Common carotid intima-media thickness in cardiovascular risk stratification of older people: the Rotterdam Study

Aim: Non-invasive measures of atherosclerosis, such as carotid intima-media thickness (cIMT), may improve global cardiovascular risk prediction. The aim of this study was to determine whether common carotid IMT in addition to traditional risk factors improves risk classification in a general population of older people. Methods and results: A group of 3580 non-diabetic people aged 55-75 years and free of cardiovascular disease at baseline were followed for a median time of 12.2 years. Compared to models based on Framingham risk factors, we studied the ability of common cIMT measurement to better classify people into categories of low (<10%), intermediate (10-20%) and high (>20%) 10-year risk of hard coronary heart disease (CHD) and stroke. In older men, addition of cIMT to Framingham risk factors did not improve prediction of hard CHD or stroke. In older women, addition of cIMT to Framingham risk factors significantly improved risk classification. cIMT improved the C-statistic of the model for hard CHD from 0.711 to 0.719 and for stroke from 0.712 to 0.721, at good calibration. Reclassification was least in the majority of women classified as low risk (4% (n=76) for hard CHD and 3% (n=62) for stroke) and most substantial in women at intermediate risk (43% (n=70) for hard CHD and 28% (n=76) for stroke). The net reclassification improvement in women was 8.2% (p=0.03) for hard CHD and 8.0% (p=0.06) for stroke. Conclusion: cIMT had some additional value beyond traditional risk factors in the cardiovascular risk stratification of older women, but not of older men.