Relation of Coronary Artery Calcium and Extra-Coronary Aortic Calcium to Incident Hypertension (from the Multi-Ethnic Study of Atherosclerosis)

Abstract

Arterial calcification reflects an atherosclerotic process associated with vascular stiffness. Whether baseline coronary artery calcium (CAC) and extra-coronary calcium (ECC), measured using noncontrast computed tomography imaging, are associated with incident hypertension is poorly understood. We studied participants from the Multi-Ethnic Study of Atherosclerosis without measured or self-reported hypertension at baseline. Incident hypertension was defined by blood pressure criteria (BP, ≥140/90 mmHg), BP medication use, or both, and was assessed at in-person visits. We analyzed incident hypertension using multivariable-adjusted discrete-time proportional hazards models. Net reclassification improvement (NRI) assessed whether CAC reclassified hypertension risk when added to the Framingham hypertension risk score. Among 3,304 subjects analyzed, mean age was 59 ± 10 years; 48% were male and 42% were white. There were 1,283 incident hypertension cases over a median (interquartile range) follow-up time of 10.6 (4.5, 11.5) years. Each 1-unit increase in ln(CAC+1) was independently associated with a 12% higher risk of hypertension (95% confidence interval [CI] 9% to 16%). Relative to CAC = 0, patients with CAC >400 had a hazard ratio for incident hypertension of 2.2 (95% CI 1.8 to 2.9). There was no interaction by age, gender, or baseline BP (p = 0.43, 0.19, 0.09, respectively). Continuous NRI analyses demonstrated that CAC can reclassify risk of incident hypertension; NRI = 0.19 (95% CI 0.10 to 0.26). Furthermore, all measurements of ECC were significantly associated with incident hypertension, even after adjustment for CAC (hazard ratios ranging from 1.36 to 1.38). In conclusion, patients with CAC and ECC are at markedly higher risk of incident hypertension and may benefit from more intensified prevention efforts.