Comparative Morphometry of Carotid Arteries Across Ethnic Groups

Thesis Abstract

This study addresses the clinical and anatomical question of whether carotid artery morphometry varies across ethnic groups, with implications for stroke risk assessment, vascular intervention planning, and population-specific reference values. Recognizing limited cross-ethnic morphometric data, the research posits that measurable arterial parameters such as lumen diameter, intima-media thickness, wall thickness, and cross-sectional area exhibit statistically and clinically meaningful differences that may influence hemodynamics and atherosclerotic progression. The aim is to quantify inter-ethnic differences in carotid morphometry and identify independent predictors among demographic, anthropometric, and vascular risk factors. Specific objectives are (i) to estimate mean differences in common carotid and internal carotid artery diameters, intima-media thickness, and cross-sectional area across major ethnic groups; (ii) to assess the association between morphometric variables and age, sex, body mass index, blood pressure, lipid profile, and glucose tolerance within each group; (iii) to evaluate whether ethnicity modifies the relationship between conventional cardiovascular risk factors and carotid morphometry using interaction terms; and (iv) to develop ethnicity-adjusted reference ranges for carotid morphometric parameters. The methodology adopts a cross-sectional, multi-center design. The population comprises adults aged 35–75 years from four distinct ethnic groups within an urban-metropolitan setting. A stratified random sampling strategy yields a total sample size of 1,000 participants (250 per group), calculated to achieve 80% power to detect small-to-moderate effect sizes (Cohen's d = 0.30) in lumen diameter differences at a 5% significance level, accounting for potential 10% non-response. Data collection employs high-resolution duplex ultrasonography to measure common carotid artery diameter, intima-media thickness, and bulb characteristics bilaterally, with standardized protocols and blinded image analysis. Additional instruments include a structured demographic and risk-factor questionnaire, calibrated blood pressure measurements, complete lipid panels, fasting glucose, and HbA1c. Inter-rater and intra-rater reliability for morphometric metrics are assessed via intraclass correlation coefficients on a random subset (n=100) of scans. Analytical approaches comprise descriptive statistics to summarize morphometric parameters by ethnicity, followed by multivariate analysis. Analysis of covariance (ANCOVA) assesses adjusted mean differences across groups, with age, sex, BMI, systolic blood pressure, LDL-C, HDL-C, triglycerides, fasting glucose, and smoking status as covariates. Multiple linear regression models identify independent predictors of carotid morphometry within each ethnicity, and interaction terms explore whether ethnicity modifies risk-factor associations. Where nonlinear patterns emerge, generalized additive models (GAM) are employed. To address multiple comparisons, the false discovery rate is controlled using the Benjamini-Hochberg procedure. A conceptual framework integrating the metabolic syndrome theory and the hemodynamic stress model guides interpretation, with the possibility of incorporating the race-based susceptibility framework to contextualize findings within broader cardiovascular health disparities. Expected findings include statistically significant inter-ethnic variations in mean common carotid and internal carotid artery diameters, intima-media thickness, and cross-sectional areas, after adjusting for confounders. It is anticipated that ethnic groups with higher prevalence of hypertension and insulin resistance will exhibit thicker intima-media and altered wall shear stress proxies, contributing to differential stroke risk profiles. The study is expected to reveal that ethnicity moderates the impact of traditional risk factors on morphometric parameters, with stronger associations between systolic pressure and carotid thickness in certain groups. The research will contribute to knowledge by providing robust, population-specific carotid morphometry reference ranges, improving risk stratification and informing culturally sensitive vascular screening guidelines. The study's contributions to knowledge include empirical evidence on cross-ethnic carotid morphometry, methodological advancement through standardized imaging protocols in a multi-ethnic cohort, and the potential to refine ethnicity-adjusted diagnostic thresholds for carotid pathology. Practical implications extend to tailoring preventive strategies and surveillance intervals in diverse populations, enhancing precision medicine in vascular health. Limitations include cross-sectional design precluding causal inferences and potential residual confounding from unmeasured lifestyle factors. Conclusions anticipate that ethnicity-related variations in carotid morphometry exist beyond conventional risk factors and should be integrated into clinical assessment and normative data. Recommendations emphasize the development of ethnicity-specific reference values in radiology reporting, longitudinal studies to elucidate causal pathways, and exploration of genetic and environmental contributors to morphometric diversity.