To explore the relationships between C-reactive protein (CRP), metabolic syndrome (MetS) and incidence of severe knee or hip osteoarthritis (OA) in a prospective study.
A population-based cohort (n=5171, mean age 57.5+/-5.9 years) was examined between 1991 and 1994. Data was collected on lifestyle habits, measures of overweight, blood pressure as well as high-density lipoprotein (HDL) cholesterol, triglycerides, glucose and CRP measured with high-sensitive methods. Incidence of severe OA, defined as arthroplasty due to knee or hip OA, was monitored over 12 years of follow-up, in relation to CRP levels and presence of the MetS according to the adult treatment panel III-national cholesterol education program (ATPIII-NCEP) definition.
A total of 120 participants had severe hip OA and 89 had knee OA during the follow-up. After adjustment for age, sex, smoking, physical activity and CRP, presence of MetS was associated with significantly increased risk of knee OA (relative risk [RR]: 2.1, 95% confidence interval [CI]: 1.3-3.3). However, this relationship was attenuated and non-significant after adjustment for body mass index (BMI) (RR: 1.1, 95% CI: 0.7-1.8). MetS was not significantly associated with incidence of hip OA. In women, CRP was associated with knee OA in the age-adjusted analysis. However, there was no significant relationship between CRP and incidence of knee or hip OA after risk factor adjustments.
The increased incidence of knee OA in participants with the MetS was largely explained by increased BMI. CRP was not associated with incidence of knee or hip OA when possible confounding factors were taken into account.