JMIR Publications

ABSTRACT

Background:

Emerging evidence suggests that irritable bowel syndrome (IBS) extends beyond a localized gastrointestinal disorder and may involve systemic dysregulation, including alterations in autonomic function. Vasovagal syncope (VVS), the most common form of reflex syncope, is also closely linked to autonomic imbalance. Despite shared pathophysiological features, the longitudinal association between IBS and VVS has not been well characterized in large population-based studies.

Objective:

To evaluate the risk of vasovagal syncope among individuals with irritable bowel syndrome.

Methods:

We conducted a nationwide, population-based cohort study using a large health insurance database to evaluate the risk of VVS among individuals with IBS. Patients with IBS were identified using standardized diagnostic criteria and matched to non-IBS controls using propensity score matching based on demographic and clinical variables. To enhance diagnostic specificity, VVS was defined using a composite algorithm incorporating ICD-10 code R55, a confirmatory diagnostic procedure, and recurrent diagnosis within 3 months. Participants were followed longitudinally to identify incident VVS cases. Incidence rates were calculated per 1,000 person-years, and incidence rate ratios (IRRs) were estimated. Cox proportional hazards models were used to calculate adjusted hazard ratios (aHRs) with 95% confidence intervals (CIs), controlling for age, sex, lifestyle factors, metabolic parameters, and socioeconomic status. Kaplan–Meier analyses were performed to assess cumulative incidence, and subgroup analyses were conducted by age, sex, and IBS subtype (with and without diarrhea).

Results:

During follow-up, individuals with IBS had a higher incidence of VVS compared to matched controls. The crude incidence rates were 3.11 and 2.37 per 1,000 person-years in the IBS and control groups, respectively (IRR 1.31, 95% CI: 1.23–1.39). In multivariable analyses, IBS was associated with an increased risk of VVS (aHR 1.30, 95% CI: 1.21–1.39). This association was consistent across IBS subtypes, including IBS with diarrhea (aHR 1.27, 95% CI: 1.15–1.41) and IBS without diarrhea (aHR 1.35, 95% CI: 1.24–1.46). The elevated risk persisted across age and sex groups, with slightly stronger relative effects among individuals younger than 60 years. Kaplan–Meier curves demonstrated a sustained separation in cumulative incidence between groups over time.

Conclusions:

IBS is associated with a modest but consistent increase in the risk of VVS, independent of major confounders. Given the high prevalence of IBS, this association may have meaningful population-level implications. The findings support a potential link mediated by autonomic dysfunction and gut–brain axis dysregulation and highlight the need for further mechanistic studies and integrated clinical approaches to address extraintestinal manifestations of IBS.