Hypothesis / aims of study
Nocturia is defined by the International Continence Society (ICS) as waking at night to void. It is a common and bothersome lower urinary tract symptom that negatively impacts quality of life (1,2).
Nocturia is a complex issue with many contributing factors, and it's possible that it's related to underlying bladder dysfunction (3). The aim was to determine whether people who experience nocturia show different urodynamic test results.
Study design, materials and methods
A retrospective analysis was performed on 3427 patients undergoing urodynamic testing at a tertiary referral centre. Patients were stratified according to nocturia symptoms. Independent-samples Mann–Whitney U tests were used to compare variables between groups.
Chi-square analysis was performed to explore associations between nocturia and urodynamic diagnoses, including urodynamic stress incontinence (USI), detrusor instability, neurogenic detrusor overactivity, low compliance, urgency, voiding difficulty, prolapse and normal bladder function.
Results
Differences in urodynamic parameters were observed between the two patient groups (Table 1). The first sensation to void was similar, with a median of 200 mL (IQR 120–300 mL in those with nocturia vs 110–300 mL in patients without nocturia; p < 0.001). Maximum cystometric capacity was also similar, with a median of 500 mL (IQR 400–546 mL without nocturia; 400–540 mL with nocturia; p < 0.001).
Those with nocturia had a significantly higher voided volumes (490 mL, IQR 400–540 mL) compared to those who didn't have nocturia (450 mL, IQR 330–529 mL; p < 0.001). Additionally, the peak flow rate was higher in patients with nocturia (17 mL/s, IQR 10–25); those without nocturia had a lower rate (14 mL/s, IQR 0–25; p < 0.001). The maximum detrusor pressure was higher in patients without nocturia (22 cmH₂O, IQR 12.5–30 vs 20 cmH₂O, IQR 15–30; p < 0.001).
There were differences in urodynamic diagnoses in patients with and without nocturia (Table 2). Mild USI was found in 7.8% of patients with nocturia (113/1452), which is similar to 7.6% of patients without nocturia (150/1975). With moderate USI, 16.1% of patients with nocturia had it (234/1452), compared to 13.3% of those without nocturia (262/1975). Similarly, severe USI was found in 26.9% of patients with nocturia (391/1452) and 25.6% of patients without nocturia (505/1975).
Provoked detrusor overactivity was observed more frequently in patients with nocturia (13.5% [196/1452] vs 9.3% [184/1975]), as was systolic detrusor overactivity (11.2% [162/1452] vs 9.3% [183/1975]). Low bladder compliance was more prevalent in patients with nocturia (23.6% [343/1452] vs 18.3% [361/1975]).
No meaningful differences were observed in urgency (4.5% [66/1452] vs 3.5% [70/1975]), and voiding dysfunction (9.2% [134/1452] vs 8.1% [159/1975]). Pelvic organ prolapse was slightly less common in patients with nocturia (3.7% [54/1452] vs 4.5% [88/1975]).
Normal urodynamic findings were less frequent in patients with nocturia (15.2% [221/1452] vs 22.3% [441/1975]).
Patients with nocturia were more likely to have overactive bladder symptoms, 78.9% experience this issue (1145/1452), compared to 32% of those without nocturia (636/1975). Similarly, bladder pain was more common for patients with nocturia, affecting 97% of them (1404/1452), whereas 53% of patients (1048/1975) without nocturia had this issue.
Interpretation of results
The differences in some urodynamic measurements between groups were relatively small, but statistically significant. Notably, patients with nocturia were more likely to have abnormal urodynamic findings. This suggests that nocturia is a complex symptom that can be caused by different underlying problems.