Insomnia and nocturia are prevalent and highly comorbid conditions, both showing signs of an impaired circadian rhythm and affecting sleep in a heterogeneous population [1,2], yet research regarding both remains rather scarce. Addressing both conditions together could lead to a better understanding of the underlying mechanism of nocturia in patients with insomnia. In order to summarize existing relevant literature, we performed a systematic review with meta-analysis on the topic, regarding one: the prevalence of nocturia in patients with insomnia, two: report on the sleep characteristics of insomniacs with and without nocturia, three: interventions for treatment of insomnia and their effect on nocturia.

A systematic review of literature was performed through EMBASE, MEDLINE, CLINICALTRIALS.GOV and CENTRAL databases up until November 2022 according to the Preferred Reporting Items for Systematic Review and Meta-analysis (PRISMA) statement. Studies reporting on a nocturia in patients with insomnia were included. Insomnia was defined as difficulty initiating or maintaining sleep or suffer from early morning awaking (DSM) [1] or based on validated questionnaires such as the Insomnia Severity Index (ISI) [26]. The definition of nocturia was accepted based on the ICS definition, waking up to void during the main sleeping period. From the identified reports, 11 studies were retained, of which 7 were eligible for meta-analysis. A forest plot demonstrating the pooled OR of nocturia in a population of insomniacs was created for graphic illustration. Bias assessment was performed using the ROBINS tools as per the Cochrane collaboration guidelines.

Seven out the of 11 included studies reported on the prevalence of insomnia in relation to nocturia. A total of 5396 middle-aged to elderly people, of which 47.5% women, were included in the meta-analysis. According to the meta-analysis, the pooled estimate OR for nocturia in patients with insomnia was 1.958 (95% CI: 1.609–2.384) based on the seven studies in a random effects model with non-significant heterogeneity (I² = 50.83%, p=0.06) (Table 1). The visual representation in the forest plot clearly shows a significant overall higher odds of reporting nocturia in case of concomitant insomnia (Figure 1).  Wake after sleep onset (WASO) was longer in people with insomnia and nocturia compared to those without and sleep efficiency (SE) declined. Interventions with melatonin, diet and behavioral therapy showed a beneficial effect on nocturia frequency in patients with insomnia.

The data demonstrates that nocturia is a prevalent condition in people with insomnia. Sleep characteristics of elderly male and female insomniacs with and without nocturia show observations in line with the expected. More and longer nocturnal awakenings, worse SE and longer WASO. Only 3 interventional studies concerning behavioural treatment, diet and melatonin for the treatment of insomnia looked at the effect on nocturia. All 3 interventions reduced the number of nocturia episodes significantly, amplifying the hypothesis of a bidirectional relationship between nocturia and insomnia. These results highlight the importance of actively question and treat nocturia accordingly when people complain of insomnia in order to improve their overall sleep quality. Our analysis was based on the scarcity of the available data, but we acknowledge the existence of an important selection bias as a limiting factor to the generalizability of our results. Nevertheless, the current analysis provides information on nocturia in a middle-aged to elderly population with insomnia, which is also the population in which both conditions remain highly prevalent and hence, clinically relevant. We advocate for further retrospective and prospective research regarding nocturia in people with insomnia throughout all age groups, using appropriate definitions and validated questionnaires.

To our knowledge this is the first systematic review and meta-analysis assessing the effect of nocturia in people suffering from insomnia. The overall odds for nocturia in a middle aged to elderly insomnia population is visibly higher in patients with insomnia than those without and causes worse sleep outcomes. Interventions for treating insomnia such as melatonin, behavioural therapy and dietary adjustments show beneficial results on nocturnal voiding frequency. This systematic review does have several limitations such as data heterogeneity, confounding, patient selection and measurement bias. However, our study reveals a significant research gap, hence we advocate for further research regarding nocturia and insomnia in which LUTS complaints are addressed and appropriate definitions and questionnaires are being used. Routine screening for nocturia in patients with insomnia should be implemented in order to maximize sleep quality improvement.

Morin CM, Benca R. Chronic insomnia. The Lancet 2012;379:1129–41. https://doi.org/10.1016/S0140-6736(11)60750-2.
Kido K, Hatakeyama S, Imai A, Yamamoto H, Tobisawa Y, Yoneyama T, et al. Sleep Disturbance Has a Higher Impact on General and Mental Quality of Life Reduction than Nocturia: Results from the Community Health Survey in Japan. Eur Urol Focus 2019;5:1120–6. https://doi.org/10.1016/J.EUF.2018.04.017.
American Psychiatric Association. Diagnostic And Statistical Manual Of Mental Disorders, 5th Edition: DSM-5. n.d.

Continence 12S (2024) 101412
DOI: 10.1016/j.cont.2024.101412