HDL-C, triglycerides and carotid IMT: a meta-analysis of 21,000 patients with automated edge detection IMT measurement

Objective: Common carotid artery (CCA) intima-media thickness (IMT), low-density lipoprotein cholesterol (LDL-C), and high-density lipoprotein cholesterol (HDL-C), but not triglyceride levels, are markers of future cardiovascular events. The relationship between these three factors is, however, unclear. Methods: We included six large observational studies that used the same harmonized, B-mode ultrasound protocol,thesamesoftwareforIMTmeasurementbyautomaticedgedetectiononCCAinaplaque-freeregion, followingthe Mannheim consensus,andcertificationofallsonographers. Using the best viewof the CCA, the sonographerhadto confirmthat thequalityindex was � 0.5 on ameasurement performedon10-mmlength. We used individual data meta-analysis to estimate the cross-sectional associations of lipids with CCA-IMT. Results: Overall,21,587patients withcompleteinformation onlipids andCCA-IMTwere available. Age-and sex-adjusted CCA-IMT differed by � 7.8 mm (95% CI � 9.1 to � 6.5 mm, P < 0.001) per 1 SD higher HDL-C level. Afterfurtheradjustmentforotheratherosclerosisriskfactors,therelationshipwasattenuated,butremained significant (regression coefficient, � 3.7 mm; P < 0.001). This was found regardless of LDL-C levels (P for heterogeneity ¼ 0.70). After adjustment for age and sex, triglycerides were positively associated with CCAIMT, overall and in each LDL-C subgroup, but not after further adjustments for other risk factors. Conclusions: Relationships between HDL-C and triglyceride levels and CCA-IMT were consistent with that previously observed with clinical events by the Emergency Risk Collaboration group, including at low LDL-C levels. This reinforces the need to verify whether raising HDL-C levels decreases both CCA-IMT and future clinical events.