Association between circulating leptin levels and systemic lupus erythematosus: an updated meta-analysis

Objective: We aimed to evaluate the relationship between circulating leptin levels and systemic lupus erythematosus (SLE). Methods: MEDLINE, EMBASE, and Cochrane library databases were searched. Meta-analyses were performed comparing serum/plasma leptin levels in patients with SLE and healthy controls, and on patients with SLE in subgroups based on ethnicity, sample size, data type, and matched variables (age, sex, and/or body mass index (BMI)). Results: Eighteen studies including 1333 patients with SLE and 1048 controls were ultimately selected, which showed that leptin levels were significantly higher in the SLE group than in the control group (SMD = 0.611, 95% CI = 0.275–0.947, p < 0.001). When we excluded two outlier studies because of high heterogeneity, leptin levels were also significantly higher in the SLE group than in the control group (SMD = 0.619, 95% CI = 0.431–0.807, p < 0.001). Stratification by ethnicity showed significantly elevated leptin levels in the SLE group in European, Asian, Arab, Latin American, and mixed populations. Subgroup analysis by sample size showed significantly higher leptin levels in the SLE group by small (n ≤ 100) and large sample numbers (n > 100) (SMD = 0.780, 95% CI = 0.445–1.115, p < 0.001; SMD = 0.495, 95% CI = 0.275–0.715, p < 0.001). Stratification by data type revealed significantly higher leptin levels in the original data and imputed data groups. Subgroup analysis adjustment revealed significantly higher leptin levels in the SLE group, regardless of adjustment for variables. Conclusions: Our meta-analysis demonstrated that leptin levels were significantly higher in patients with SLE, regardless of ethnicity, sample size, data type, and matched variables.