Fig. 2. Mediation effect model of uric acid on the BMI-SBP association in children (upper) and adults (lower).

BMI = body mass index; SBP = systolic blood pressure. β, c and c′ are standardized regression coefficients; c = total effect; c′ = direct effect; β₁ = indirect effect 1; β₂ = indirect effect 2; β_Ind = total indirect effect (β₁ × β₂). Coefficients different from 0: **P < 0.01. $\begin{array}{c}\mathrm{Indirect}\mathrm{effect}\left({\mathrm{\beta }}_{\mathrm{Ind}}\right)={\mathrm{\beta }}_1\times {\mathrm{\beta }}_2=0.365\times 0.076=0.028\hfill \\ 0.322\times 0.105=0.033\hfill \end{array}$ $\begin{array}{c}\mathrm{Total}\mathrm{effect}\left(\mathrm{c}\right)=\mathrm{Direct}\mathrm{effect}\left(c\prime \right)+\mathrm{Indirect}\mathrm{effect}\left({\mathrm{\beta }}_{\mathrm{Ind}}\right)=0.289+0.028=0.317\hfill \\ 0.212+0.033=0.245\hfill \end{array}$ $\begin{array}{c}\mathrm{Mediation}\mathrm{effect}=\left({\mathrm{\beta }}_1\times {\mathrm{\beta }}_2\right)/\mathrm{c}\times 100=0.028/0.317\times 100=8.8\%\hfill \\ 0.033/0.245\times 100=13.5\%\hfill \end{array}$.