Multilevel Models to Estimate Carotid Intima-Media Thickness Curves for Individual Cardiovascular Risk Evaluation

Abstract

Background and Purpose— The value of carotid intima-media thickness (cIMT)—a marker of subclinical atherosclerosis—in defining the cardiovascular risk is still debated. The aim of this study was to estimate standard cIMT progression, adjusting values over time for the main cardiovascular risk factors, in a sample of low-to-moderate cardiovascular risk subjects, to identify normative cIMT progression values. Methods— From the progression of lesions in the intima of the carotid cohort, we selected subjects who underwent 4 planned serial clinical evaluations and ultrasound cIMT determinations, on average every 4 years. Subject taking glucose-lowering therapies in secondary cardiovascular prevention or with cardiovascular risk score >5 were excluded from the analysis. The growth of cIMT across the study period (12 years) was assessed by use of individual growth curve modeling within multilevel models. Results— A total of 1175 (36% men; mean age, 53±11 years at baseline) participants at low/intermediate cardiovascular risk have been included in this analysis. A significant and marked slope of the mean and maximum cIMT growth curves (β=0.009 and β=0.012, respectively) was observed, confirming that it is a function of age. A stratified analysis by decades of age highlighted a nonlinear cIMT progression over time. In addition, different patterns of cIMT development between sex were observed. Finally, different slopes in mean and maximum cIMT curves, with a significant spread since the fifth decade, were observed in the cIMT growth curve models of subjects developing multifocal carotid atherosclerosis compared with the rest of the population. Conclusions— These findings proved that the rate of change in cIMT over time is a sign of the development of atherosclerosis, which cannot be a priori assumed linear. These data, therefore, support the clinical relevance of these growth curve models for cIMT progression to be considered as useful tool to identify subjects with faster atherosclerosis progression and thus at increased cardiovascular risk.