Introduction
Sickle-cell anaemia (SCA) is the most common inherited haemoglobinopathy which affects millions of people in the Tropics especially sub-Saharan Africa [
1], and is also common among African-Americans [
2]. Nigeria accounts for the largest number of cases worldwide with a prevalence of about 20 per 1000 births [
3].
Infarction-related renal complications start from childhood [
4], and include tubulopathies like impaired ability to concentrate urine (manifesting as hyposthenuria, polyuria and enuresis) and abnormalities of urine acidification [
5‐
7].
The Diagnostic and Statistical Manual of Mental Disorders-IV (DSM-IV) criterion defines enuresis as the repeated voiding of urine into bed or clothes which may be involuntary or unintentional, the behaviour being clinically significant if manifested by either a frequency of voiding twice weekly for at least 3 consecutive months or the presence of significant distress or impairment in social, academic (occupational) or other important areas of functioning by a child five years or older and the behaviour not being due exclusively to the direct physiological effect of a substance (a diuretic) or a general medical condition (e.g., diabetes, spina bifida, seizure disorder) [
8].
Several studies in both developed and developing countries which evaluated the prevalence of enuresis among children and adolescents with SCA show that they may be at a higher risk of nocturnal enuresis than their counterparts with normal haemoglobin genotype [
9‐
14]. For instance, Akinyanju et al. [
12] reported a high prevalence value of 41.6 % in South-west Nigeria among paediatric SCA patients compared to 18.5 % in their counterparts with normal haemoglobin. Among children with SCA in Congo Brazzaville, other researchers [
9] documented a prevalence value of 50.9 and 16.4 % among their peers with normal haemoglobin genotype. However, there appears to be dearth of data on the prevalence of enuresis among affected children in the south-eastern part of Nigeria. Furthermore, abnormalities of urinalysis such as proteinuria, leucocyturia and haematuria have also been noted in other studies conducted in South-eastern part of the country [
15,
16].
The present study was thus conducted to determine the prevalence of and the risk factors for nocturnal enuresis among school-aged children with SCA seen in a tertiary health facility in Enugu, South-east Nigeria.
Subjects and methods
Study site/design/population
The study was conducted at the University of Nigeria Teaching Hospital (UNTH) - a major tertiary health facility located within Enugu metropolis, South-east Nigeria. It was a descriptive, cross-sectional study in which 70 children with SCA and their 70 age- and sex-matched controls were recruited consecutively. The Subjects were drawn from school-aged children attending the weekly Paediatric Sickle Cell Clinic of the hospital while the Controls were their classmates with normal haemoglobin genotype.
Study criteria/sampling method
After obtaining ethical approval from the Health Research and Ethics Committee of the hospital and written informed consent from the parents/caregivers, the patients were enrolled following fulfillment of the following inclusion criteria: diagnosis of SCA confirmed by haemoglobin electrophoresis; age of 5 to 11 years; stable state; clinic attendance for at least 6 months prior to the study; and primary school attendance within Enugu metropolis. Children who had a history and urine sugar level suggestive of diabetes mellitus; a history suggestive of urinary tract infection; a personal history of epilepsy and; a history of diuretic medication were excluded.
The Controls were recruited from the primary schools attended by the corresponding Subjects following the informed consent of school authorities and the parents/caregivers. The haemoglobin genotypes of the pupils selected consecutively from the class register were determined to confirm their haemoglobin AA status. On the whole, 70 Subjects with haemoglobin SS and 70 Controls with haemoglobin AA were enrolled for the study.
Data collection
A 26-item proforma consisting of open-ended questions on demographic data (such as the child’s age, parents’ educational attainment and occupation, as well as family size) and closed-ended questions on historical evaluation of enuresis based on the DSM-IV criterion (including family history of enuresis) was administered by the principal investigator (CIE) to the parents/caregivers of the enrolled Subjects and their class-mate Controls. Another 15-item proforma comprising open-ended questions on bio-data (child’s age and gender) and closed-ended questions on past medical history and evaluation for enuresis was also administered to the Subjects and Controls.
Social classification of the Subjects and the Controls was determined using the occupation and educational attainment of their parents or caregivers based on the method described by Oyedeji. [
17]. Class I represents the upper social class, Classes II and III the middle class and Classes IV and V the lower class.
Data analysis
Data entry and analysis were conducted using the Statistical Package for Social Sciences (SPSS) version 17.0 software. Descriptive statistics, including frequencies and percentages were used to summarize the socio-demographic data. Continuous variables were presented as means and standard deviation. Means were compared between continuous variables using 2 tailed Student’s t-test. The significance of the difference between the frequencies of categorical variables was ascertained using the Chi square test, or Fisher’s Exact Test as appropriate . Level of significance was at the 95 % confidence interval and p values less than 0.05. Data was subjected to multivariate analysis using logistic regression model with nocturnal enuresis as the dependent variable and the possible risk factors as the independent variables.
Conclusions
In conclusion, children with SCA have a tendency to develop nocturnal enuresis when compared to their counterparts with normal haemoglobin genotype. In addition, gender and parental history of childhood nocturnal enuresis are potential socio-demographic risk factors. It is hoped that the findings of this study will provide base-line reference data for future studies in this clime. It is recommended that school-aged children with SCA who are in steady state should be frequently evaluated for nocturnal enuresis, particularly if they are male children and have parents with history of nocturnal enuresis in childhood.
Competing interests
The authors declare that they have no competing interests.
Authors’ contributions
CIE conceived and designed the study methodology and instrument, and wrote the initial draft. SNU, ANI, and HUO revised the draft and made substantial intellectual contributions for the final draft. All the authors read and approved the final draft of the manuscript.
CIE is a Fellow of the National Medical College; and is currently a Consultant Paediatrician with the Enugu State University Teaching Hospital, Enugu
HUO is a Fellow of the National Medical College; a Professor of Paediatrics with the College of Medicine, University of Nigeria, Nsukka; and Honorary Consultant Paediatric Nephrologist, University of Nigeria Teaching Hospital, Enugu.
ANI is a Fellow of the National Medical College, the Chief Examiner of the Faculty of Paediatrics, National Medical College; Senior Lecturer with the College of Medicine, University of Nigeria, Nsukka; and Honorary Consultant Paediatric Haematologist, University of Nigeria Teaching Hospital, Enugu
SNU is a Fellow of the West African College of Physicians; a Senior Lecturer with the College of Medicine, University of Nigeria, Nsukka; and Honorary Consultant Paediatric Nephrologist, University of Nigeria Teaching Hospital, Enugu.