The role of low grade inflammation as measured by C-reactive protein levels in the explanation of socioeconomic differences in carotid atherosclerosis.

Background: The role of inflammation as part of the explanation of socioeconomic differences in carotid atherosclerosis has not been specifically investigated. Methods and Results: The associations between socioeconomic position (SEP), C-reactive protein (CRP), and preclinical carotid atherosclerosis were investigated in a general population sample of 3921 middle-aged Swedish men and women. Common carotid intima-media thickness (IMT) and presence of carotid plaque (focal IMT > 1.2 mm) were determined by B-mode ultrasound. The results showed that low SEP was associated with increased levels of CRP, independently of established risk factors. Furthermore, common carotid IMT increased with increasing CRP-levels. Presence of carotid plaque increased with increasing CRP-levels in men, but not in women. While the socioeconomic differences in carotid IMT were weak, there were associations between low educational level and carotid plaque prevalence with an age- and sex-adjusted odds ratio (OR) of 1.39 (95% Cl: 1.21, 1.59). A similar association was seen for having a manual occupation, OR = 1.23 (95% Cl: 1.07, 1.42). The age- and sex-adjusted absolute differences in carotid plaque prevalence were 9% with regard to educational level and 7% with regard to occupational status. Adjustment for CRP caused only a minor attenuation of the association between SEP and carotid atherosclerosis. Conclusions: The association between SEP and carotid atherosclerosis as measured by carotid IMT and carotid plaque could only to a minor extent be referred to differences in low grade inflammation as measured by CRP.