Figure 8. Subgroup analysis of LPO levels stratified according to sex. The test for subgroup differences showed no statistically significant subgroup effect (p = 0.62), indicating that sex did not modify the effect of MT intervention, compared with vehicle-treated groups. However, considerable heterogeneity was observed in the male (I2 = 89%) and female (I2 = 56%) subgroups. The unit for LPO almost in all studies is nmol/mg, except Nogues MR et al. (nmol/mL). The prism represents the overall statistical results of the experimental data, squares represent the weight of each study, and horizontal lines represent the 95% CIs for each study. LPO, lipid peroxidation; MT, melatonin; I, heterogeneity; CI, confidence interval; SD, standard deviation; IV, independent variable.