Systematic Review and Meta-Analysis of the Association Between ABO Blood Groups and Anaemia Prevalence Among Young Adults Aged 18-25 Years

Background: Anaemia is a common societal problem affecting young adults, especially in low- and middle-income nations, and there is currently a body of evidence indicating that it has a genetic component through the ABO blood groups, affecting iron metabolism and erythrocyte stability. This is a systematic review of evidence on the association between ABO blood groups and anaemia in young adults aged 18-22 years. Material and Methods: According to the PRISMA principles, we used the following keywords: ABO blood group anaemia, young adults, and blood group anaemia in medical students in PubMed, Google Scholar, and ResearchGate (until December 2025). Inclusion criteria: The cross-sectional studies in healthy young adults (18-22 years) with reports on ABO distribution and anaemia prevalence (WHO criteria: Hb <12 g/dL and Hb <13 g/dL, respectively). The extracted data included sample size, methods, prevalence by ABO group, and odds ratios (ORs). Synthesis of the narrative and qualitative evaluation was conducted (Newcastle-Ottawa Scale); a meta-analysis was not possible because of the heterogeneity. Results: Eight studies (1,418 participants; most of them medical/dental students in India) were included based on the criteria. The general anaemia level was 26-45. Three studies have found significant associations, with blood group A showing an increased risk (crude OR=2.8-3.2 vs. O; p<0.05). Four Indian studies found no significant trends supporting B or O being more risky. In a Ghanaian study on malaria, the A was 16-17.8-fold risk. Heterogeneity existed in methodological differences (e.g., Hb cutoffs less than 10 vs. less than 12 g/dL; Sahli's vs. automated). Conclusion: Blood group A is associated with increased susceptibility to anaemia in young adults, which aligns with malaria-carrying patterns in a global malaria-endemic area but conflicts with Indian data. High-risk groups are recommended to be ABO-stratified and screened. To establish causality and mechanisms, larger, standardised prospective studies are required.

Keywords: Anemia, ABO blood groups, Young adults, Systematic review, Iron metabolism, Public Health.