Inflammation Tied to Overactive Bladder Odds, Partly via Adiposity

Higher levels of systemic inflammation were associated with greater odds of overactive bladder (OAB) among US adults, with measures of adiposity contributing to up to 37% of the association, according to a cross-sectional analysis recently published in Medicine.¹

Blood Cell Index May Capture Inflammatory Burden in OAB

OAB, characterized by sudden, hard-to-defer urges to urinate, erodes quality of life and carries a substantial economic burden.² Chronic inflammation, abnormal fat metabolism, and neuromodulatory changes have all been implicated in OAB, but its primary drivers remain unclear.¹ Investigators noted that identifying modifiable risk factors could help inform targeted prevention and management strategies.

To explore the role of inflammation, they examined the association between OAB and the aggregate index of systemic inflammation (AISI), which incorporates neutrophil, monocyte, lymphocyte, and platelet counts. Because obesity is closely linked to both chronic inflammation and OAB, they also assessed whether measures including body mass index (BMI), relative fat mass (RFM), weight-adjusted waist index (WWI), and body roundness index (BRI) could mediate the association between AISI and OAB.

The researchers used data from 5 cycles of the National Health and Nutrition Examination Survey (NHANES), spanning 2009-2018, to clarify the epidemiologic links among inflammation, obesity, and OAB.

Adiposity Indices Mediate Inflammation-OAB Association

The investigators analyzed 18,601 adults 20 years and older. OAB was identified using questionnaire items on urge incontinence and nocturia, scored with the Overactive Bladder Symptom Score; a total of 3719 participants met the criteria.

Compared with participants without OAB, those with OAB were older (57.5 vs 45.8 years) and more often women (64.6% vs 49.2%). Participants with OAB also had a lower income-to-poverty ratio (2.61 vs 3.16) alongside higher rates of diabetes (26.0% vs 10.9%) and hypertension (59.4% vs 34.1%). Disparities emerged: non-Hispanic Black adults made up 16.9% of the OAB group vs 8.9% of the non-OAB group, and 21.1% of patients with OAB had less than a high school education vs 11.4% of the non-OAB group.

After adjusting for demographic and clinical covariates, each 1-unit increase in log-transformed AISI was associated with 17% higher odds of OAB (OR, 1.17; 95% CI, 1.07-1.29). Participants in the highest AISI quartile had 21% higher odds than those in the lowest (OR, 1.21; 95% CI, 1.02-1.44).

However, the relationship was not linear. Below a log-transformed AISI of 5.71, inflammation levels showed no association with OAB (OR, 1.00; 95% CI, 0.91-1.10). Above it, each unit increase corresponded to 50% higher odds (OR, 1.50; 95% CI, 1.32-1.70). The authors noted that the clinical meaning of this data-driven cut point requires further investigation.

In addition, age significantly modified the association (P for interaction = .038). The link was strongest among adults aged 20 to 45 years (OR, 1.31) and remained significant in those older than 65 years (OR, 1.13). By contrast, the relationship was not statistically significant in those aged 46 to 65 years (OR, 1.08).

Mediation analysis estimated that BRI accounted for the largest share of the AISI-OAB association (37.1%), followed by RFM (36.2%), BMI (31.3%), and WWI (26.4%); a significant direct association remained in every model. Plausible pathways include sustained intra-abdominal pressure on the bladder from central obesity and obesity-related insulin resistance, the authors noted.

They added that a whole blood count profile could eventually serve as an adjunctive biomarker to identify patients with elevated inflammatory burden, pending longitudinal validation.

Where the Results Fit in OAB Research

The study joins several recent NHANES analyses tying OAB to cardiometabolic factors rather than bladder function alone. One found that BMI was the largest driver of the association between cardiovascular health scores and OAB, while a systemic inflammation index accounted for 4.8% of that relationship.³

In a separate machine learning model built on data from US women, BMI ranked among the strongest contributors to OAB risk, which climbed steeply above approximately 33.7 kg/m².⁴ Specialty guidance has moved in the same direction: the 2024 guideline update from the American Urological Association and the Society of Urodynamics, Female Pelvic Medicine & Urogenital Reconstruction addresses obesity among the nonurological factors relevant to OAB care.⁵

At the same time, the authors acknowledged several limitations to their study.¹ The cross-sectional design prevents it from establishing causality, and the mediation findings reflect statistical associations rather than confirmed biological pathways. In addition, the findings may not generalize beyond the US, and excluding participants with missing data may have introduced selection bias. Still, the authors framed their findings as a jumping-off point for further research.

"This provides novel epidemiological evidence for understanding the complex interplay among inflammation, obesity, and OAB and may inform future longitudinal investigations into its prevention and management," they concluded.

References

1. Du H, Wang L, Zhou H. Association between systemic inflammation and overactive bladder: the potential mediating role of obesity-related anthropometric indices. Medicine (Baltimore). 2026;105(37):e50574. doi:10.1097/MD.0000000000050574
2. Onukwugha E, Zuckerman IH, McNally D, Coyne KS, Vats V, Mullins CD. The total economic burden of overactive bladder in the United States: a disease-specific approach. Am J Manag Care. 2009;15(suppl 4):S90-S97.
3. Joszt L. Better cardiovascular health tied to lower overactive bladder risk. AJMC^®. September 1, 2026. Accessed September 25, 2026. https://www.ajmc.com/view/better-cardiovascular-health-tied-to-lower-overactive-bladder-risk
4. McCormick B. Overactive bladder predictors in women extend beyond age, BMI. AJMC. September 25, 2026. Accessed September 25, 2026. https://www.ajmc.com/view/overactive-bladder-predictors-in-women-extend-beyond-age-bmi
5. Cameron AP, Chung DE, Dielubanza EJ, et al. The AUA/SUFU guideline on the diagnosis and treatment of idiopathic overactive bladder. J Urol. 2024;212(1):11-20. doi:10.1097/JU.0000000000003985