Relationship of Obesity with C-Reactive Protein and Interleukin-6 in Women
Background: C-reactive protein (CRP) and interleukin-6 (IL6) have been associated with increased risk of cardiovascular disease (CVD). Adipocytes produce IL6, the chief determinant of hepatic CRP production. The purpose of this study was to examine the relationship between obesity and CRP and IL6 levels. Methods: We analyzed the relationship between obesity, elevated high sensitivity CRP (HS-CRP) levels (75th percentile: >0.54 mg/dl) and elevated IL6 levels (75th percentile: >2.04 pg/ml) among a sample of 328 women in the Women’s Health Study. The women in our analyses were age 45-84 years, free from pre-existing CVD or cancer at baseline and had complete covariate information. Results: Overweight (body mass index [BMI] 25-<30 kg/m 2 ) and obese (BMI ≥30 kg/m 2 ) women were significantly more likely to have elevated HS-CRP and IL6 levels than women with a normal BMI (<25 kg/m 2 ). After adjustment for age, smoking, parental history of myocardial infarction, current use of hormone replacement therapy (HRT), menopausal status, physical activity, history of diabetes, hypertension, and elevated cholesterol, the odds ratios (OR) for elevated HS-CRP were 2.97 (95%CI, 1.61-5.50) for overweight women and 6.18 (95%CI, 2.82-13.56) for obese women. In multivariate models, the OR’s for elevated IL6 were 1.72 (95%CI, 0.90-3.27) for overweight women and 4.78 (95%CI, 2.18-10.47) for obese women. Since IL6 levels are highly correlated with CRP levels, adjusting for IL6 attenuated the relationship between obesity and elevated HS-CRP, such that the multivariate IL6-adjusted OR’s for elevated HS-CRP were 2.46 (95%CI, 1.28-4.75) and 4.43 (95% CI, 1.89-10.35) for overweight and obese women, respectively. Because HRT use is associated with higher CRP levels and generally lower BMI, we also examined the effects among the subgroup of postmenopausal women not currently using HRT. Results remained highly significant in this subgroup of women. Conclusion: Overweight and obese women are at substantially increased risk of having elevated CRP and IL6 levels. CRP remained independently associated with obesity, even after controlling for IL6.