This study aimed to ascertain whether there is an independent association between serum magnesium
(Mg) and the Carotid Intima-Media Thickness (IMT-CC), a well-accepted atherosclerotic-biomarker
surrogate of cardiovascular disease (CVD), in a population with high cardiovascular risk. Serum Mg
and traditional atherosclerotic risk factors were recorded in 939 patients (mean age, 59.6 ± 0.3 years,
83.2% men) with coronary heart disease (CHD) enrolled in the CORDIOPREV trial. Serum Mg strongly
associated with IMT-CC. Before adjusting for potential confounding factors, IMT-CC decreased by
0.111 ± 0.011 mm per mg/dl increase in serum Mg (p < 0.001). After adjustment, the effect of Mg did
not appear mediated through factors related to glucose metabolism, the lipid profile or the mineral
metabolism and renal function. Multivariate models showed the lower Mg levels (quartile 1) as a strong
independent factor contributing to IMT-CC along with age, sex, SBP, HDL-C, and diuretic use. Logistic
regression analysis confirmed the predictive ability of serum Mg to differentiate patients at higher
atherosclerotic risk as defined by an IMT-CC ≥ 1.0 mm, yielding a OR for the lower quartile of 10.623
(95%CI 2.311–48.845; P = 0.002) and a ROC-derived cutoff of 1.61 mg/dl. Therefore, our findings outline
low serum magnesium as a possible independent risk factor for carotid atherosclerosis.