**1. Introduction**

Overactive bladder (OAB) and diabetes mellitus (DM) are common health threats and both increase in incidence and prevalence with advancing age. Several epidemiological studies have shown that OAB is more common in patients with type 2 DM than in the general population, and women with DM treated with insulin have higher odds (OR 3.5, 95% CI 1.6–7.9) of urge incontinence than those treated with non-insulin medication [1,2]. A study investigating the prevalence and correlation of urinary incontinence and OAB conducted in Taiwan showed that women who were elderly and menopausal and had a history of DM or hypertension and higher body mass index were significantly predisposed to an OAB [3]. Higher glycosylated hemoglobin levels represented an independent predictor of OAB symptoms among DM patients [4]. Even in early-stage DM, type 2 DM in male patients age <45 years

had more OAB symptoms and erectile dysfunction than the controls [5]. Regarding OAB management, a study of 36,560 OAB patients in the US found that patients with DM are more persistent and adherent to OAB medications and have higher odds of filling a second medication prescription than patients without DM [6]. These factors may imply that DM is an important risk factor of OAB, but conventional oral medication is usually not as effective for OAB patients with DM.

We conducted a review of the published literature in Pubmed, using a combination of two keywords, namely "botulinum toxin A" (BoNT-A) and "overactive bladder" with or without the additional keywords "detrusor overactivity", "diabetes mellitus", "inflammation", and "urodynamic study". We reviewed the pathophysiology of DM-associated OAB, the anti-inflammatory effects of BoNT-A, and the clinical evidence for intravesical BoNT-A injection in patients with DM-associated OAB. We aimed to clarify the role of BoNT-A treatment in these patients.
