Results of MR analysis
We analyzed the causal relationship between telomere length and the percentage of immune cells using the inverse variance weighted method, and the results are shown in Figure 2. The results revealed a significant correlation between telomere length and the percentage of T lymphocytes (OR: 1.222, 95% CI: 1.014-1.472, P = 0.035), indicating a causal relationship between shorter telomere length and lower T cell percentage. However, no significant association was observed between telomere length and the percentage of B cells and NK cells.
Further analysis of T cell subsets indicated that shorter telomere length may lead to a lower proportion of Natural Killer T cells (OR: 1.574, 95% CI: 1.281-1.935, P < 0.001), particularly CD8+ Natural Killer T cells (OR: 1.534, 95% CI: 1.268-1.856, P< 0.001). Additionally, shorter telomere length was associated with a higher percentage of CD4 regulatory T cells (OR: 0.761, 95% CI: 0.624-0.929, P = 0.007), especially Activated CD4 regulatory T cells (OR: 0.787, 95% CI: 0.649-0.955, P = 0.015), as well as a higher percentage of Effector Memory CD8+ T cells (OR: 0.818, 95% CI: 0.693-0.966, P = 0.018). Analysis of B cell subsets revealed that shorter telomere length may be associated with a higher proportion of Transitional B cells (OR: 0.735, 95% CI: 0.602-0.897, P = 0.003), Naive-mature B cells (OR: 0.789, 95% CI: 0.650-0.958, P= 0.017), and a lower proportion of Memory B cells (OR: 1.305, 95% CI: 1.075-1.584, P = 0.007).
Scatter plots also clearly illustrate this relationship (Figure 3). The results of the four additional supplementary analyses, including weighted mode, weighted median, simple mode, and MR-Egger regression, also support the same conclusion. And the detailed results can be found in Table S3.