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Inverse U-Shaped Link Between CRP, Systolic BP in RA

Arthritis Res Ther; 2018 Jun 1; Yu, Kim, Vanni, et al

Across a broad range of C-reactive protein (CRP) observed in rheumatoid arthritis (RA) and non-RA outpatients, researchers found an inverse U-shaped relationship between CRP and systolic blood pressure (SBP), highlighting a relationship not previously observed when studying the general population. They studied subjects from a tertiary care outpatient population with CRP and BP measured on the same date in 2009–2010; RA outpatients were identified using a validated algorithm. General population data were obtained from the National Health and Nutrition Examination Survey (NHANES) as comparison. They found:

  • Of 24,325 subjects from the outpatient population, 1,811 had RA, and 5,561 were from NHANES.
  • In RA outpatients, a positive relationship was observed between CRP and SBP at CRP < 6 mg/L and an inverse association at CRP ≥ 6 mg/L.
  • A similar inverse U-shaped relationship was observed in non-RA outpatients.
  • In NHANES, a positive relationship was observed between CRP and SBP as demonstrated by previous studies.
  • Longitudinal analysis in RA showed that every 10 mg/L increase in CRP was associated with a 0.38 mmHg reduction in SBP.
Citation:

Yu Z, Kim SC, Vanni K, et al. Association between inflammation and systolic blood pressure in RA compared to patients without RA. Arthritis Res Ther. 2018;20:107. doi:10.1186/s13075-018-1597-9.

Commentary:

Cardiovascular (CV) risk is increased in RA, and has been attributed to inflammation. Furthermore, increased CV risk with non-steroidal anti-inflammatory drugs (NSAIDs) has been attributed to these drugs’ effect on blood pressure. Using C-reactive protein (CRP) concentrations as a proxy for inflammation, this study examined the interactions of CRP and systolic blood pressure (SBP) in 3 populations. In NHANES, general population increases in CRP were associated with increases in SBP. Similarly, in patients with RA, a positive relationship was observed between CRP and SBP at CRP < 6 mg/L and an inverse association at CRP ≥ 6 mg/L. A similar inverse U-shaped relationship was observed in patients without RA. However, when RA patients had an increase in CRP of >10 mg/L, SBP decreased by 0.38 mm of mercury. The clinical significance of these findings is not clear, however. In conclusion, this study indicates the complexity of the relationships between inflammation, blood pressure, and CV risk, but does not suggest any changes in clinical management.—Harold E. Paulus, M.D.; Emeritus Professor; University of California, Los Angeles; Division of Rheumatology.

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