Association between genetically determined telomere length and health‐related outcomes: A systematic review and meta‐analysis of Mendelian randomization studies

Emerging evidence has shown that leukocyte telomere length (LTL) is associated with various health‐related outcomes, while the causality of these associations remains unclear. We performed a systematic review and meta‐analysis of current evidence from Mendelian randomization (MR) studies on the association between LTL and health‐related outcomes. We searched PubMed, Embase, and Web of Science up to April 2022 to identify eligible MR studies. We graded the evidence level of each MR association based on the results of the main analysis and four sensitive MR methods, MR‐Egger, weighted median, MR‐PRESSO, and multivariate MR. Meta‐analyses of published MR studies were also performed. A total of 62 studies with 310 outcomes and 396 MR associations were included. Robust evidence level was observed for the association between longer LTL and increased risk of 24 neoplasms (the strongest magnitude for osteosarcoma, GBM, glioma, thyroid cancer, and non‐GBM glioma), six genitourinary and digestive system outcomes of excessive or abnormal growth, hypertension, metabolic syndrome, multiple sclerosis, and clonal hematopoiesis of indeterminate potential. Robust inverse association was observed for coronary heart disease, chronic kidney disease, rheumatoid arthritis, juvenile idiopathic arthritis, idiopathic pulmonary fibrosis, and facial aging. Meta‐analyses of MR studies suggested that genetically determined LTL was associated with 12 neoplasms and 9 nonneoplasm outcomes. Evidence from published MR studies supports that LTL plays a causal role in various neoplastic and nonneoplastic diseases. Further research is required to elucidate the underlying mechanisms and to bring insight into the potential prediction, prevention, and therapeutic applications of telomere length.