This study presented the first nation-wide report on prevalence of nocturia (at least one void at night) in a multiracial population of Malaysia. The overall prevalence of nocturia among Malaysian adults was high (57%), which was comparable with those reported from studies in Asian population, yet relatively higher compared to Western populations. Liew and colleagues reported that the prevalence of nocturia among Singaporean adults was 55% [13]. Meanwhile, the reported prevalence were 46% in the Dutch population [14], 31% in the US population [5] and 28.4% in the Turkish population [15]. In the present study, there was a significant higher prevalence among women. This finding is consistent with the report from previous studies [13, 14, 16, 17]. Nevertheless, information on the exact etiology pertaining to high prevalence of nocturia in women is lacking. Nocturia was found to be more common among younger women (18–40 years old). This is congruent with the finding from study in Finland [17].
In addition, the prevalence of nocturia was found to increase with age, which corroborated the findings of other studies [4, 5, 18]. This may be due to various pathophysiological mechanisms that related to ageing. In the elderly, nocturia can be resulted from decline in functional bladder capacity with high post void residual, deregulation of arginine vasopressin level, sleep disorders and comorbidities including diabetes mellitus and diabetes insipidus [19]. This also further explains the finding in current study that the frequency of nocturnal voids was higher among the elderly population than younger population. On the other hand, there was higher nocturia prevalence among those 31–40 years old than those between 41 and 50 years old. The underlying etiology for this finding is unknown, but it may be due to the alcoholic beverage consumption among this age group. Based on the previous National Health and Morbidity Survey 2011 in Malaysia, those 30–39 years old presented with highest prevalence of alcohol consumption than other age groups and the drinking pattern waned by older population [20]. Nevertheless, further investigation is required to reveal the exact etiology of this finding.
Previous studies have reported the differences in prevalence of nocturia among races in the US population. The prevalence of nocturia was reported to be higher among Black and Hispanic respondents compared to the White respondents [21, 22]. Consistently, similar observation was reported among the multi-ethnic groups in Malaysia. Malay respondents had a significant higher prevalence compared to other races as revealed by the univariate analysis, yet this prevalence was not significant in multivariate analysis. Chinese and Indian respondents on the other hand, had significantly lower prevalence compared to Malay in both univariate and multivariate analyses. However, Liew and colleagues reported that there was no significant difference between Malay, Chinese and Indian respondents in Singapore [13]. Kupelian and colleagues reported that socioeconomic status was accounted for the ethnic discrepancies in prevalence of nocturia [22]. Further investigation is required in order to identify the underlying etiology of ethnic discrepancies among Malaysians in term of prevalence of nocturia.
Nocturia is strongly associated with various risk factors and comorbidities, including cardiovascular diseases, diabetes, sleep disorders, somatic and mental health [6, 13, 18, 23, 24]. This supports the findings of this study which also showed the significant higher disease prevalence among respondents with comorbidities such as hypertension, diabetes mellitus, renal disease or overactive bladder. The pathophysiological changes in hypertensive patients appear to be a significant risk factor for nocturia [25, 26]. A prolonged hyperglycemic state in diabetes mellitus patients on the other hand, may cause an alteration in urinary bladder activity, predisposing to diabetic cystopathy [27]. Diabetic cystopathy is primarily induced by paralysis of detrusor muscle and hyperglycemia-induced polyuria that can further lead to bladder hypertrophy in patients with diabetes mellitus [27]. Moreover, microvascular complications of diabetes, particularly diabetic nephropathy and neuropathy have been implicated in nocturia [28]. Diabetic nephropathy is associated with polyuria and an increase in mean void volume, whereas, diabetic neuropathy may lead to impaired bladder sensation, poor detrusor contractility and increased post void residual [28]. This explains the mechanistic link between diabetes mellitus and nocturia.
Several studies have reported that nocturia is associated with chronic kidney disease [13, 29, 30]. This may be attributed to the failure of kidneys to concentrate the urine as the renal function worsens, and ultimately leads to nocturnal polyuria and increased nocturnal urine volume in patients with chronic kidney disease [31]. Additionally, overactive bladder was also found to be one of the risk factors in this study. Indeed, nocturia is a common urinary symptom in overactive bladder patients [32]. However, in this study, there was no significant association between nocturia and benign prostatic hyperplasia, prostate cancer, bladder cancer and snoring, which had been reported in previous studies [22, 23, 33]. This could be due to the comorbidities determined by self-reporting of respondents in the present study, which might have led to underestimation of the prevalence of these comorbidities in Malaysia.
Excessive evening intake of fluid, caffeinated drinks or alcohol is known to be one of the causes of nocturnal polyuria [1]. In the current study, approximately one third of the respondents with nocturia have the habit of consuming large volume of water, tea or coffee in the late evening. This may suggest that limiting fluid or caffeinated drink intake in the late evening among Malaysian could be one of the modifiable lifestyle risk factors for nocturia. Shiri and colleagues reported that there was no significant association between coffee consumption and nocturia among 50 to 70 years old men in Finland, yet the risk of moderate or severe nocturia was twofold higher among men who drank 6 cups coffee or more per day than non-drinkers or those who consumed one cup per day for this age group [34]. Interestingly, the prevalence of nocturia was about one third of respondent despite any drink consumption. The actual prevalence of nocturia with underlying pathological causes in the population may be reflected by eliminating the potential confounding factor of drink consumption in the late evening.
LUTS can be classified according to voiding or obstructive symptoms (such as hesitancy, poor stream, straining, prolonged micturition, feeling of incomplete bladder emptying, post-micturition dribble) and storage or irritative symptoms (such as frequency, urgency, urge incontinence and nocturia). In the present study, the disease pattern of nocturia was not sex-specific, except for post-micturition dribble. This interpretation is supported by the fact that post-micturition dribble is more common in men [35]. Studies also showed that prevalence of LUTS was comparable between men and women [36, 37]. In addition, with advancing age, the prevalence and severity of LUTS increase regardless of sex [36]. This is supported by the finding of this study where elderly respondents are more likely to exhibit almost all the LUTS compared to the younger population.
Nocturia has been regarded as not only ‘bothersome’, but also negatively affects sleep and quality of life [5,6,7,8]. This study also revealed that nocturia was regarded as moderately bothersome for Malaysians, particularly those with two or more nocturnal voids. This alluded to the clinical relevance of at least 2 voids being the threshold to patient-reported impaired health-related quality of life [38]. Furthermore, more than one-third of respondents in this study claimed to have disturbed sleep about half the time or more after nocturnal awakening. The sleep disturbance was proportionately increased with the frequency of nocturnal voids and age. This finding is consistent with previous studies [5, 13, 14, 39]. As a result of sleep disturbance, nocturia has also been associated with excessive daytime sleepiness (7–18%), increased sick leaves (27–27%), insomnia (43%), psychiatric disorders (28–35%) and poorer health status (15–40%) [40, 41] In addition, people with nocturia have a lower productivity at work and decreased activity levels [6]. Consistently, the respondents with nocturia in this study also reported to experience fatigue, difficulty in concentrating, lacking of motivation to work, bad mood, forgetfulness and depression as consequences of disturbed sleep. Hence, it is obvious that nocturia should not be overlooked or underestimated due to its serious repercussions on sleep quality, work productivity and quality of life.
Treatment-seeking behaviour for LUTS is correlated with the symptom severity, degree of bother, costs and benefits of treatment [42, 43]. Consistently, this study found that those who had not sought treatment were presented with less than two nocturnal voids, less degree of sleep disturbance and lower bother score as compared to those who had sought treatment. To the best of our knowledge, this is the first study to report on the association between awareness of nocturia and treatment-seeking behaviour in Malaysia. Approximately two-thirds of respondents with nocturia in this study were not aware that nocturia is a medical condition and this was significantly associated with behaviour of not seeking medical attention. This finding suggests that poor awareness might be a factor affecting their treatment-seeking behaviour. In Taiwan, Chen and colleagues found that the lack of knowledge on nocturia appeared to be an important barrier to medical consultation among Taiwanese women [9]. In addition, a vast majority of those who had not sought treatment in the present study perceived that nocturia was not a significant medical issue to seek treatment. This appears consistent with finding by Low and colleagues who reported that majority of women in Northern Malaysia did not seek treatment for LUTS due to low level of disease awareness [11]. These findings could be attributed to poor knowledge pertaining to nocturia among Malaysians. As such, addressing the misconceptions about nocturia can help to increase the awareness, enhance treatment-seeking behaviour and also improve the overall quality of life among people with nocturia. Interestingly, this study revealed that most women did not seek treatment for nocturia as compared to men. This is in contrast with the finding from a study conducted in the primary care setting in Malaysia, which revealed the higher tendency for women to seek treatment when compared to men [44]. Further investigation is required to identify the sex difference in treatment-seeking behaviour among nocturia patients.
In the present study, convenience sampling was conducted instead of stratified sampling to define the population in Malaysia. Despite this limitation, the pool of subjects sampled were closely reflecting the real population in Malaysia. Although there was slightly difference between the sample and population in terms of age and sex, these differences were adjusted in the statistical analysis. Hence, the outcomes of this study are valuable to provide sights into prevalence of nocturia among Malaysians.