# Mendelian randomization analysis reveals causal relationship between tonsillectomy and irritable bowel syndrome

## TL;DR

This study finds a genetic link suggesting that tonsillectomy may increase the risk of developing irritable bowel syndrome.

## Contribution

The study provides new evidence of a causal relationship between tonsillectomy and IBS using Mendelian randomization.

## Key findings

- Genetically predicted tonsillectomy is positively associated with IBS (OR = 1.682).
- Results show heterogeneity among SNPs but no evidence of horizontal pleiotropy.
- Sensitivity analysis confirms the stability of the findings.

## Abstract

This study used two sample Mendelian randomization (MR) method to evaluate the causal relationship between tonsillectomy and irritable bowel syndrome (IBS).

We selected tonsillectomy as the exposure factor and IBS as the outcome variable, using GWAS data from the IEU Open GWAS project. Instrumental variables (IVs) were SNPs strongly correlated and independent of tonsillectomy. MR-PRESSO was used for outlier removal. IVW was the primary MR analysis method, supplemented by MR-Egger regression, WM, WME, and simple mode. Cochran's Q tests assessed heterogeneity. MR-Egger intercept tested horizontal pleiotropy. Sensitivity analysis used a leave-one-out method.

The IVW analysis indicated a positive association between genetically predicted tonsillectomy and IBS (OR = 1.682, 95% CI: 1.157–2.446, P = 0.006). Heterogeneity tests revealed the presence of heterogeneity at the SNPs (Cochran Q test, P = 3.13 × 10−5. The MR-Egger intercept test did not detect horizontal pleiotropy (egger_intercept = 0.000914, P = 0.789). Sensitivity analysis demonstrated the stability of the results. All F-statistics were greater than 10, indicating the absence of weak instrument bias.

Genetics predicts a positive causal relationship between tonsillectomy and IBS, suggesting that prevention of IBS in tonsillectomy patients should be enhanced.