Association between hypertension and frozen shoulder: A bidirectional two-sample mendelian randomization study

Observational studies have suggested a potential association between hypertension and frozen shoulder. This study aims to elucidate the causal dynamics of this relationship using a bidirectional 2-sample Mendelian randomization approach. We analyzed data on hypertension (N = 484,598) and frozen shoulder (N = 627,998) from the IEU Open genome-wide association study database. Instrumental variables were carefully selected to ensure robust correlation and minimize linkage disequilibrium. The primary analysis was conducted using the inverse variance-weighted (IVW) method. Additional analyses, including the Weighted Median, MR-Egger, Simple Model, and Weighted Model, were performed to further assess causal effects. We conducted heterogeneity and pleiotropy tests, along with a leave-one-out analysis, to evaluate the stability of our findings. Our analysis revealed that individuals with hypertension have a significantly increased risk of developing frozen shoulder (IVW: odds ratio = 1.749, 95% CI: 1.275-2.399, P = 5.239*10-4). Conversely, reverse Mendelian randomization analysis showed no significant association between frozen shoulder and the risk of hypertension (IVW: odds ratio = 1.006, 95% CI: 0.991-1.021, P = .426). Our findings confirm that hypertension is associated with an increased risk of frozen shoulder, while the reverse does not hold. Patients with hypertension should be informed of this potential risk and consider preventive strategies against the development of frozen shoulder.