Chromium Exposure and Risk of Cardiovascular Disease in High Cardiovascular Risk Subjects　- Nested Case-Control Study in the Prevention With Mediterranean Diet (PREDIMED) Study.

BACKGROUND Epidemiological data on chromium (Cr) exposure and the risk of cardiovascular disease (CVD) are still limited. Toenail Cr level (TCL) provides a time-integrated measure reflecting long-term Cr exposure. We measured TCL to assess the hypothesis that long-term Cr exposure was inversely associated with incident CVD in a population at high risk for CVD.Methods and Results:The associations between TCL and CVD were evaluated in a case-control study nested within the "PREvención con DIeta MEDiterránea" (PREDIMED) trial. We randomly selected 147 of the 288 patients diagnosed with CVD during follow-up and matched them on age and sex to 271 controls. Instrumental neutron activation analysis was used to assess TCL. In-person interviews, medical record reviews, and validated questionnaires were used to assess covariates. The fully adjusted OR for the highest vs. lowest quartile of toenail Cr was 0.54 (95% CI: 0.26-1.14; Ptrend=0.189) for the nested case-control study. On stratification for diabetes mellitus (DM), OR was 1.37 (95% CI: 0.54-3.46; Ptrend=0.364) for the DM group, and 0.25 (95% CI: 0.08-0.80; Ptrend=0.030) for the non-DM group (P for interaction=0.078). CONCLUSIONS The present findings, although not statistically significant, are consistent with previously reported inverse associations between TCL and CVD. These results, especially for non-DM patients, increase the limited epidemiological knowledge about the possible protective role of Cr against CVD. (Trial registration: www.controlled-trials.com; ISRCTN35739639.).