An Italian epidemiological multicentre study of nocturnal enuresis

Authors


M.L. Chiozza Department of Pediatrics, University of Padova, Via Giustiniani 3, 35128 Padova, Italy.

Abstract

Objective

To estimate the prevalence of enuresis in schoolchildren in Italy.

Subjects and methods

The Italian Club of Nocturnal Enuresis promoted a prevalence study of nocturnal enuresis using a self-administered questionnaire in seven cities in Northern, Central and Southern Italy. The association between enuresis and potential risk factors, e.g. a family history of enuresis, stress, socio-economic status and abnormal diurnal voiding habits, was investigated. The perceived impact on the child and on the family was also evaluated. A random-cluster sampling scheme was used to obtain a sample of primary and secondary schoolchildren from each city. One primary school and one secondary school for each socio-economic level was sampled in each city, giving a total of 42 schools surveyed; 9086 children were covered by the survey. In a cluster sampling method, the variance of prevalence is divided into two components, binomial and extra-binomial variability. Both the DSM III and DSM IV definitions of enuresis were used because at present, there is no consensus on the diagnostic criteria.

Results

Completed questionnaires were received from 7012 children, an overall response rate of 77.2%. Those aged 6–14 years were analysed, restricting the sample to 6892 children. There were 250 enuretic children using the DSM III definition of enuresis and 112 using the DSM IV definition. The overall prevalence was 3.8% and showed a decreasing trend with increasing age. Bedwetting was more frequent in boys than in girls. The prevalence of enuresis was higher when the child was from a family of low socio-economic status despite the child’s age group. The logistic analysis showed that familiality, stress, birthweight, age of attaining diurnal continence, soiling and, for girls, menstruation, were statistically significant variables and thus contributed to predicting the probability of bedwetting, confirming the findings of previous studies. There was a large difference in prevalence using the two DSM definitions; a high percentage of DSM III enuretic children had more than two wet nights per week.

Conclusion

It is important that a consensus about the ‘working definitions’ of enuresis is reached to avoid bias in the recruitment step, to carry out comparable epidemiological studies and to obtain adequate therapeutic responses.

Introduction

Several epidemiological studies of enuresis report different frequencies of nocturnal enuresis in different populations, ranging from 2.3% to 25%. The frequencies reported vary depending on the geographical areas involved, the composition of the population studied and on the definition used for enuresis [1[2][3][4]–5]. Surprisingly, there are no extensive epidemiological data on the prevalence of enuresis in Italy. The Italian Club of Nocturnal Enuresis (CIEN) therefore promoted a prevalence study, using a self-administered questionnaire, in seven cities in Northern, Central and Southern Italy. The aims of the study were to ascertain the prevalence of enuresis in schoolchildren in Italy, and to investigate any association between enuresis and potential risk factors such as a family history of enuresis, stress, socio-economic status and abnormal diurnal voiding habits. The current management by different specialists involved in treatment and the perceived impact on both the child and family were also assessed.

Subjects and methods

A random cluster sampling scheme was used to obtain a sample of primary and secondary schoolchildren from each city. One primary and one secondary school for each socio-economic level was sampled in each city so that a total of 42 schools covering 9086 children was surveyed. Two different definitions of enuresis were used, the DSM III and DSM IV [6,7]; enuresis was also distinguished as primary and secondary. A child was classified as having monosymptomatic enuresis (ME) if they experienced only night wetting, and symptomatic enuresis (SE) if they had night wetting with diurnal voiding symptoms, or urinated often (≥7 times a day) and/or had an urgency to urinate and/or had damp pants. Thus four different types of enuresis were distinguished, i.e. primary ME (PME), primary SE (PSE), secondary ME (SME) and secondary SE (SSE).

Data were obtained using a self-administered questionnaire consisting of two parts, which was completed by the parents; the first part was designed to investigate risk and precipitating factors, and concerned all the children studied, and the second classified the types of enuresis, being applicable only to those considered enuretic. As the cluster sampling method chosen involved a higher variability than simple random sampling, the variance of prevalence was divided into a binomial variability arising from intra-individual variability and an extra-binomial variability, which was the component of variance from the variability among schools (clusters). Huber’s formula was used to assess the amount of extra-binomial variability in the estimates. As this variability was negligible, data were analysed using a classical logistic regression model which predicted the probability of wetting in terms of covariates.

Starting from a baseline model containing age and sex as covariates, the relevance of the following variables was then tested; social class indicator, birthweight, presence of stressful and worrying events, familiality, mother’s educational status, and age at attaining diurnal continence, soiling and menstruation. To identify which of these explanatory variables should be included in the logistic model, a likelihood ratio test was applied; a P<0.05 was considered to indicate significant differences.

Results

In all, 9086 questionnaires were distributed in the schools sampled; 7012 questionnaires were returned and only those from children aged 6–14 years were analysed, restricting the sample to 6892 children. The number of children classed as enuretic was 250 using the DSM III definition and 112 using the DSM IV definition. Thus the overall prevalence of enuresis was 3.8% (95% CI 3.4–4.3), the trend decreasing proportionately with increasing age (Table 1). Bedwetting was more frequent in boys (4.2%, 95% CI 3.6–5.0), than in girls (3.4%, 95% CI 2.8–4.1). If enuresis is defined more conservatively (DSM IV), then the overall prevalence decreased from 3.8% to 1.7% (95% CI 1.4–2.1), the prevalence in boys to 2.1% (95% CI 1.7–2.7) and that in girls to 1.3% (95% CI 0.9–1.7).

Table 1.  The number of children, prevalence and 95% CI for boys and girls according to the DSM III and DSM IV definitions of enuresis Thumbnail image of

Primary enuresis was more frequent than secondary enuresis (52.8% vs. 31.6% for DSM III, 68.8% vs. 24.1% for DSM IV). Among children with primary enuresis, SE was more common (65.1% for DSM III and 62.3% for DSM IV) than ME. This also applied to children with secondary enuresis (73.4% for DSM III and 74.1% for DSM IV). However, further analysis used the DSM III definition only, both because there were few enuretic children according to DSM IV and also so that the results could be compared with those reported by authors using the DSM III definition.

The most frequent category of bedwetting was ‘less than once a week’; however, among children with primary enuresis, 32% of boys and 33.4% of girls wet the bed 2–4 times a week and 25% of boys and 14.6% of girls 5–7 times a week. Most of the children with secondary enuresis wet the bed less than once a week, the girls in particular. All children with ME tended to urinate <7 times a day (62% and 83%, respectively). Symptomatic children with primary enuresis, the girls particularly, tended to urinate ≥7 times a day, while children with secondary enuresis, boys particularly, tended to urinate <7 times a day.

The classification of symptomatic children according to their diurnal abnormal voiding habits and sex showed that the most frequent symptom in this group was ‘urgency to urinate’ in primary (65%) and secondary (72%) enuresis for both sexes. The other two symptoms were equally frequent in primary enuresis (27%), while in secondary enuresis the ‘damp pants’ symptom seemed less usual.

The percentage of boys with secondary enuresis tended to be lower than with primary enuresis (8.7% vs. 15%), while the percentage of girls with secondary was higher than those with primary enuresis (22.9% vs. 18.2%). The prevalence of enuresis seemed to be higher in children from a family of low socio-economic class, whatever the age group. In both sexes, the prevalence of soiling decreased with age; regardless of age, the prevalence for soiling tended to be lower in girls than in boys. The number of children, prevalence rates of enuresis and estimates obtained from the logistic regression model for each explanatory variable used in the logistic model are listed in Table 2.

Table 2.  The number of children and prevalence rates for the explanatory variables of the logistic model Thumbnail image of

The odds ratio (OR) was highly significant (3.1, 95% CI 1.8–5.6) for a family history of enuresis in siblings. The comparison of PME and SME for familiality in parents gave a χ2 of 4.2 (P=0.04). The highest risk for familiality was shown by PSE (OR 12.3), while the highest risk for stress was shown by SME (OR 4.0). A positive family history of enuresis was the strongest predictor in the logistic model.

The highest risk for soiling was shown by SSE (OR 10.9); the comparison of PSE and SSE was significant for soiling (χ2=4.6, P=0.03). Moreover, there was a significant difference between primary and secondary enuresis (χ2=4.4, P=0.04) for soiling, with a stronger effect in secondary enuretic children (relative risk, RR=7.4) than in primary enuretic children (RR=3.1) whereas the remaining explanatory variables appeared to have no significant effect. The difference between ME and SE was only significant for soiling (χ2=5.8, P=0.01), which was stronger in the symptomatic (RR=6.3) cases. The highest risk for soiling was present in those with SSE. This stresses the need for a structured interview of enuretics to obtain detailed information on any abnormal diurnal voiding habits and bowel movements, and the presence of constipation and soiling. The prevalence of soiling, which decreased with age, tended to be lower in girls than in boys aged ≥10 years.

The highest risk for birthweight was shown by SSE (OR=1.7) while the comparison of SSE and SME was significant for birthweight (χ2=7.3, P=0.007), in agreement with other reports. The comparison between PSE and PME was statistically significant for each of the explanatory variables and for birthweight (χ2=5.2, P=0.03). The highest risk for stress was shown by SME (OR=4.0). The child’s experience of stressful and worrying events was an important factor in the aetiology of enuresis. The occurrence of menstruation was significant, having a protective effect (OR=0.2), suggesting that the hormonal changes at puberty may also involve the production of ADH.

When parents were asked to grade their concern about their child’s enuresis and to specify how much distress it caused them, only 24.4% reported a ‘great deal’ of concern. The distribution of enuretics according to the what the parents viewed as the cause of the problem showed that ‘behavioural problems’ were primary; 28% of parents had asked no-one for advice about their child’s problem. Overall, 52.4% of parents consulted a paediatrician only or with another specialist. The distribution according to the specialist and type of tests recommended showed that all specialists recommended urinary tests, with urine culture; specialized examinations were mainly requested by nephrologists and urologists. When medical opinions on bedwetting were assessed, the most frequent opinion was that the problem ‘will resolve spontaneously’.

Discussion

Studies on the epidemiology of enuresis often have a selection bias and sample sizes have frequently been too small to allow any definite conclusion. The present study used a random cluster sampling method, with sample sizes large enough to estimate prevalence with acceptable accuracy. A comparison between the present results and those of other epidemiological studies shows lower but more homogeneous values in the former. The overall prevalence of nocturnal enuresis using the DSM III classification was lower than that using DSM IV and showed a decreasing trend with age. Bedwetting was more frequent in boys than girls, as reported by others, and boys are more likely to present with ME; primary enuresis was more frequent than secondary. In agreement with results reported by Verhulst et al. [1], the present results show an important difference between the DSM III and DSM IV classifications, confirming that a consensus on working definitions is need to compare studies and therapeutic responses. These results confirm that the DSM III classification includes both severe and mild enuretics and can therefore be misleading.

The most frequent diurnal voiding habit was ‘urgency to urinate’ for both sexes. The number of micturitions allows ME and SE to be distinguished; moreover, 72% of children with secondary enuresis complained of the sensation of ‘urgency to urinate’. These findings stress the importance of obtaining a detailed description of diurnal voiding habits from the patient, to differentiate between the subclasses of enuresis.

The present study suggests a low level of parental and medical knowledge of the topic, particularly on the negative effects of a delayed resolution of the problem. Paediatricians must be aware that it is the child and not the parent who is of paramount importance and thus the consultation must be ‘child orientated’, because the degree of concern shown by the child emerged as an important prognostic factor in treatment of enuresis.

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