Is very high C-reactive protein in young adults associated with indicators of chronic disease risk?

Cases with very high C-reactive protein (CRP>10mg/L) are often dropped from analytic samples in research on risk for chronic physical and mental illness, but this convention could inadvertently result in excluding those most at risk. We tested whether young adults with very high CRP scored high on indicators of chronic disease risk. We also tested intergenerational pathways to and sex-differentiated correlates of very high CRP.

Data came from Waves I (ages 11-19) and IV (ages 24-34) of the National Longitudinal Study of Adolescent Health (N=13,257). At Wave I, participants' parents reported their own education and health behaviors/health. At Wave IV, young adults reported their socioeconomic status, psychological characteristics, reproductive/health behaviors and health; trained fieldworkers assessed BMI, waist circumference, blood-pressure, and medication use, and collected bloodspots from which high-sensitivity CRP (hs-CRP) was assayed.

Logistic regression analyses revealed that many common indicators of chronic disease risk - including parental health/health behaviors reported 14 years earlier - were associated with very high CRP in young adults. Several of these associations attenuated with the inclusion of BMI. More than 75% of young adults with very high CRP were female. Sex differences in associations of some covariates and very high CRP were observed.

Especially among females, the exclusion of cases with very high CRP could result in an underestimation of "true" associations of CRP with both, chronic disease risk indicators and morbidity/mortality. In many instances, very high CRP could represent an extension of the lower CRP range when it comes to chronic disease risk.