Researchers Report a High Rate of Concurrent Irritable Bowel Syndrome in Patients with Overactive Bladder

To investigate whether irritable bowel syndrome (IBS) and overactive bladder (OAB) share common pathological characteristics, the authors of “Relationship between Overactive Bladder and Irritable Bowel Syndrome: A Large-Scale Internet Survey in Japan Using the Overactive Bladder Symptom Score and Rome III Criteria,” published in BJU International, used an Internet survey to document co-occurrence of IBS and OAB in a cohort of Japanese adults.

Previous studies have shown that both IBS and OAB are prevalent in the general population and frequently occur concurrently. Other studies have suggested an association between the two conditions, including reports that the bladder and large intestine may share “common afferent nerve projections, suggesting the presence of neural cross-talk between these two organs.”

For the current study, the authors assembled a cohort of 10,000 adults age 20 years or older (5,000 men and 5,000 women), organized into five age groups: age 20—29, 30–39, 40–49, 50–59, and age 60+. Each age group contained 1,000 people. Participants were first given the Rome III IBS criteria questionnaire, followed by the OAB symptom score (OABSS) questionnaire.

The authors reported the following results based on participants’ survey scores:

• Overall OAB prevalence was 9.3% (9.7% in men, 8.9% in women)
• OAB was mild in 59% of subjects, moderate in 40%, and severe in 1%
• Overall IBS prevalence was 21.2% (18.6% in men, 23.9% in women)

Of patients who met Rome III criteria for IBS, 28% had IBS-diarrhea (IBS-D), 48% had IBS-mixed (IBS-M), and 17% had IBS-constipation (IBS-C).

Among male participants, IBS-M was the most common subtype (45%), followed by IBS-D (28%) and IBS-C (10%). In women, the most common IBS subtype was IBS-M (49%), followed by IBS-C (23%) and IBS-D (22%).

The survey data showed some overlap between the two conditions in this cohort. One-third (33.3%) of participants with OAB also had IBS (32% of men with OAB and 34.8% of women). OAB prevalence increased with age, while IBS prevalence decreased with age, especially in men. The authors reported that “the prevalence of association of OAB and IBS was stable at around 3% of all five age groups.”

One-third (33.3%) of patients with mild OAB had IBS, as did 32.8% of patients with moderate OAB and 38.5% of patients with severe OAB.

Based on these results, the authors concluded that although the prevalence rates of OAB and IBS “differ depending on age and gender, the present survey showed that these diseases occurred concurrently in some cases and that OAB was complicated by IBS, particularly in about one-third of OAB patients.” Because of this, it is “important to assess the defecation habits of patients when diagnosing and treating OAB, especially younger patients with OAB.” They recommend that further studies be conducted to examine the relationship between IBS and lower urinary tract symptoms and to “elucidate what impact IBS has on treatment outcome of patients with OAB.”