Lower urinary tract symptoms (LUTS) including overactive bladder (OAB) largely affect the patient’s quality of life. Recent reports suggest LUTS as an independent risk factor for falls and bone fractures. In elderly patients with LUTS, falls or bone fractures result in a significant decline in the activities of daily living. In addition, they have also been found to closely related to the prognosis of LUTS patients. However, no clinical studies are available for predicting bone fracture occurrence in LUTS patients. The fracture risk assessment tool (FRAX) was developed to calculate the 10-year probability of bone fracture. It is based on 12 clinical risk factors which can be used for screening of primary and hip bone fracture risk in both osteoarthritis patients and healthy individuals. Herein, the study aimed to examine bone fracture risk in OAB patients using FRAX and evaluate the correlation between OAB symptom severity and bone fracture risk.

We enrolled subjects (age, >40 years) with de novo OAB and age-matched controls and analyzed between-group differences in bone fracture risk using FRAX. Severity assessment was performed using OAB symptom score (OABSS) with OAB patients (OABSS: urgency ≥2, total score ≥3). In addition, bone fracture risk was analyzed among the groups based on OAB severity (non-OAB, mild-OAB (OABSS≤5), and moderate/severe-OAB (OABSS≥6)). We excluded patients currently undergoing osteoarthritis treatment and those with medical comorbidities (e.g., acute urinary tract infection, neurogenic bladder, etc.) and a prostate volume >30 g. A p-value <0.05 was considered statistically significant. 
All participants provided written informed consent.

Of the 244 individuals, 97 and 147 were in the OAB group and non-OAB groups, respectively. There was no statistical difference between the two groups in age (OAB group: 70.9±10.3; non-OAB group: 68.9±10.7; p=0.130). In the OAB group, statistically significantly higher proportion of women (OAB group: n=63, 65.0%; non-OAB group: n=74, 54.1%; p=0.026), and increased 10-year primary bone (OAB group: 19.7±13.3%, non-OAB group: 11.8±10.3%; p<0.001) and hip bone fracture risks (OAB group: 8.9±9.1%; non-OAB group: 4.7±7.9%; p<0.001) were observed than in the non-OAB group. Positive correlations were shown between individual 4 OABSS items and total OABSS, with primary bone fracture risk, where Q3 (urgency) showed strongest correlation (total OABSS: r=0.408, Q1, daytime frequency: r=0.217; Q2, nighttime frequency: r=0.358; Q3: r=0.368; Q4, urgency incontinence: r=0.225; p<0.001). In addition, evaluation of bone fracture risk and OAB severity showed that the moderate/severe-OAB group had the highest primary bone fracture risk (non-OAB group: 11.8±10.3%, mild-OAB: 15.6±11.4%, moderate/high-OAB: 21.8±13.8; p<0.001) and hip bone fracture risk (non-OAB group: 4.8±7.5%, mild-OAB: 6.6±7.8%, moderate/high-OAB: 10.0±9.5%; p<0.001).

OAB patients show a high risk for bone fracture, with a significant association with OAB symptom severity. The findings have therapeutic implications where active cooperation between orthopedics and urologists and designing exercise-based programs may prevent bone fracture risk in patients with severe OAB symptoms.

This study suggested that OAB patients had a higher risk of bone fracture, and the severity of OAB was associated with fracture risk.