The role of preclinical atherosclerosis in the explanation of educational differences in incidence of coronary events

Abstract

The associations between educational level, preclinical carotid atherosclerosis and incident coronary events (CE), were investigated in a general population sample of 5399 Swedish middle-aged men and women without history of cardiovascular disease (CVD) over a median follow-up of 8.7 years. Presence of carotid plaque (focal intima-media thickness (IMT) >1.2 mm) was determined by B-mode ultrasound. In the age- and sex-adjusted model, there was an inverse relationship between educational level and risk of future CE (p for trend = 0.002). To explore if there were education differences between groups with similar degrees of preclinical carotid atherosclerosis stratified analyses were made. Those with low educational level without carotid plaque showed a slightly increased hazard rate ratio (HRR), 1.14 (95% CI: 0.65, 1.97), compared to those with high educational level without carotid plaque (reference group). For those with high educational level with carotid plaque the HRR was 1.53 (95% CI: 0.92, 2.55). Having both low educational level and carotid plaque was associated with a HRR of 2.72 (95% CI: 1.72, 4.31). Individuals with plaque generally had more unfavourable cardiovascular risk factor levels, regardless of educational level. However, after risk factor adjustment those with both low education and carotid plaque still had a two-fold increased risk of CE. The results imply that differences in the prevalence of preclinical atherosclerosis seem important in explaining education differences in future coronary morbidity.

Introduction

The existence of graded associations between educational level and cardiovascular health is well documented and relatively undisputed. In addition, it has been shown that people with low educational level are more likely to have more extensive preclinical carotid artery disease [1], [2], [3], which in turn is known to be associated with future cardiovascular morbidity and mortality [4], [5], [6], [7]. Thus, a prominent hypothesis is that the elevated morbidity and mortality risk associated with low levels of education is primarily due to the higher prevalence of preclinical atherosclerotic lesions.

The purpose of the present study was to bring clarity to this issue by addressing the following questions: (1) does a potential association between education and incidence of coronary events persist after stratification for the presence of preclinical atherosclerosis in the carotid arteries and (2) is there an increased susceptibilty to presence of preclinical atherosclerosis in groups with low educational achievement.