Comparative analysis of the variability of carotid intima-media thickness in primary prevention populations of Moscow and Paris.

It is well-known that the distribution of traditional cardiovascular risk factors (CVRFs) of atherosclerosis, including hypertension, dyslipidemia, smoking, obesity, and diabetes is considerably variable between different countries, however, with some important geographical trends. Thus, CVRFs contribute differently to atherosclerosis development in different countries. Common carotid artery intima-media thickness (CCA IMT) is a validated biomarker of subclinical atherosclerosis that is used in clinical and epidemiological studies to evaluate the impact of CVRFs on atherosclerosis development. This comparative cohort study included a random sample of 1200 participants (n = 600 men and n = 600 women) from Moscow, Russia and Paris, France, aged between 55 and 79 years, and free of clinical symptoms of atherosclerosis. The study was conducted to determine the interpopulation variability of CCA IMT. CCA IMT was measured by ultrasonic scanning at the high-resolution regimen. Statistical analysis was performed using Stata 9.1. For comparison of mean values of continuous variables, Mann-Whitney U-test was used; Chi-square, Pearson's test was used for comparison of categorical variables. To determine to what extent presented differences can be explained by differences in traditional CVRFs, the regression model was applied. Path analysis (plug Passport Litigation Decision Analysis & Optimization Module, Datacert, USA) was used to assess the impact of traditional CVRFs on the CCA IMT in both Moscow and Paris study populations. There was a significant difference in the distribution of most of the traditional CVRFs between the study populations, including blood pressure, lipid profile, statin treatment, hormone replacement therapy in women, and CVD history. The remarkably high level of difference in the mean values of the CCA IMT was found between Moscow and Paris study populations. In women of both Moscow and Paris study populations, the mean value of CCA IMT was 0.78 and 0.63, respectively. In men of both Moscow and Paris study populations, the mean CCA IMT value was 0.84 and 0.67, respectively. In the Moscow study population, the effects (direct and indirect) of traditional CVRs can explain 42% of the CCA IMT variance in women and 30% - in men. In the Paris study population, direct and indirect effects of traditional CVRFs can explain 27% of the CCA IMT variance in men and 14% - in women. The Paris study population significantly differed from the Moscow study population in the distribution and impact of traditional CVRFs. Traditional CVRFs can explain only a small proportion of the interpopulation differences in CCA IMT suggesting the presence of other factors, such as longitude, which can possibly influence these differences. Therefore, this study provided an additional piece of evidence towards the existence of a geographic gradient of carotid IMT.