Baseline determinants of carotid intima media thickness (IMT) in a high risk European population: the baseline results of the IMPROVE study

Aim: The “IMPROVE study” is a prospective, multicenter, longitudinal, observational study designed to investigate whether cross-sectional carotid artery intima media thickness (IMT) and overall IMT-progression are predictors of future vascular events in European individuals at high risk of cardiovascular diseases. The present report describes the results of the baseline analyses aimed to identify the major determinants of increased carotid IMT. Methods:. A total of 3711 subjects (age range 54-79 years) with at least 3 vascular risk factors (VRFs) were recruited in 7 centers of 5 European countries (Finland, France, Italy, the Netherlands and Sweden). Collected variables included clinical, biochemical, genetic, socio-economic, psychological, nutritional, and educational data, personal and family history of diseases, drug intake and physical activity. Results: By multiple linear regression analyses, carotid IMT was strongly and positively associated with centre-latitude, age, gender, pulse pressure, pack-years and hypertension, and inversely with educational level. Latitude was the strongest independent determinant of carotid IMT and alone accounted for nearly half of the variation explained by the regression model. The geographical gradient for carotid IMT paralleled the North to South cardiovascular mortality gradient. Conclusions: Latitude is a major determinant of carotid IMT which is not explained by between-country differences in established VRFs. Other unknown contributory mechanisms such as heritable, nutritional or environmental factors may be important in the genesis of this geographical gradient. Funding: European Project, IMPROVE QLG1-CT-2002-00896