PD Influence on Irritable Bowel Syndrome: Study Discoveries

Researchers investigate the connection between irritable bowel syndrome (IBS) and Parkinson’s disease (PD) in a new study that was published in npj Parkinson’s Disease.

What leads to Parkinson’s disease?

Bradykinesia, stiffness, and resting tremors are frequent symptoms of Parkinson’s disease (PD), a neurological illness. These symptoms usually appear years before Parkinson’s disease (PD) is officially diagnosed; cognitive decline and gastrointestinal issues typically occur before motor symptoms.

Although the precise causation of Parkinson’s disease (PD) is unknown, genetic and environmental factors may play a role. Evidence has been shown to associate Parkinson’s disease (PD) with gastrointestinal symptoms, which may be associated with altered gut microbiota, increased intestinal permeability, or altered gut-brain communication.

The symptoms of IBS, a functional gastrointestinal disorder, include persistent or recurrent abdominal pain and changes in bowel habits. There may be a connection between PD and IBS, according to current research, although the findings of these investigations have been contradictory.

Concerning the study

For the current investigation, data from 426,911 people aged 40 to 69 who were enrolled in 22 centers between 2006 and 2010 were taken from the United Kingdom Biobank (UKBB). For every follow-up, IBS patient, five age- and sex-matched healthy controls were also included. Up to the time of PD diagnosis, research termination in June 2023, or death, whichever came first, all trial participants were followed up on.

The study didn’t include those participants with missing data and those with additional neurological and gastrointestinal conditions. Similarly, participants with pre-study PD diagnoses as well as those whose IBS diagnosis date was uncertain were not included in the analysis. Together, 26,944 people received a PD diagnosis and 2,460 an IBS diagnosis based on International Classification of Disease-10 (ICD-10) codes.

The odds ratios (ORs) for the correlation between PD and IBS were computed using logistic regression analysis, while the hazard ratios (HRs) were determined using Cox proportional hazard models. Age, sex, body mass index (BMI), Townsend deprivation index, educational attainment, ethnicity, alcohol use, smoking status, general health, and chronic medical issues were among the study’s confounders.

Additionally, sensitivity analyses were carried out by grouping participants based on whether they were diagnosed with IBS before or after 2000 and eliminating those who self-reported having the disorder. Mendelian randomization (MR) analyses, which included the simple mode, weighted mode, weighted median, MR Egger, and inverse variance weighting (IVW) methods, were also used to examine the relationship between PD and IBS utilizing genotype data as instrumental factors.

Study results

Of the 419,685 participants in the Cox modeling, 95% made up the control study group, and 4.7% had an IBS diagnosis before the start of the trial. For a mean of 14 years, both groups were under observation.

IBS patients had higher odds of being female, having less education, not smoking, drinking less alcohol, being in worse health, and having more comorbidities than controls. 90 IBS patients and 2,321 controls were diagnosed with Parkinson’s disease during follow-up; the case and control groups’ respective incidence rates were 3.2 and 4.2 in 10,000 individual years.

With an HR of 0.8, univariate Cox regression analysis showed that PD risk was lower in IBS patients. In some subgroup analyses, people with IBS and those diagnosed with IBS after 2000 (HR = 0.6) were linked to a lower risk of Parkinson’s disease.

Subgroup analysis showed that, with HRs of 0.8, 0.6, 0.6, and 0.8, respectively, IBS was linked to a lower incidence of Parkinson’s disease (PD) in white people, people with a history of smoking, people with a BMI between 25 and 29.90, and those with less education than a college degree.

Univariate Cox regression study revealed a decreased risk of Parkinson’s disease (PD) among IBS patients, with an HR of 0.8. IBS sufferers and those diagnosed with the disorder after 2000 (HR = 0.6) were associated in some subgroup analyses with a decreased risk of Parkinson’s disease (PD).

Subgroup analysis revealed that IBS was associated with a lower incidence of Parkinson’s disease (PD) in white individuals, those with a history of smoking, those with a BMI between 25 and 29.90, and those with less education than a college degree, with HRs of 0.8, 0.6, 0.6, and 0.8, accordingly.

Among non-IBS patients with a polygenic risk score of PD with an HR of 2.2, there was a statistically significant increase in the risk of PD. Similar results were obtained in the sensitivity analysis when self-reported IBS patients were excluded.

IBS was associated with a lower incidence of Parkinson’s disease (PD) with an HR of 0.6 in those with IBS diagnoses made after 2000. IBS did not lower the incidence of Parkinson’s disease (PD), according to a case-control study, and the results of MR analysis corroborated these findings.

In conclusion

Although certain patient subgroups may have a lower chance of receiving a PD diagnosis, IBS patients do not seem to be more prone to acquiring PD. However, more research is required to clarify underlying mechanisms and gain a deeper understanding of the possible association between PD and IBS.

For more information: Association between irritable bowel syndrome and Parkinson’s disease by Cohort study and Mendelian randomization analysis, npj Parkinson’s Disease, doi:10.1038/s41531-024-00691-5