitivity C-Reactive Protein and Risk of Abdominal Aortic Aneurysm: A Prospective Population Based Study in The Norwegian HUNT Study.

Objective: Inflammation seems to be crucial in the pathogenesis of abdominal aortic aneurysm (AAA). Previous research links inflammatory biomarkers, such as high sensitivity C-reactive protein (HS-CRP), to AAA. Few studies, however, have used a prospective design. The aim of this study was to examine whether individuals with elevated HS-CRP have increased risk of AAA, using a prospective and population based design.

Methods: This prospective, population based, cohort study included 46 322 participants in the Trøndelag Health Study (HUNT) in Norway (53.7% women). During a median follow up time of 12.6 years (range 0 - 26 years), 407 individuals were diagnosed with AAA (28.8% women). Cox proportional hazard regression was applied to examine associations between HS-CRP and risk of AAA. HS-CRP was treated either as a continuous or a categorical variable (dichotomised at 2 mg/L, 1 mg/L, median (1.2 mg/L), or as quartiles).

Results: The hazard ratio (HR) of developing AAA per 1 mg/L increase in HS-CRP (continuous HS-CRP) was 1.02 (95% CI 1.01 - 1.03) in the analysis adjusted for smoking, coronary heart disease, hypertension, diabetes, body mass index, and total cholesterol. Individuals with HS-CRP 2 mg/L or above had almost twice the risk of AAA compared with individuals with HS-CRP less than 2 mg/L (adjusted HR 1.84; 95% CI 1.51 - 2.25). Dichotomising HS-CRP at a clinical cut off point of 1 mg/L (adjusted HR 2.13, 95% CI 1.64 -2.76), or at the median of 1.2 mg/L (adjusted HR 2.12, 95% CI 1.62 - 2.76), slightly strengthened the HR. The adjusted HR gradually increased through the ordered HS-CRP quartiles, and was almost four times higher (HR 3.87, 95% CI 2.54 - 5.92) in the highest HS-CRP quartile (HS-CRP > 2.7 mg/L) compared with the lowest quartile (HS-CRP ≤ 0.6 mg/L).

Conclusion: Individuals with elevated HS-CRP had significantly increased risk of developing AAA.