Association Between Heavy Metals Exposure and Elevated High-Sensitivity C-Reactive Protein: Mediating Role of Body Mass Index

Heavy metal exposure is linked to obesity and systemic inflammation. This study explored the mediating role of body mass index (BMI) in the association of heavy metal exposure with high-sensitivity C-reactive protein (hs-CRP). Blood levels of mercury (Hg), cadmium (Cd), and lead (Pb) were assessed in a nationwide sample of 4521 adults. Linear regressions were employed to examine associations among blood heavy metal levels, BMI, and hs-CRP levels. Mediation analyses were conducted to estimate the indirect effect of exposure to each heavy metal on the elevation of hs-CRP through an increase in BMI. The median (Q1; Q3) values for blood levels of heavy metals were 3.15 (2.10; 4.84) for Hg (μg/L), 0.95 (0.63; 1.38) for Cd (μg/L), and 1.67 (1.28; 2.21) for Pb (μg/dL). Blood Hg level was associated with both BMI (adjusted <i>β</i>: 0.73; 95% CI [confidence interval]: 0.51; 0.96) and a log-transformed hs-CRP level (adjusted <i>β</i>: 0.07; 95% CI: 0.02; 0.13). Blood Cd and Pb levels showed no clear associations with BMI and hs-CRP. The indirect effect of Hg exposure on hs-CRP via BMI was 0.069 (95% CI: 0.037; 0.102), and that of the direct effect was 0.003 (95% CI: -0.001; 0.007), with BMI accounting for 95.7% (95% CI: 88.6%, 102.0%) of the total association between Hg levels and hs-CRP levels. Hg exposure was linked to increased hs-CRP levels, with elevated BMI explaining most of this association. This research offers insights into the mechanisms through which Hg contributes to systemic inflammation, underscoring the potential role of BMI as a key mediator.