Overactive bladder (OAB) is a bladder-centric syndrome that consists of urinary urgency with or without urge urinary incontinence, often accompanied by frequency and nocturia [1]. The prevalence of OAB ranges from 7% to 27% in men and 9% to 43% in women; its prevalence tends to increase with age [2]. OAB-induced impairment of quality of life has been well documented, and OAB weakens physical, emotional, social, and mental functioning [3]. OAB may lead to isolation, embarrassment, reduced contact with family and friends, loss of confidence or motivation, sexual dysfunction, and hopelessness. As a result, OAB may advance some symptoms of depression.

Sleep is a major component of mental and physical health [4]. Sleep problems were found to be associated with poor social interaction, diminished work productivity and work quality, and lower overall quality of life. Numerous studies have linked lower urinary tract symptoms to sleep disturbance [5-7]. Both storage and voiding lower urinary tract symptoms were found to be independent predictors of sleep dysfunction. However, research has been limited regarding the possible correlation between OAB and sleep disorders [8,9], although the relationship between nocturia, an OAB symptom, and sleep problems has been examined extensively [10,11]. The relationship between OAB and sleep complaints, therefore, is not well understood and warrants additional investigation [12]. Importantly, thus far, investigators have examined only the general population (i.e., mentally healthy persons without diagnoses of depression or other psychiatric disorders). The association between OAB and sleep quality has not been assessed in detail for most specific patient subpopulations, although clinicians could better serve some of their patients if they were armed with information about the possible association between urinary tract symptoms, including OAB, and sleep quality [13].

Patients with depression represent a uniquely important population because of a possible bidirectional relationship between OAB and depression [14,15]. This bidirectional relationship should encourage the multidisciplinary management of patients with depression coordinated by psychiatrists and urologists. However, until now, the medical community has not investigated the impact of OAB on sleep quality in patients with depression. Even though current recommendations underscore the need for sleep assessment of OAB patients, it is still unknown whether OAB is correlated with sleep quality in patients treated for depression. This data vacuum may lead to a hypothesis that the coexistence of OAB and sleep dysfunction in depressed patients might be more complex, underreported, and undertreated. These absent data are necessary to provide a more comprehensive understanding of the clinical workup and integrated care that depressed patients need. Moreover, the sleep quality of patients with depression may be independently decreased by depression itself. Thus, the aim of this study was to investigate connections between OAB and sleep quality in patients with depression. We hypothesized that patients with depression who reported OAB symptoms experienced greater sleep impairment than patients with depression who did not have OAB symptoms.

Between 2014 and 2015, adult patients treated in our outpatient and inpatient department of adult psychiatry were prospectively recruited for this study. We assessed the severity of their depression, sleep disturbances, and OAB symptoms. All the included patients met both the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) and International Classification of Diseases, 10th Revision (ICD-10) criteria for depression, and psychiatrists established the diagnoses of all patients. The following demographic data were considered a priori: age, sex, education, employment status, relationship, recent hospitalizations due to depression, familial history of depression, and depression medications.

Patients with lower urinary tract symptoms, including OAB, are thought to experience higher rates of sleep disturbance than the general population. Our study was the first to analyze the impact of OAB symptoms on sleep quality in a unique patient population reliably diagnosed with, and treated for, depression. Almost 13% of patients with our depression in our cohort reached the diagnostic threshold of OAB using the validated ICIQ-OAB instrument. Thus, OAB symptoms may be present in a substantial percentage of patients with depression receiving routine psychiatric treatment. Further, sleep quality analyzed with 2 independent validated questionnaires (i.e., the HSDQ and AIS) was correlated with OAB. These disorders and symptoms tended to coexist and likely compounded the severity of each another. This coexistence property should prompt a re‐ evaluation of current recommendations on diagnosis of sleep problems for patients with depression [22,23]. Depressed patients, primarily those reporting sleep problems, should be screened carefully for OAB symptoms. Psychiatrists may have limited perception of lower urinary tract symptoms, including OAB, in their patient populations [24]; thus, complex management of this patient group, particularly by cooperation between psychiatrists and urologists, should be a priority among healthcare professionals.

A strength of this study was the use of validated scales to assess depression severity, sleep quality, and OAB symptoms. These instruments were unlikely to cause under- or overreporting of urological and psychiatric symptoms and sleep problems. The use of 4 different reliable questionnaires, including 2 independent instruments for sleep quality assessment, provided accurate results. Unlike our analysis, some prior investigations that reported correlations between OAB and sleep in the general population did not use validated questionnaires [25,26]. It is strongly recommended to collectively assess OAB symptoms with appropriate instruments [27].

Another strength of our study was its analysis of a homogeneous group of patients with depression, all of whom met the DSM-5 and ICD-10 criteria for depression. In all cases, psychiatrists confirmed the diagnoses. Further, all were treated for depression. The study results, therefore, clearly showed the relationship between sleep quality and OAB symptoms in this specific patient group.

In the literature, a link between sleep quality and OAB has been reported. Ge et al. [8], in their cross-sectional analysis of 51 OAB patients and 30 age-matched controls, showed that sleep disturbances were associated with more severe OAB symptoms and poorer psychosocial health. Savoie et al. [9], in a prospective study of 161 women, demonstrated that OAB patients had high rates of poor sleep quality and sleep disruption, even in the absence of nocturnal bladder symptoms. Similarly, several epidemiological studies have presented a link between OAB and depressive symptoms, and they have even suggested a bidirectional nature of this relationship. The largest epidemiological investigations of lower urinary tract symptoms and OAB (NOBLE, EPIC, and EpiLUTS) demonstrated this interconnection [15]. However, those studies all included participants from only the general population. Diagnoses of depression were neither established nor confirmed by psychiatrists. The results were based solely on single, sometimes nonstandard instruments to assess depression. The measures used in studies that focused on the general population were used only to screen for depression, and they were not diagnostic even if they were effective in assessing symptom load [28]. Therefore, all these earlier studies, in fact, analyzed correlations between sleep quality and OAB in the general population or, at best, in patients with depressive symptoms, but not necessarily depression. Until now, it was questionable whether any relationship exists between OAB symptoms, sleep quality, and reliably diagnosed depression. Our study has established this relationship.

Nocturia needs special consideration. Studies of the general population showed that 2 episodes of nocturia is a threshold for bother [29]. One nightly void did not appear to be sufficiently disruptive to cause significant bother for most patients. However, this 2-episode threshold is not recommended for all patient populations [29]. In our study, at least 3 episodes of nocturia were necessary to significantly lower sleep quality in individuals with depression. We speculate that patients with depression have a greater tolerance for nocturia. We also found that nocturia may not be the only significant predictor of sleep disturbances because other OAB symptoms also contributed to impaired sleep patterns.

The pathophysiology responsible for the negative effects of OAB on sleep quality is not well understood. First, nocturia, an OAB symptom, substantially deteriorates sleep quality. Nocturia-induced sleep fragmentation causes daytime drowsiness, poor concentration, and anxiety, which leads to impaired occupational functioning and physical and emotional health, ultimately degrading an individual’s quality of life [30]. Second, obstructive sleep apnea, a disorder with repeated episodes of complete or partial obstruction of the upper airway during sleep, was also linked to OAB (mainly to nocturia and urgency) and poor sleep quality [31]. Obstructive sleep apnea may lead to increased secretion of atrial natriuretic peptide in response to airway obstruction, thereby causing nocturnal polyuria. Animal studies also showed that hypoxia induced by obstructive sleep apnea was associated with bladder oxidative stress, altered cell signaling, and structural damage, finally leading to increased urinary frequency and involuntary bladder contractions [32]. Notably, in our cohort, no patient was diagnosed with obstructive sleep apnea. Third, another hypothesis is that central sensitization with spinal hypersensitivity may lead to a variety of chronic pain disorders that share some pathophysiological pathways with OAB [33]. Finally, the increased presence of non-urologic symptoms in OAB patients suggests an underlying systemic etiology and pathogenetic mechanisms that may contribute to OAB. Differences have been observed between OAB and non-OAB patients across multiple organ systems, including neurological, cardiopulmonary, gastrointestinal, sexual, musculoskeletal, and gynecological systems [34]. About a third of OAB patients report widespread systemic symptoms, with a high symptom burden across multiple organ systems [34]. This multiorgan involvement suggests that correlation between OAB symptoms and sleep quality may be more complex than expected.

There are some potential weaknesses of our study. First, patients were not reliably diagnosed with OAB. An accurate diagnosis of OAB requires exclusion of urinary tract infection or other obvious pathologies. In addition, we did not collect data from voiding diaries. However, we assessed OAB symptoms using an instrument with an adequate threshold score that has been validated in other OAB studies. Second, we focused on the continuous variable of general sleep disorder from the HSDQ. We attempted to perform correlation analyses for each of the questionnaire clusters, which may have further differentiated various types of sleep disorders; however, using the HSDQ we were not able to identify consistent relationships between specific types of sleep disorders and OAB. Although our sample size was large enough for a powerful statistical analysis, the study may have lacked adequate power for specific and detailed analyses. Third, we were not able to longitudinally assess our patients. It is an open question whether OAB-specific treatments, including physiotherapy, patient education, and pharmacotherapy, would improve sleep quality in this specific patient group. In the general population, sleep quality improved after OAB therapies such as anticholinergics or sacral neuromodulation [35]. Nonetheless, we used data obtained from a prospectively maintained database. Finally, we acknowledge that the patients evaluated were a highly selected cohort, treated at a single, high-volume academic center; our findings could have been somewhat different if we had assessed a less highly selected cohort of patients treated for depression.

In conclusion, this study of a carefully constructed cohort has shown a link between OAB symptoms in patients with depression and sleep quality. OAB symptoms were present in a substantial percentage of our cohort of patients who had been diagnosed with, and were receiving treatment for, depression. We also found a strong correlation between OAB symptoms and sleep quality. Therefore, healthcare professionals who treat patients with depression should screen for both sleep problems and OAB symptoms. We suggest that our study will promote improved patient-centered care of individuals with depression.