Unravelling behavioural contributions to IBS risk: evidence from univariate and multivariate Mendelian randomisation.

Background: While numerous studies have investigated the link between behavioural factors and irritable bowel syndrome (IBS), the causal relationships remain unresolved. This study applied Mendelian randomisation (MR) analysis to assess the causal impact of specific behavioural factors on IBS risk.

Methods: Bidirectional Mendelian randomisation analysis was employed to evaluate the causal relationships between behavioural factors and IBS risk. A genome-wide significance threshold (P < 5e^-6) was applied to identify associations between genetic variants and behaviour-related traits, ensuring robust selection of instrumental variables for evaluating potential causal effects. Genetic correlations with IBS were sourced from extensive genome-wide association studies (GWASs). Various statistical methods were applied to estimate the causal effects.

Results: This study employed both univariate and multivariate Mendelian randomisation analyses to investigate the causal relationships between specific behavioural factors and the risk of irritable bowel syndrome (IBS). The results indicated that body mass index (BMI) (odds ratio (OR) = 1.074; 95% confidence interval (CI) = 1.025-1.125, P = 0.031), insomnia (OR = 1.986; 95% CI = 1.652-2.389, P < 0.001), duration of mobile phone use (OR = 1.120; 95% CI = 1.018-1.232, P = 0.021), and weekly mobile phone usage time in the past three months (OR = 1.148; 95% CI = 1.016-1.298, P = 0.021,) were associated with an increased risk of IBS. In contrast, usual walking speed (OR = 0.756; 95% CI = 0.621-0.920, P < 0.001), non-smoking status (OR = 0.779; 95% CI = 0.645-0.941, P < 0.001), and weekly alcohol consumption (OR = 0.862; 95% CI = 0.743-0.999, P = 0.015) were associated with a reduced risk of IBS. Furthermore, in the multivariate Mendelian randomisation analysis, no statistically significant causal associations were found for BMI, usual walking pace, length of mobile phone use, and smoking status. Weekly mobile phone usage time in the past three months (OR = 1.439; 95% CI = 1.126-1.840, P = 0.0037,) and insomnia (OR = 1.468; 95% CI = 1.076-2.003, P = 0.0156) were identified as risk factors, while weekly alcohol intake (OR = 0.813; 95% CI = 0.677-0.975, P = 0.0257) acted as a protective factor.

Conclusions: This study identified BMI, insomnia, duration of mobile phone use, and weekly mobile phone usage time in the past three months as risk factors for IBS. In contrast, weekly alcohol consumption, usual walking pace, and non-smoking status were observed as protective factors. Additionally, in multivariable analysis, weekly mobile phone use, insomnia, and weekly alcohol consumption showed a direct influence on IBS risk when considered simultaneously.