Most previous studies on nocturia have focused on men older than 50 years. In the present study, we recruited younger men because they have rarely been investigated in the literature. Moreover, we could avoid causes of nocturia from organic diseases of the lower urinary tract, such as benign prostate hyperplasia, which are infrequent among younger men. Based on the results of the online questionnaire survey, we found that the prevalence of nocturia in Asian adult males younger than 40 years of age was 8%. This finding is consistent with other studies. The reported prevalence rate of 2 or more voids per night ranged from 2–16.6%9. Thus, our study sample recruited from Facebook could be representative of younger men in the general population.
Other studies including younger and older adults have revealed that increased age and BMI were both risk factors for nocturia. Madhu et al.10 conducted a secondary analysis of the EpiLUTS data using participants with nocturia. Age, BMI, anxiety, depression, and a history of bed-wetting were significantly associated with nocturia. Fitzgerald et al.2 found that the odds ratio of nocturia increased with age and BMI in a multivariate model. Other studies also reported that nocturia was significantly associated with obesity11,12. Similarly, in the present study, age older than 30 years, BMI over 25 kg/m2, and presence of moderate to severe LUTS were predictive factors for nocturia in our sample of young Asian men. Goessaert et al.13 found that reduced functional bladder capacity was associated with nocturia in younger participants, which would deteriorate with aging. Obesity would increase the intra-abdominal pressure and lead to nocturia14. In addition, those with obesity would have a higher chance of obstructive sleep apnea, resulting in nocturnal polyuria and detrusor instability15,16. One supportive evidence in our study is that the participants with nocturia had a higher IPSS, especially storage scores. This relationship has been found to be more profound in men17 and younger patients18,19, similar to our study population.
One of the key findings of the present study was the association between nocturia and the level of depression in young men. Our findings are compatible with previous findings. Asplund et al.20 found that major depression was associated with a six-fold increase in nocturia in men. A cohort study by Johnson et al.21 showed depressed and nondepressed patients reported a mean of 2.7 and 1.9 episodes of nocturia per night, respectively. Patients with 5 or more episodes of nocturia per night experienced a 6.5-fold increased risk of depression. Häkkinen et al.3 noted a unidirectional effect of depressive symptoms on the incidence of moderate or severe nocturia. A systematic review concluded a bidirectional association between depression and nocturia: nocturia increased the odds ratio of depression (OR 1.2–20.24), while depression similarly increased the odds ratio of nocturia (OR 1.2–7.73)4. Our findings not only support the association between depressive symptoms and nocturia, but also indicate the association is likely a severity-dependent tendency, because the more severe the depressive symptoms, the greater the odds ratio to have nocturia, as indicated by the univariate analysis. Furthermore, we provide evidence in the multivariate model II analysis that the association of depressive symptoms with nocturia was because of depression-associated somatic symptoms. The association between levels of depression-related somatic symptoms and nocturia provides clinicians insight into the possible underlying correlates for the relationship of depression with nocturia.
There are several potential mechanisms underlying the relationship between depression and nocturia. One possibility is through poor sleep quality. Nocturia has been shown to have close relationships with early wake-ups and decreased total sleep time22. In a cohort of patients treated for depression, depression severity significantly correlated with sleep quality23. Przydacz et al.24 even argued that it is not depression severity, rather it is sleep quality that correlates with nocturia. Second, depression has been shown to have a negative effect on perception, development, and prolongation of LUTS, including nocturia25. Third, depression may involve both increased nocturnal diuresis via a disturbed 24-hour rhythm of antidiuretic hormone secretion, and a decrease in nocturnal bladder capacity through a central and/or peripheral serotonergic effect20. Fourth, in a previous study26, patients being treated with selective serotonin-reuptake inhibitors for depression had twice the incidence of nocturia. Another study27 also showed that the incidence and severity of overactive bladder, whose symptoms include nocturia, increased in men using antidepressants.
In the present study, we found that TDQ score was independently associated with nocturia. Moreover, it was somatic rather than affective/cognitive symptoms that related to nocturia. One possible explanation is the different expression of depression in different cultures. For example, Vietnamese patients were prone to endorse higher levels of somatic symptoms than German patients despite similar levels of depression severity28. Similarly, somatic complaints predicted depression in Vietnamese and Vietnamese American adolescents, whereas no relationship was found in European American adolescents29. Furthermore, those with normal-high TDQ scores had the highest odds ratio to develop nocturia. Thus, the complaints of nocturia in young Asian males could be a red flag signaling a depressive mood, which could progress to major depressive disorder without early intervention. Therefore, by utilizing a culturally-relevant depression screening instrument, such as the Taiwanese Depression Questionnaire, with young male patients complaining of nocturia in urology clinics, it would be possible to identify early on those who are at risk of developing a depressive disorder.
There are several limitations to this study that should be mentioned. First, this study recruited participants from a social media site (i.e., Facebook) as opposed to a community-based population. As such, selection bias may exist. Second, we did not investigate comorbidities, medical history, diet, physical activity, or psychiatric history of the participants, which may also have an influence on the occurrence of nocturia. Third, the information from a 24-hour voiding diary is nearly impossible to get from an online survey, which could help determine the etiology of nocturia. Nevertheless, there are some advantages of the present study. We recruited more than 3,000 young men; a population that has been less investigated for LUTS including nocturia. We focused on young men instead of older adult men because they would have less comorbidities and less medications related to nocturia, and therefore, less confounding factors. We also evaluated the associations between depression and nocturia with a culturally-relevant questionnaire. The findings of the present study have practical implications for urologists when treating young men with nocturia. Early assessment of depressive symptoms can be preventative by making a referral for psychological evaluation and treatment of psychological symptoms.