Though not previously formally studied, the causes of nocturia may be accompanied by differing symptoms and risk factors. We hypothesised that clinical features may help distinguish patients with nocturia. This study aimed to characterise predictors of detrusor underactivity (DU), overactivity (DO), and bladder outlet obstruction (BOO), confirmed on urodynamics studies (UDS), in males and females presenting with nocturia.

This was a retrospective study of consecutive patients referred for UDS over a seven-year period, at a single-centre tertiary institution. Adult males and females who had nocturia (≥2 times per night) at time of UDS were included for analysis. Those with insufficient data collection were excluded from this study. Age, past medical history, quantity and type of storage and voiding symptoms, and UDS parameters were collected. DO, DU, and BOO diagnoses were documented based on the calculated parameters from UDS. For each gender, DO/DU/BOO were compared against baseline variables, and symptoms using chi-square and Wilcoxon rank sum tests. Multivariate logistic regression models were fit for covariates to support findings and create predictive probability models.

Altogether, 372 patients were included for analysis (158 men, 210 women). There was a higher proportion of men, compared to women, with DO (123/158 vs 125/210, p<0.001) and BOO (57/158 vs 14/210, p<0.001) confirmed on UDS. There was a similar proportion of men and women with nocturia who had confirmed DU (58/158 vs 98/210, p=0.197). Univariate analyses were performed for DO, DU and BOO, for each gender. For women, greater number of concurrent storage symptoms was associated with DO (p<0.001), while for men, more concurrent storage (p=0.008) and less concurrent voiding symptoms (p<0.001) were associated with DO. For women, older age (p<0.001) and a neurogenic bladder history (p=0.018) were associated with DU, in addition to concurrent voiding symptoms (p=0.009). For men, DU was associated with less storage (p=0.001) and more voiding symptoms (p<0.001). Although history of diabetes (p=0.039) and more voiding symptoms (p=0.003) predicted BOO in women, there was insufficient evidence to suggest association between storage (p=0.748) or voiding symptoms (p=0.568) and the presence of BOO in men. Regression models were fit for all significant covariates and confirmed their associations while adjusting for confounders and interactions.

There is strong evidence for a demonstrated effect of concurrent storage and or voiding symptoms, for predicting likelihood of DO, DU and BOO confirmed on UDS, for patients with nocturia. In addition, age and select medical history may also predict diagnoses, including diabetic and neurogenic bladder history.

It may often be difficult to distinguish the underlying aetiologies of nocturia as a presenting symptom. This study suggests concurrent voiding and storage symptoms, in addition to age and medical history, are useful for differentiating causes of nocturia in men and women.