Association between lymphatic filariasis and diabetes mellitus: A systematic review and narrative synthesis

Abstract Background: Lymphatic filariasis (LF) and diabetes mellitus (DM) increasingly coexist as important health challenges in low- and middle-income countries. Chronic filarial infection induces marked immunoregulation that may influence inflammatory pathways implicated in insulin resistance, providing biological plausibility for an interaction between the two conditions. We synthesised epidemiological, immunological, endocrine, and clinical evidence on the LF–DM relationship. Methodology/Principal Findings: The review followed PRISMA 2020 guidance, and its protocol was prospectively registered in PROSPERO (CRD420261331823). MEDLINE and Scopus were searched for records available from database inception through 2 May 2026. Additional eligible literature was identified through Google Scholar and citation-based searching. We considered studies involving human participants in whom LF had been established using recognized diagnostic, clinical, or programme-based criteria. Studies reporting diabetes or other relevant metabolic, immunological, or clinical outcomes were eligible for inclusion. Study quality was assessed using the Newcastle-Ottawa Scale, and the certainty of the available evidence was evaluated using the GRADE approach. Variation across the included studies precluded quantitative pooling; therefore, findings were synthesized narratively. Seven studies fulfilled the eligibility criteria. All were conducted in India, with most originating from a single research network. Overall, the epidemiological evidence indicated an association between LF and lower diabetes prevalence. The largest study additionally reported lower circulating concentrations of selected pro-inflammatory cytokines among participants with LF. Conclusions/Significance: Evidence suggests a biologically plausible interaction between LF and DM but remains too limited and geographically concentrated for firm conclusions. The absence of studies from sub-Saharan Africa is a critical gap. Longitudinal, mechanism-focused studies across diverse LF-endemic settings are needed to clarify this relationship and inform integrated care for populations bearing dual neglected tropical disease and non-communicable disease burdens.