Association between baseline kidney function and change in CRP: an analysis of the cardiovascular health study.

Background: In cross-sectional analyses, C-reactive protein (CRP) levels are inversely related to levels of kidney function. The relationship between kidney function and subsequent changes in CRP is unknown.

Methods: We studied 4,364 individuals from the Cardiovascular Health Study, a longitudinal cohort of community-dwelling older adults. Baseline eGFRcys was estimated using cystatin C. CRP was measured at baseline and after 3 and 7 years of follow-up; slopes of change in CRP were calculated.

Results: The mean (SD) age of the cohort was 72 (5.2) years; mean (SD) eGFRcys was 78.9 (18.4) ml/min/1.73 m(2). The median (interquartile range IQR) baseline CRP was 2.39 (1.22, 4.33) mg/l; the median (IQR) yearly change in CRP was -0.0051 (-0.020 to 0.27) mg/l/year. After adjustment for demographic characteristics and the initial level of CRP, each standard deviation lower baseline eGFR was associated with a small and non-significant yearly increase in CRP (0.032 mg/l/year; 95% CI: -0.005 to 0.070, p = 0.094).

Conclusions: We did not find a relationship between eGFR and subsequent changes in CRP. The association between kidney function and CRP in cross-sectional analyses may reflect unmeasured confounding by atherosclerosis; alternatively, the burden of comorbidity and interval mortality in this population may have masked a stronger longitudinal association between kidney function and change in CRP. Further study in younger populations may clarify whether impaired kidney function leads to change in inflammation over time.