OBJECTIVES
To investigate long-term variability in serum high sensitivity C-reactive protein (CRP) and interleukin-6 (IL-6) and to determine associated risk factors for high risk inflammatory profiles.
DESIGN
Prospective population-based cohort study.
PARTICIPANTS
Participants (N=1,443) of the Epidemiology of Hearing Loss Study and the Beaver Dam Eye Study, two population-based prospective studies of aging in the same cohort.
MEASUREMENTS
Among participants aged 43–79 years at the initial exam (1988–1990), serum high sensitivity CRP was measured from three time-points (1988–1990, 1998–2000, 2009–2010) and serum IL-6 was measured from two (1998–2000 and 2009–2010).
RESULTS
When IL-6 levels were categorized into tertiles, 50.8% of participants remained in the same group 10 years later (weighted Kappa(κ)=.34). When CRP was categorized into three risk groups, 53.4% of participants remained in the same group during 10 years (κ=.36), and 32.4% remained in the same group at all three examinations (κ=.27). Interleukin 6 increased from a geometric mean of 1.54 pg/L to 1.78 pg/L over 10 years, while CRP increased from a geometric mean of 1.67 mg/L to 2.25 mg/L over 10 years, and then decreased to 1.93 mg/L over the next 10 years. These 10-year decreases in CRP were not observed in those not reporting statin use. Factors associated with long-term higher levels of either IL-6 and CRP included older age (IL-6), obesity, smoking, lower physical activity (IL-6), lower HDL cholesterol (IL-6), and a history of statin (non)use (CRP).
CONCLUSION
Inflammatory marker levels tracked over the long-term into older age with within-person increases observed. Several potentially modifiable risk factors were associated with long-term higher levels of inflammatory markers.