Methods and results:
The measured CAC in 2220 MESA participants were compared with those in 3126 HNR participants with the inclusion criteria such as age 45–75 years, Caucasian race, and free of baseline cardiovascular disease. Despite similar mean levels of CAC of 244.6 among participants in MESA and of 240.3 in HNR (P ¼ 0.91), the prevalence of CAC . 0 was lower in MESA (52.6%) compared with HNR (67.0%) with a prevalence rate ratio of CAC . 0 of 0.78 [95% confidence interval (CI): 0.72–0.85] after adjustment for known risk factors. Consequently, among participants with CAC . 0, the participants in MESA tended to have higher levels of CAC than those in HNR (ratio of CAC levels: 1.39; 95% CI: 1.19–1.63), since many HNR participants have small (near zero) CAC values.
The CAC prevalence was lower in the United States (MESA) cohort than in the German (HNR) cohort, which may be explained by more favourable risk factor levels among the MESA participants. The predictors for increased levels of CAC were, however, similar in both cohorts with the exception that male gender, blood pressure, and body mass index were more strongly associated in the HNR cohort.
Two prospective studies have simultaneously been initiated, the American MESA (Multi-Ethnic Study of Atherosclerosis) and the German Heinz Nixdorf Recall Study (HNR) to evaluate the value of coronary artery calcium (CAC) levels for risk prediction using cardiac CT.
The aim of Erbel et al in the presented study was to compare the prevalence of cardiovascular risk factors and their association with CAC between the United States and Germany.
After all exclusion criteria were applied, the final study population consisted of 2220 subjects from MESA and 3126 from HNR.
The main conclusions of Erbel et al are:
- Coronary artery calcification prevalence was lower in the United States (MESA) cohort than the German (HNR) cohort. This was partially explained by generally more favourable risk factor levels among the MESA participants, which could be shown for men and women.
- CAC was significantly associated with age, gender, current smoking, treated diabetes, hypertension, and hypercholesterolaemia.
- Risk factor associations were comparable across the two studies, with the exception that male gender, blood pressure, and BMI were more strongly associated with CAC in the German cohort. Germany showed higher rates of hypercholesterolaemia and smoking, but less obesity and use of lipid-lowering medication.
- This study reveals local differences in distribution of cardiovascular risk factors and coronary artery calcium scores. Whether this will also translate into differences of “hard end points” remains open to speculation and will be answered in the next years.