Independent association between inflammatory markers (C-reactive protein, interleukin-6, and TNF-α) and essential hypertension

High blood pressure (HBP) has been associated with elevated C-reactive protein (CRP), a marker of chronic mild inflammation. However, the association between HBP and other inflammatory markers, particularly interleukin 6 ( IL-6) and tumour necrosis alpha (TNF-alpha), has not been evaluated in well-controlled studies. We examined the cross-sectional relationship between IL-6, TNF-alpha, and CRP and HBP in a random sample of 196 healthy subjects. All markers were measured in duplicate with high-sensitivity ELISA tests. Three blood pressure ( BP) measurments were averaged for the analysis, and subjects with systolic BP greater than or equal to140 and/or diastolic BP greater than or equal to90 mmHg were considered hypertensive. Log binomial regression was used to estimate multivariate-adjusted prevalence ratios ( PR) of HBP. Of the subjects, 40% (79) were hypertensive ( mean age: 44 years; range 30 - 64). After adjustment for age, sex, body mass index, family history of HBP, and the level of the other inflammatory markers, subjects in the second ( PR: 3.10, P = 0.003), third ( PR: 2.32; P = 0.031), and fourth quartiles ( PR: 2.30; P = 0.036) of IL-6 were more than twice as likely to be hypertensive than those in the first quartile. Corresponding PR estimates for TNF-alpha levels were 1.41 ( P = 0.014) for the second; 1.59 ( P = 0.001) for the third; and 1.61 ( P = 0.025) for the fourth quartile. The CRP - HBP association was not statistically significant. Our results suggest that TNF-alpha and IL-6 could be independent risk factors for HBP in apparently healthy subjects. Nevertheless, the temporal relationship between elevated inflammation markers and HBP should be ascertained in prospective cohort studies.