Irritable bowel syndrome not a risk factor for Parkinson’s disease

Individuals with irritable bowel syndrome (IBS) do not appear to be at increased risk of developing Parkinson’s disease compared with those who do not have IBS, according to the results of a Mendelian randomization analysis.

Researchers used a dataset involving 426,911 participants from the UK Biobank. Cox proportional hazards models and case-control analysis were used to explore the association between IBS and Parkinson’s disease, with factors such as age, gender, ethnicity, and education level included as covariates.

The analysis included 419,685 participants, of which 4.71 percent had IBS and the 95.29 percent without IBS comprising the control group. Participants in the IBS group were more likely to be women, have a slightly lower frequency of alcohol intake and educational level, have a higher proportion of nonsmokers, have poorer overall health, and have a higher prevalence of long-term illness, disability, or frailty.

The mean follow-up time was 13.93 years for the IBS group and 14.08 years in the control group. Univariate Cox regression model showed that the risk of Parkinson’s disease was reduced in the IBS group (hazard ratio [HR], 0.774; 95 percent confidence interval [CI], 0.625–0.956; p=0.017), although the statistical significance decreased following adjustments for other variables.

Additional analysis wherein five healthy control participants were matched to each IBS patient based on gender and age confirmed the lack of association between IBS and the risk of Parkinson’s disease (odds ratio [OR], 1.239; 95 percent CI, 0.896–1.680; p=0.181).

Mendelian randomization showed no significant evidence of a causal relationship between IBS and Parkinson’s disease (OR, 0.801; 95 percent CI, 0.570–1.278; p=0.204).