Differences in characteristics of nocturnal enuresis between children and adolescents: a critical appraisal from a large epidemiological study

Authors

  • CHUNG K. YEUNG,

    1. Department of Surgery, Division of Paediatric Surgery and Paediatric Urology, and Centre for Clinical Trials and Epidemiological Research, Chinese University of Hong Kong, Prince of Wales Hospital, Hong Kong
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  • BIJI SREEDHAR,

    1. Department of Surgery, Division of Paediatric Surgery and Paediatric Urology, and Centre for Clinical Trials and Epidemiological Research, Chinese University of Hong Kong, Prince of Wales Hospital, Hong Kong
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  • JENNIFER D.Y. SIHOE,

    1. Department of Surgery, Division of Paediatric Surgery and Paediatric Urology, and Centre for Clinical Trials and Epidemiological Research, Chinese University of Hong Kong, Prince of Wales Hospital, Hong Kong
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  • FRANCES K.Y. SIT,

    1. Department of Surgery, Division of Paediatric Surgery and Paediatric Urology, and Centre for Clinical Trials and Epidemiological Research, Chinese University of Hong Kong, Prince of Wales Hospital, Hong Kong
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  • JOSEPH LAU

    1. Department of Surgery, Division of Paediatric Surgery and Paediatric Urology, and Centre for Clinical Trials and Epidemiological Research, Chinese University of Hong Kong, Prince of Wales Hospital, Hong Kong
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Chung K. Yeung, Chief, Division of Paediatric Surgery and Paediatric Urology, Department of Surgery, Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, NT, Hong Kong, SAR, China. e-mail: ckyeung@surgery.cuhk.edu.hk

Abstract

OBJECTIVE

To evaluate any differences in the characteristics of primary nocturnal enuresis (PNE) between younger enuretic children and adolescents.

SUBJECTS AND METHODS

In all, 21 000 questionnaires designed to determine the presence or absence of bed-wetting, diurnal incontinence, frequency of wetting, systemic illness, and family history, were sent to children aged 5–19 years from 67 kindergartens, primary schools and secondary schools randomly selected by a computer from different areas in Hong Kong. In addition, questions were asked to evaluate when and how the parents became aware that bed-wetting is a significant medical problem deserving attention in children after the age of 5 years.

RESULTS

Of the 21 000 questionnaires distributed, 16 512 (78.6%) were completed. Among the respondents, 512 children (302 boys, 210 girls) had PNE; of these, 106 (20.7%) also had daytime incontinence. There was a marked reduction in the overall prevalence of PNE with advancing age. At 5 years old, 16.1% of children had PNE (20.7% boys, 10.8% girls; at age 9 and 19 years, 3.14% and 2.2% of children had PNE, respectively. However, this reduction was significantly more apparent among those with mild enuretic symptoms (wet <3 nights/week) than in those with more frequent bed-wetting. Furthermore, younger enuretic children behaved very differently from adolescents and older patients. As age increased there was a significant tendency towards more severe enuretic symptoms. At age 5 years, 14.3% of enuretic children wet 7 nights/week, compared with 48.3% at age 19 years (P < 0.001). In addition, significantly more adolescent boys aged >10 years had daytime urinary incontinence than had enuretic children aged ≤ 10 years (32% vs 14.6%, respectively, P < 0.001). Most (89%) parents only became aware that bed-wetting was a significant medical problem deserving attention through material in the mass media over the past 3–4 years.

CONCLUSIONS

The present finding suggesting that PNE spontaneously resolves with increasing age probably applies only to those with mild enuretic symptoms. There are significant differences in characteristics between younger enuretic children and older subjects. As age increases there is an increasing proportion of enuretic patients with more severe bed-wetting. Enuretic children aged >10 years and adolescents have significantly more daytime urinary symptoms and incontinence. The previously reported low prevalence of PNE in Hong Kong was probably due to parental indifference to the problem.

Abbreviations
PNE

primary nocturnal enuresis.

INTRODUCTION

Primary nocturnal enuresis (PNE), or bed-wetting, is a very common clinical and a significant social problem in childhood and adolescence. From published epidemiological studies it is apparent that although the values vary somewhat among different countries, the overall prevalence of PNE remains relatively constant, irrespective of geographical locations. It was estimated that 20–25% of children by the age of 4 years and 10% of children at 7 years are frequent bed-wetters [1–5]. In general, the prevalence decreases with increasing age. However, the condition often has a profound psychological and social impact on the affected children and their families, and generates significant anxiety and even conflicts among them.

A previous epidemiological survey for PNE in Hong Kong in 1995 indicated that the prevalence of PNE in local Chinese school children was surprisingly lower than all reported series from elsewhere [6]. Since then, public educational programmes both in Hong Kong and in surrounding Asian countries have been introduced. In addition, mass screening for PNE in Hong Kong through the local Student Health Service has been implemented. Concurrently, in a tertiary referral centre for PNE, we have seen a rapid increase in severely enuretic children, many of whom have never been regarded by their parents as having a medical problem until very recently. Similarly, results of the subsequent epidemiological studies in other Asian countries indicate a much higher prevalence of PNE than that reported previously in Hong Kong, and were similar to values reported in other western countries. To re-evaluate the actual prevalence of PNE among local children, a repeat epidemiological study involving a much larger sample was therefore conducted.

SUBJECTS AND METHODS

Children aged 5–19 years from 67 kindergartens, primary schools and secondary schools, with a greater emphasis on adolescents and teenage groups, were randomly selected among different areas of Hong Kong. A self-administered questionnaire comprising two sections, identical to that used in our previous study, was designed [6]. The first part of the questionnaire determined the demographic details, e.g. age, sex, and family history of enuresis; the second part included questions about the details of bed-wetting problems, if any. Questions included were the presence of daytime wetting, night-time wetting and frequency of wetting. In addition, questions were set to ask the parents when and how they became aware that bed-wetting was a significant medical problem that deserves attention in children after the age of 5 years.

Based on findings from our previous epidemiological study, and given an expectation that up to 2.5–3% of children and adolescents in Hong Kong are likely to have PNE, 21 000 questionnaires were sent to different schools, to ensure an adequate number of enuretic subjects for further statistical analysis. Sealed envelopes were provided to return the questionnaires and to ensure confidentiality. An information leaflet was attached to the questionnaire informing the parent of the voluntary nature of the study. All unreturned and incomplete responses were considered as nonresponders. Enuresis was defined as having at least one wet night every 3 months, as described previously [6]. To evaluate the factors associated with the severity of enuresis, subjects with enuresis were stratified by age. The frequency of bed-wetting was divided into three severity subgroups as <3, 3–6 or 7 wet nights/week, respectively.

The chi-square exact probability test was used to compare the prevalence in PNE between boys and girls in corresponding age groups, and to compare the severity of PNE and associated day symptoms in children and adolescents. To identify significant differences in the prevalence of PNE in boys and girls between different age groups, the chi-square test for trend was used, with P < 0.05 considered to indicate statistical significance.

RESULTS

Of the 21 000 questionnaires distributed, 16 512 (78.6%) were completed, from 7455 (45.1%) boys and 9057 (54.9%) girls (mean age 13.68 years). Among these, 512 children had PNE, giving an overall prevalence of 3.1% (4.0% boys and 2.31% girls); of these 512, 106 (20.7%) also had daytime urinary incontinence. There was a marked reduction in the overall prevalence of PNE with increasing age (Fig. 1). At age 5 years, 16.1% (20.7% boys, 10.8% girls) children had PNE, at 7 years, 10.1% (10.7% and 9.2%, respectively) and at 9 and 19 years, 3.14% and 2.2% had PNE, respectively (Table 1). Table 1 also shows that there was a significant and decreasing trend in the prevalence of PNE in both genders with age (both P < 0.001).

Figure 1.

Prevalence of PNE in Hong Kong schoolchildren.

Table 1.  The prevalence of PNE in Hong Kong school children
Age, yearsMaleFemaleTotalMean % (95% CI)
enuretics/normalenuretics/normalenuretics/normal
 5 48/232 22/203 70/43516.11 (12.6–19.50)
 6 38/212 20/236 58/44812.95 (9.8–16.10)
 7 36/335 23/249 59/58410.1 (7.7–12.5)
 8 19/244 17/342 36/586 6.14 (4.2–8.1)
 9 19/445  11/523 30/968 3.14 (2.0–4.2)
10  11/365 15/621 26/986 2.63 (1.6–3.6)
11 16/485  7/573 23/1058 2.17 (1.3–3.1)
12 15/433  5/554 20/987 2.02 (1.1–2.9)
13 10/506  6/520 16/1026 1.55 (0.8–2.3)
14  8/523  7/481 15/1004 1.49 (0.7–2.2)
15  7/621  8/546 15/1167 1.28 (0.6–1.9)
16 22/1014 16/1277 38/2291 1.65 (1.1–2.2)
17 20/803 17/1040 37/1843 2.0 (1.4–2.6)
18 19/768 21/1060 40/1828 2.19 (1.5–2.9)
19 14/469 15/832 29/1301 2.23 (1.4–3.0)
Total302/7455210/9057512/16512 3.10 (2.8–3.4)

Although there was a marked reduction in the overall prevalence of PNE with increasing age, it was significantly more apparent among those with mild enuretic symptoms (<3 wet nights/week) than in those with more frequent bed-wetting (Fig. 2). Overall, 82% of the adolescent subjects had >3 wet nights/week vs enuretic children aged 5–10 years (42.3%, P < 0.001, Table 2). As age increased there was a greater proportion of enuretic subjects with more severe bed-wetting. Daytime urinary incontinence was significantly more prevalent in adolescents than enuretic children (Table 2). Moreover, the prevalence of daytime urinary incontinence was significantly greater in adolescent boys than in boys aged 5–10 years (32% vs 14.6%, respectively, P < 0.001). In general, enuretic symptoms in the adolescent subjects were more severe than those in children. At age 5 years, only 14.3% of enuretic children wet 7 nights/week, compared with 48.3% at age 19 years (P < 0.001; Fig. 3).

Figure 2.

Severity of PNE in children.

Table 2.  The severity of NE in younger children and adolescents, and the incidence of daytime urinary incontinence in enuretic younger children and adolescents, as n (%)
ConditionChildren (5–10 years)Adolescents (>10 years)TotalP
Severity of PNE
<3 wet nights/week 161/279 (57.7) 42/233 (18.0)203/512<0.001
>3 wet nights/week 118/279 (42.3)191/233 (82.0)309/512<0.001
Daytime continence
Male 25/171 (14.6) 42/131 (32.1) 67/302<0.001
Female 13/108 (12.0) 26/102 (25.5) 39/210<0.001
Total 38/279(13.6) 68/233 (29.2)106/512<0.001
Figure 3.

Severity of PNE vs age.

Of the children with PNE, 39% considered that PNE was not a serious problem, while 61% of the children considered it as a serious problem with a significant impact on their daily life. Among these children, 28% became aware of this problem in the last 6 months, 21% had been aware for 1–2 years, 4% for 3–4 years and only 7% for >5 years.

DISCUSSION

Nocturnal enuresis is an old but still prevalent clinical problem in childhood and adolescence. The traditional view is that in most cases bed-wetting is due to a developmental immaturity of voiding control, and most enuretic children will ultimately acquire normal control with age. However, previous studies showed that, although spontaneous resolution can continue throughout childhood and adolescence, enuretic problems may persist in 1.5–3% of the adult population [7–10]. Previous studies also show that the frequency and severity of wetting episodes progressively increases with age; those with severe symptoms are much more likely to have persistent problems into adult life [11,12].

A previous epidemiological study for PNE in Hong Kong revealed a low prevalence in local Chinese schoolchildren; at 5 years old, only 10.4% of boys and 6.6% of girls had PNE. The prevalence decreased rapidly with increasing age and by 7 and 10 years old, only 4.9% and 1.2% of boys and 0.5% and no girls had enuresis, respectively [6]. These values were significantly lower than all previously published series from other countries [1–5,13–18].

Interestingly, most Chinese traditionally regarded faecal and/or urinary incontinence as normal for young infants and small children until the age of 4–5 years. Until recently, most people, and even medical practitioners, regarded bed-wetting as a normal phenomenon that does not warrant any intervention or treatment. Most parents would be reluctant to take a child with bed-wetting to seek medical advice until a very late age, and even if they do, the advice they receive from the medical practitioner most often would be simple observation, with a reassurance that the condition will disappear with time. This relative indifference or apathy within the Chinese community for PNE probably resulted in the low prevalence values reported in our previous epidemiological survey [6]. However, since the previous epidemiological study in the mid 1990s, an intensive public educational programme on NE has been introduced in Hong Kong, through a series of health talks, seminars, public lectures, featured articles, but most importantly via various mass media channels, including television and radio interviews, newspapers and magazines. In parallel with these there was a rapid increase in public awareness of PNE and the number of enuretic patients encountered in our clinic increased rapidly. Results from the present survey also show that more realistic epidemiological values can be obtained when the target study population has sufficient knowledge and interest in the problem, once misconceptions arising from traditional belief have been corrected.

The most important finding of the present study is that there were significant differences in characteristics between younger enuretic and older children. Although the overall prevalence of PNE decreased with increasing age, the proportion of patients with severe enuretic symptoms (wetting >3 nights/week) progressively increased. A significant proportion of adolescents (82%) had either moderate or severe enuresis, whereas most enuretic children (57.7%) have much milder bed-wetting with less than one enuretic episode/week. At age 5 years, only 14.3% of enuretic children wet 7 nights/week, compared with 48.3% at 19 years old (P < 0.001). Notably, the results of a previous epidemiological study of PNE in adolescents and adults up to the age of 40 years indicated that the prevalence of PNE remained rather static, with no further significant decrease after the age of 10 years, and >2% of both men and women remained enuretic. Of these affected adults, over half wet ≥ 3 nights/week, and a quarter had enuretic symptoms every night [10]. These findings therefore strongly suggest that the enuretic children with more severe symptoms probably have a significantly greater chance of persistent PNE in adult life. It is arguable therefore that for these groups of enuretic children with very severe symptoms, investigations and active treatments should be started at a much earlier age.

PNE is a heterogeneous disorder with various underlying pathophysiological mechanisms, causing in common a mismatch between the nocturnal bladder capacity and the amount of urine produced during sleep at night, in association with a simultaneous failure of conscious arousal, or waking, in response to the sensation of bladder fullness. Recent studies showed the important role of bladder dysfunction, e.g. small functional bladder capacity, instability during sleep, and detrusor hypercontractility caused by BOO, in the pathogenesis of PNE in children, especially those who are refractory to treatment [19–23]. Our previous epidemiological study of PNE in adolescents and adults showed a significantly higher incidence of urinary symptoms (frequency, urgency and incontinence), which were suggestive of underlying bladder dysfunction in adults with PNE, compared to normal controls [10]. Moreover, previous studies on bladder function in adult patients with PNE showed that the great majority (>90%) of adult enuretics had underlying detrusor overactivity, and 70% of the patients had urodynamic evidence of functional BOO [24]. This present study also showed that the incidence of daytime urinary symptoms was significantly higher in adolescents than younger enuretic children aged ≤ 10 years. The present finding suggesting that PNE will spontaneously resolve with age probably applies only to those with mild enuretic symptoms. Those with severe enuretic symptoms probably represent a more pronounced and refractory form of the condition, often associated with underlying bladder dysfunction, and would be more likely to have persistent enuretic symptoms into adult life [25–29]. This important finding may offer new clues to the poor treatment response in some enuretic patients with very severe symptoms. Further study of this group of adults with PNE, who in general have more pronounced and persistent symptoms than younger enuretic children, may provide further insights into the complex pathophysiology of these various subtypes, and ways to refine the management of this heterogeneous disorder.

In conclusion, PNE is as prevalent in Hong Kong Chinese schoolchildren as in western populations. The present finding suggesting that PNE will spontaneously resolve with age probably applies only to those with mild enuretic symptoms; with increasing age there is a greater proportion of enuretic children with more severe bed-wetting. Enuretic children aged >10 years, and adolescents, have significantly more daytime urinary symptoms and incontinence. The previously reported low prevalence of PNE in Hong Kong was probably due to parental indifference to the problem.

ACKNOWLEDGEMENTS

The Health Care and Promotion Fund supported this project.

CONFLICT OF INTEREST

None declared.

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