The Relationship between Telomere Length and Epigenetic Aging with Hematologic Diseases Risk: A Multivariable Mendelian Randomisation Study
Authors: Li Yang , Jia Chen , Sun Ting , Yang Renchi , Zhang Lei 
Published: December 2023

Introduction: Aging is a complex phenomenon that involves multifaceted changes, including significant alterations in telomere length and epigenetic aging. When aging affects the hematopoietic system, it leads to a gradual increase in mutations in hematopoietic stem cells, making individuals more susceptible to the development of hematologic diseases. However, due to the limitations of observational studies, such as potential confounding factors and reverse causality, the precise causal direction and magnitude of the relationship between telomere length, epigenetic aging, and the incidence of hematologic diseases remain uncertain. Therefore, we conducted an investigation to determine the causal relevance of telomere length and epigenetic aging in relation to hematologic diseases using Mendelian randomization (MR).

Methods: Firstly, we conducted a 2-sample single-variable Mendelian randomization (SVMR) study to examine the genetically predicted effects of telomere length and epigenetic age acceleration, as measured by HannumAge, Horvath Intrinsic Age, PhenoAge, GrimAge, and DNAm PAI-1 (DNA methylation-estimated plasminogen activator inhibitor-1) levels, on multiple hematologic diseases, including anemia, lymphoma, leukemia, myeloproliferative diseases, and hemostasis and coagulation diseases. Additionally, we used lasso regression to exclude multicollinearity in SNPs and subsequently performed multivariable MR using the screened SNPs to adjust for statistically significant risk factors, and MR Bayesian model averaging was performed to rank the significant risk factors based on their genetic evidence (Figure A).

Results: Summary data were available for 19 malignant hematological neoplasms and 35 non-malignant hematological disorders, corresponding to 70,813 cases and 12,253,012 controls. Increased telomere length due to germline genetic variation was generally associated with increased risk for hematologic diseases. The strongest associations were observed for lymphoma, lymphoid leukaemia, Hodgkin lymphoma, chronic lymphocytic leukaemia, essential thrombocythaemia, unspecified types of non-Hodgkin lymphoma, multiple myeloma, Non-follicular lymphoma, unspecified iron deficiency, leukaemia, while higher levels of telomere length was associated with a reduced risk of pernicious anaemia (Figure B). Meta-analyzed IVW MR findings suggested that higher PhenoAge acceleration was associated with increased risks of myeloid leukemia, chronic lymphocytic leukemia, and lymphoid leukemia. Conversely, higher PhenoAge acceleration was linked to reduced risks of unspecified disorders of white blood cells and unspecified coagulation defects. Similarly, SVMR showed genetic predisposition for GrimAge acceleration to be associated with increased risks of amyloidosis, unspecified anemias, and myeloid leukemia. Conversely, genetically predicted GrimAge acceleration was associated with reduced risks of hemorrhagic anemia, hemolytic anemias, and idiopathic thrombocytopenic purpura. Furthermore, our findings suggested that elevated HannumAge acceleration increased the risks of lymphoma, leukemia, and lymphoid leukemia.Conversely, higher HannumAge acceleration was associated with a reduced risk of chronic myeloid leukemia. Additionally, higher levels of DNAm PAI-1 were found to be associated with an increased risk of chronic myeloid leukemia. However, there was no evidence of causality between genetically predicted Intrinsic epigenetic age acceleration and the 19 malignant hematological neoplasms and 35 non-malignant hematological disorders mentioned (Figure C). We utilized MVMR-LASSO to estimate the combined effects of telomere length and five epigenetic clocks on hematologic diseases. After adjusting for epigenetic aging, we observed a significant positive association between telomere length and various hematologic diseases, including leukemia, lymphoid leukemia, chronic lymphocytic leukemia, lymphomas, Hodgkin lymphoma, non-follicular lymphoma, unspecified types of non-Hodgkin lymphoma, essential thrombocythemia, and multiple myeloma (Figure D&E).

Conclusion: Longer telomeres and epigenetic aging may increase the risk of developing most hematologic malignancies, while simultaneously raising or decreasing the risk of certain non-malignant hematologic diseases.