Association of Intima‐Media Thickness Measured at the Common Carotid Artery With Incident Carotid Plaque: Individual Participant Data Meta‐Analysis of 20 Prospective Studies

BACKGROUND: The association between common carotid artery intima‐media thickness (CCA‐IMT) and incident carotid plaque has not been characterized fully. We therefore aimed to precisely quantify the relationship between CCA‐IMT and carotid plaque development. METHODS AND RESULTS: We undertook an individual participant data meta‐analysis of 20 prospective studies from the Proof‐ATHERO (Prospective Studies of Atherosclerosis) consortium that recorded baseline CCA‐IMT and incident carotid plaque involving 21 494 individuals without a history of cardiovascular disease and without preexisting carotid plaque at baseline. Mean baseline age was 56 years (SD, 9 years), 55% were women, and mean baseline CCA‐IMT was 0.71 mm (SD, 0.17 mm). Over a median follow‐up of 5.9 years (5th–95th percentile, 1.9–19.0 years), 8278 individuals developed first‐ever carotid plaque. We combined study‐specific odds ratios (ORs) for incident carotid plaque using random‐effects meta‐analysis. Baseline CCA‐IMT was approximately log‐linearly associated with the odds of developing carotid plaque. The age‐, sex‐, and trial arm–adjusted OR for carotid plaque per SD higher baseline CCA‐IMT was 1.40 (95% CI, 1.31–1.50; I (2)=63.9%). The corresponding OR that was further adjusted for ethnicity, smoking, diabetes, body mass index, systolic blood pressure, low‐ and high‐density lipoprotein cholesterol, and lipid‐lowering and antihypertensive medication was 1.34 (95% CI, 1.24–1.45; I (2)=59.4%; 14 studies; 16 297 participants; 6381 incident plaques). We observed no significant effect modification across clinically relevant subgroups. Sensitivity analysis restricted to studies defining plaque as focal thickening yielded a comparable OR (1.38 [95% CI, 1.29–1.47]; I (2)=57.1%; 14 studies; 17 352 participants; 6991 incident plaques). CONCLUSIONS: Our large‐scale individual participant data meta‐analysis demonstrated that CCA‐IMT is associated with the long‐term risk of developing first‐ever carotid plaque, independent of traditional cardiovascular risk factors.