Karl Andersen^1,2,3

Thor Aspelund^1,3

Elías Freyr Guðmundsson³

Gunnar Sigurðsson⁴

Sigurður Sigurðsson³

Guðlaug Björnsdóttir¹

Bolli Þórsson³

Gunnar Sigurðsson^1,3

Þórður Harðarson^1,3

Vilmundur Guðnason^1,3

¹Faculty of Medicine, School of Health Sciences, University of Iceland, ²Division of Cardiovascular Services, Landspitali University Hospital, Iceland, ³The Icelandic Heart Association, ⁴Skåne University Hospital, Sweden.

Correspondence: Karl Andersen, andersen@landspitali.is

Key words: socioeconomic status, education, risk factors, cardiovascular disease.

INTRODUCTION: Educational attainment is related to improved health and longevity. We investigated the relationship between educational attainment and cardiovascular risk factors, subclinical atherosclerosis, and incidence of coronary artery disease.

MATERIAL AND METHODS: The Reykjavik REFINE study is a population-based study recruiting 6616 subjects, 25-69 years of age from the greater Reykjavik area in 2005-2011. Baseline measurements of cardiovascular risk factors were performed, and all participants had a carotid ultrasound examination to detect subclinical atherosclerotic lesions. Clinical follow-up of cardiovascular disease during a ten-year period was performed. Educational attainment was related to clinical outcome measures.

RESULTS: The study population comprised of 3251 men and 3365 women. The proportion of the study population with primary school education only was 20.1%, 31.2% had vocational training, 12.3% had high school education and 36.4% were university graduates. Traditional cardiovascular risk factors were generally higher among subjects with primary school education only. Compared to subjects with university education, the odds ratio of having severe atherosclerotic plaque was 1.84 (95% CI 1.40-2.43) among those with primary school education only and 1.49 (95% CI 1.16-1.91) among subjects with vocational training. The subjects with high school or university education were less likely to develop significant cardiovascular disease during the 10-year follow-up period.

CONCLUSION: Primary school and vocational training compared to university education are associated with risk factors of atherosclerotic disease, subclinical carotid plaque, and incidence of cardiovascular disease. The reason for this disparity remains to be clarified but socioeconomic inequality related to less educational attainment might be involved.

Table I. Baseline characteristics according to educational attainment.

Table II. Odds Ratio for severe atherosclerotic plaque according to cardiovascular risk factors and educational attainment. Logistic regression.

Table III. Hazard ratio for cardiovascular disease incidence according to risk factors and educational attainment. Cox regression.

Figure 1. Main cardiovascular risk factors according to educational attainment. Metabolic syndrome is defined according to the American Heart Association (AHA). At least three of the following criteria are required for the diagnosis of metabolic syndrome:

-waist circumference of at least 40 inches (102 cm) in men or 35 inches (89 cm) in women

-Triglyceride level of at least 150 mg per dL (1.70 mmol per L), or receiving pharmacologic therapy for elevated triglyceride levels

-HDL cholesterol level of less than 40 mg per dL (1.05 mmol per L) in men or less than 50 mg per dL (1.30 mmol per L) in women, or receiving pharmacologic therapy for reduced HDL cholesterol levels

-Systolic blood pressure of at least 130 mm Hg or diastolic blood pressure of at least 85 mm Hg, or receiving pharmacologic therapy for hypertension

-Fasting glucose level of at least 100 mg per dL (5.6 per L), or receiving pharmacologic therapy for elevated fasting glucose levels.

Figure 2. Prevalence of severe atherosclerotic plaque according to educational attainment, age and sex.

Figure 3. Odds Ratios and and 95% Confidence Intervals of severe atherosclerotic plaque by educational attainment. Adjustments made for age and sex (black), and age, sex, of risk factors and risk factors (green).

Figure 4. Hazard Ratios and and 95% Confidence Intervals of cardiovascular disease by educational attainment. Adjustments made for age and sex (black), and age, sex, risk factors and risk factors (yellow).

Figure 5. Kaplan-Meier survival plot of the incidence of cardiovascular disease by educational attainment and sex.