We aimed to systematically review the incidence of diabetes mellitus (DM) in patients with preexisting hematological malignancy (HM) and investigate the risk factors contributing to DM incidence.

A systematic search was performed in PubMed, Scopus, Web of Science, and Google Scholar according to PRISMA guidelines. Pooled estimates were calculated using a random-effects model with restricted maximum likelihood (REML) estimation of between-study variance and the Hartung–Knapp adjustment for confidence intervals (CIs). Heterogeneity was assessed using the Q test, τ², I², and 95% prediction intervals, with I² values above 50% indicating substantial variability. Additionally, we performed subgroup analyses based on relevant risk factors. Publication bias and small-study effects were evaluated using funnel plots and Egger’s test, and influence diagnostics were performed through leave-one-out analyses.

A total of 37 studies were included in this study. An increased pooled risk measure of 2.83 (95% CI: 2.12–3.77) for DM incidence was reported in the HM group compared to the control group. Among reported risk factors, obesity (2.10, 95% CI: 1.10–3.99), receiving total body irradiation (TBI) (2.08, 95% CI: 1.58–6.02), dyslipidemia (2.60, 95% CI: 1.09–6.20), and HLA mismatch (1.56, 95% CI: 1.13–2.15) demonstrated significant association with a higher incidence of DM among HM patients. However, no significant association was observed between DM incidence and risk factors including sex, hypertension (HTN), type of donor in bone marrow transplant, graft-versus-host disease (GvHD), positive DM family history, and anthracycline usage.

The meta-analysis supports the hypothesis that DM incidence is significantly higher in HM patients, which requires early prevention and effective intervention for this population. Yet, more prospective studies with high sample sizes and follow-up duration are recommended.