C-reactive protein is not associated with peripheral endothelial function among youth with bipolar disorder

Despite robust associations between bipolar disorder (BD) and cardiovascular risk, there is a paucity of research on the pathologic processes underlying vascular dysfunction in this population. Here, we examine the relationship between peripheral inflammation and microvascular function in youth with BD.

One hundred seventy-seven youth ages 13-20 (n = 93 BD, n = 84 controls) were included. Reactive hyperemia index (RHI), a non-invasive measure of vascular endothelial function, was evaluated using pulse amplitude tonometry. Serum was assayed for C-reactive protein (CRP). We examined differences in CRP based on diagnosis and mood state, and subsequently assessed for the relationship between CRP and RHI in the overall sample and in CRP-by-diagnosis interaction analyses, controlling for age, sex, and body mass index (BMI).

CRP was significantly higher in the BD group (1.94 ± 3.99 mg/L) relative to the controls (0.76 ± 0.86 mg/L; U = 3044, p = 0.01), but this finding did not survive correction for age, sex, and BMI. CRP was not significantly associated with RHI in the overall sample (β = -0.07, p = 0.42), in CRP-by-diagnosis interaction analyses (β = 0.07, p = 0.73), or when controlling for current depression (β = 0.07, p = 0.73) or mania (β = 0.07, p = 0.69).

Unexpectedly, this study found no relationship between CRP and peripheral endothelial function among youth with BD. This may suggest that processes other than inflammation underlie early vascular dysfunction in BD, particularly microvascular dysfunction.