Exploring the Causality of Type 1 Diabetes and Stroke Risk: A Mendelian Randomization Study and Meta-analysis

Type II diabetes was causally related to stroke, which is a risk factor for stroke. However, the causal relationship between type I diabetes(T1D) and stroke, especially its subtypes, remains unclear. To determine whether T1D has a genetic causal link to stroke and its subtypes, we undertook this mendelian randomization (MR) study. The genome-wide association studies (GWAS) of T1D was the source of exposure. The outcomes were strokes and their subtypes, including ischemic stroke (IS), small vessel stroke (SVS), cardioembolic stroke (CES), large artery atherosclerosis stroke (LAS), intracerebral hemorrhage (ICH), lobar intracerebral hemorrhage (LICH), and non-lobar intracerebral hemorrhage (NLICH). We used outcome GWAS conducted by ISGC consortium for the initial phase and GWAS from MEGASTROKE consortium as the data for the replication phase to confirm the causal association. Besides, we conducted a meta-analysis of the causal association from ISGC and MEGASTROKE databases to confirm robust causality. Inverse-variance weighting (IVW) was utilized as the primary method to estimate the causality between T1D and stroke. The Cochran's Q test and the MR-PRESSO global test were used to examine the sensitivity. We discovered the causal relationship between T1D and SVS (OR = 1.17, 95% CI: 1.07-1.28, p = 6.0 × 10^- 4), CES (OR = 1.11, 95%CI: 1.03-1.21, p = 0.0080) in initial stage. The replication phase validated T1D has a causal relationship with SVS (OR = 1.12, 95% CI: 1.06-1.18, p = 4.0 × 10^- 5), but not with stroke and other subtypes. The meta-analysis of initial and replication stage again supported the causal link between T1D and SVS (OR = 1.13, 95% CI: 1.08-1.18, p < 0.05). However, no causal relationship was found between T1D and other stroke subtypes. The sensitivity analysis also supported the robust of these results. In conclusion, T1D was causally associated with SVS, but not with other subtypes of stroke. More investigation is needed to understand the underlying biology mechanism.