Global incidence of chronic lymphocytic leukemia: A systematic review and meta-analysis

Background Chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) is a slow-growing cancer, which requires substantial resources for monitoring and management. CLL is most common among older people; however, there is a lack of understanding of its incidence in some regions of the world, such as Asia and Africa. This study aimed to examine the global incidence rates of CLL and assess variations across regions and countries.Method This systematic review and meta-analysis followed the Joanna Briggs Institute manual for Evidence Synthesis and the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) statement. Databases including EBSCOHost platform, Embase, Medline via Ovid, and Google Scholar were searched up to 31 May 2026 (PROSPERO ID: CRD42023463669). Two groups of reviewers independently performed title, abstract, full-text screening and quality assessment. Meta-analysis was conducted using a random-effects model to estimate the pooled incidence rate. Bias assessment and multilevel meta-analysis for exploring sources of heterogeneity and time trends were also performed.Results A total of 44 articles met inclusion criteria out of 8752 identified records. The pooled age-standardised incidence rate was 1.37 per 100,000 person-years, 95% CI (1.19; 1.57), 90% PI (0.57; 3.30), I2= 99.94%. Significant variations were observed in both crude incidence and age-standardised incidence across countries (τ2=0.34 and τ2=0.17, respectively) and regions (τ2=2.44 and τ2=0.97, respectively). North America had higher incidence rate, while lower incidence rates observed in Asia and Africa. Multilevel meta-analysis showed that heterogeneity was largely attributable to the geographical aggregation, with higher heterogeneity at region level (ie, 84.7%) and lower heterogeneity at the country level (ie, 15.2%). Standardised incidence rates were increasing but have stabilised since the 2000s" CONCLUSION: Substantial variations in CLL incidence exists across countries and regions. Further research examining epidemiological factors related to disease progression, genetic profiles and improved in diagnostic reporting is recommended.