Bowel habits are likely to vary depending on several key factors including the age, developmental stage of the child, dietary habits, sociocultural influences, and genetic factors. Bowel habits of Asian children who have a rice-based staple diet with relatively high fiber content are likely to vary from that of Western countries, which have predominantly a wheat-based diet.
Defecation disorders such as constipation are common problems in children and adolescents worldwide, affecting 0.7% in Italy to 29.6% in Hong Kong (1). The symptom-based criteria used in diagnosis of the disorders of the lower gastrointestinal tract are based on bowel habits such as altered bowel frequency, stool consistency, volume, painful defecation, and fecal incontinence (2). Therefore, a thorough knowledge of normal bowel habits is essential for formulating these clinical diagnoses. Of the few studies that have been performed to assess the defecation patterns of normal children in the world (3–8), only 2 have been reported from Asian countries (3,4). Likewise, when formulating diagnostic criteria for defecation disorders, the bowel habits of children from Western countries have been mainly taken into account. Therefore, it is of paramount importance to understand normal bowel habits of children living in different regions of the world with diverse dietary habits and living conditions before effectively applying these criteria to diagnose defecation disorders.
Furthermore, only a handful of studies have assessed the bowel habits of children older than 10 years (5). To the best of our knowledge, no studies so far have evaluated the bowel habits of adolescents, even though constipation is a common clinical problem among them (1), affecting their quality of life (9), and also places a significant burden on the health care system (10).
The present study provides data on normal bowel habits of Sri Lankan schoolchildren ages 10 to 16 years. This provides a firm platform to evaluate defecation disorders in Asian children and adolescents in this age group.
PATIENTS AND METHODS
The present study was a cross-sectional survey. Three provinces of the country were randomly selected to represent children and adolescents ages 10 to 16 years. We selected 5 schools randomly from these provinces including 3 urban and 2 rural schools. Two schools were from the war-affected eastern province. Data collection was carried out from January to June 2007.
Details regarding the bowel habits of recruited children during the preceding 2 months were collected using a validated, self-administered questionnaire. It was in the children's native language (Sinhalese). Questions were simple and easy to understand. It contained 4 parts. The first part included demographic and geographic data about the child and the family. The second part contained questions to explore whether the child had faced family- and school-related stressful life events. The third part had questions to evaluate the bowel habits (developed from the Questionnaire on Pediatric Gastrointestinal Symptoms) (11). In the fourth part, we inquired about other symptoms and current treatments.
We distributed the information sheet in an examination setting. This ensured the privacy of each child and prevented a participant's viewing the answers of another. Research assistants were present during the time of filling out the information sheet to help children. The school administration and parents were informed before distribution of the questionnaire, and consent was obtained.
Exclusion criteria were as follows:
1. Children with disorders related to defecation [constipation, irritable bowel syndrome, nonretentive fecal incontinence as defined by Rome III criteria (2)]
2. Those who had received drugs that modify bowel habits and gut motility 2 months preceding the study
3. Those who had bowel resection or any other surgery involving the colon and rectum
4. Neurologically handicapped children
Data were analyzed using χ2 and Fisher exact test using EpiInfo (EpiInfo 6, version 6.04, Centers for Disease Control and Prevention, Atlanta, GA, and World Health Organization, Geneva, Switzerland). Mean defecation frequency between different groups was compared using unpaired t test. P < 0.05 was taken as significant. A multiple logistic regression analysis was performed on variables that were found to have significant association on univariate analysis. The study protocol was approved by the ethical review committee of the Sri Lanka College of Pediatricians.
A total of 2770 schoolchildren were recruited and 2273 (82.1%) were eligible for the present study. Of them, 1130 (49.7%) were boys. Ages ranged from 10 to 16 years with a mean age of 13.2 years and SD of 1.7 years.
Mean defecation frequency of the study sample was 6.89 (SD 2.59) per week. Defecation frequency did not significantly differ between different age groups (Fig. 1). Table 1 shows the mean defecation frequency of the study sample according to demographic, socioeconomic, and family characteristics.
Table 2 shows the distribution of bowel habits in the study sample according to sex. Following multiple logistic regression analysis, stool-withholding posture (adjusted odds ratio [OR] 1.78, 95% confidence interval [CI] 1.18–2.3, P = 0.006), large-diameter stools (adjusted OR 1.64, 95% CI 1.16–2.31, P = 0.005), and straining during defecation (adjusted OR 1.66, 95% CI 1.36–2.04, P < 0.0001) were more common in boys, whereas painful defecation (adjusted OR 0.65, 95% CI 0.48–0.87, P = 0.003) and bleeding (adjusted OR 0.32, 95% CI 0.17–0.63, P = 0.001) were more common in girls. Defecation frequency and stool consistency did not significantly differ between the sexes.
When association between socioeconomic and family factors and bowel habits were compared, children living in urban areas had a significantly higher prevalence of painful defecation (urban 14.3% vs rural 6.2%, adjusted OR 1.65, 95% CI 1.22–2.22, P = 0.001), retentive posturing (urban 6.8% vs rural 2.1%, adjusted OR 1.80, 95% CI 1.15–2.81, P = 0.01), and straining (urban 35.1% vs rural 19.9%, adjusted OR 1.25, 95% CI 1.03–1.52, P = 0.024).
Association between defecation frequency and stool consistency is shown in Figure 2. Mean defecation frequency per week was higher in those with painful defecation (7.33 [SD 2.86] vs 6.84 [SD 2.56], P = 0.006), bulky stools (7.2 [SD 2.87] vs 6.86 [SD 2.57], P = 0.045), and blood-stained stools (7.8 [SD 3.82] vs 6.87 [SD 2.56], P = 0.01), whereas it did not differ in those with stool withholding posture (7.12 [SD 3.1] vs 6.88 [SD 2.57], P = 0.35), straining (6.85 [SD 2.66] vs 6.9 [SD 2.52], P = 0.6), and abdominal pain (6.82 [SD 2.84] vs 6.92 [SD 2.35], P = 0.34).
The association between exposure to school- and family-related stressful life events and bowel habits is shown in Table 3. Following multiple logistic regression analysis, bowel frequency <3/week (adjusted OR 2.69, 95% CI 1.76–4.11, P < 0.0001), large-diameter stools (adjusted OR 2.76, 95% CI 1.82–4.2, P < 0.0001), painful defecation (adjusted OR 1.58, 95% CI 1.15–2.19, P = 0.005), and withholding posture (adjusted OR 2.07, 95% CI 1.3–3.31, P = 0.002) were independently associated with exposure to stressful life events.
The present study evaluated bowel habits of normal children from 10 to 16 years. We found that more than three-quarters of Sri Lankan children and adolescents open their bowels daily, and approximately 88% produce stools normal in consistency. Children exposed to stressful life events have a higher prevalence of large-diameter stools, withholding posture, straining, and pain during defecation. Children living in the war-affected areas of the country had a lower defecation frequency.
Most of the children in our study sample (77.1%) opened bowels daily, with a mean bowel frequency of 6.89/week. Mean defecation frequency did not vary significantly in different age groups. Even though they were much younger age group, 4-year-olds in Myanmar had daily bowel openings in 74.4%, with a mean defecation frequency of 6.53/week (4). Myanmar and Sri Lanka have similar rice-based diets. Several previous studies have reported a relatively stable mean defecation frequency in children older than 2 years (5), which may explain the agreement between the 2 samples, despite the difference in age. Mean defecation frequencies in our children 10 to 12 years of age (6.44–7.1/week; Fig. 1) were higher than that reported by Corazziari et al (5) among Italian children of the same age (5.92–6.33/week). A few studies have so far reported bowel characteristics in children other than defecation frequency and consistency (5,12), but none in children older than 10 years. Similar to infrequent defecation, prevalence of large-diameter stools, withholding posture, and fecal incontinence are also higher in children in Western countries, such as the United States, than in our study sample (12). The main diet of Sri Lankan children is rice based, which has a relatively high content of fiber. Fiber is known to increase stool volume, colonic transit, and defecation frequency (13). High fiber content in the Sri Lankan diet may have contributed to the difference in bowel habits in our study sample. However, some previous studies have reported variation in bowel frequency and colonic transit between different ethnic groups, which were not explicable in terms of dietary habits and fiber intake (7), whereas others failed to find such difference (12).
Children who were the only child and those living in a family of 4 or more children had lower defecation frequencies compared with families with 2 to 3 children. The exact reason for lower defecation frequency is far from clear in those who were the only child in the family. A previous study in Italian children reported overcrowding as a predictor for lower defecation frequency and constipation even though they failed to demonstrate an association with the family size (5). Free access to the toilet is limited in a crowded house with a large number of children. The competition between family members to use the toilet, especially in the morning before going to school or work, results in postponement of evacuation, causing stool retention and constipation. Furthermore, parents' attention to the bowel habits of individual children is limited in such a situation.
Genetic factors influence gastrointestinal function and bowel habits. In their study, Corazziari et al (5) found significantly lower defecation frequency in those with a history of constipation in mother, father, and siblings. In contrast to this, family history of constipation had no such relation to defecation frequency in our study. Corazziari et al (5) obtained information from parents, whereas our questionnaire was filled out by the children themselves. Insufficient knowledge of children's bowel habits and constipation in their parents and siblings would have contributed to the lack of such association in our study.
In our study, painful defecation, withholding posture, and straining were significantly higher in schoolchildren living in urban areas as compared with rural areas. Children living in urban areas are likely to consume more junk food and less fiber and to have a more sedentary lifestyle, and this may have contributed to our results. Furthermore, we also expected to find lower defecation frequency in these areas, but in contrast to our hypothesis, we failed to demonstrate such a significant difference. Similar to our results, Walker and Walker (7) did not find a difference in defecation frequency in South African black children living in urban and rural areas.
We did not find a significant sex difference in defecation frequency and consistency, which is in agreement with several previous studies (4,5). In our study, large-diameter stools, withholding posture, and straining were more common in boys, whereas painful defecation and bleeding were more frequent in girls. Similar to our results, large-diameter stools were more commonly seen in American boys, but straining was more frequent in girls (12).
It is believed that hard stools make defecation more difficult and result in decreased defecation frequency. Corazziari et al (5) reported a positive relation between decreased defecation frequency and presence of hard stools, painful defecation, rectal bleeding, and encopresis in Italian children. In contrast to this, in the present study, children with hard stools, painful defecation, bleeding, and bulky stools had passed stools at more frequent intervals than those with normal bowel habits. The exact reason for this finding is unclear. Once-daily bowel evacuation is encouraged in Sri Lankan children from the beginning of their toilet training. Due to this practice, even when it is difficult to defecate due to hard stools, some children are likely to strain and try to empty the bowel. This may have resulted in passage of small, pellet-like hard stools several times per day, increasing defecation frequency in the children.
Our study has reported significantly lower defecation frequency and higher prevalence of painful defecation, large-volume stools, and retentive posturing in those who were exposed to stressful life events. In a previous study, we found a significant negative correlation between defecation frequency and number of stressful events exposed; in both constipated and nonconstipated children (14). Some children fail to cope with stressful life events, which results in stress internalization, anxiety, and distress. Previous studies have demonstrated slow colonic transit in adult patients with psychological symptoms including anxiety and depression (15,16). Psychological distress is associated with pelvic floor tension and increased extrinsic nerve supply and rectal-mucosal blood flow to the gut (17,18). Furthermore, in patients with constipation, emotional stress probably acts via the enteric nervous system to inhibit colonic motility, thus prolonging colonic transit (19). Alteration in bowel habits in our children is likely to result from the link between central brain activity, enteric nervous systems, and anorectal function. Additional studies are required to assess the exact relation between them.
We found a significantly lower defecation frequency in those from middle and lower social classes compared with the upper class (according to father's occupational status). Previous studies in adults have demonstrated a significantly higher prevalence of upper and lower gastrointestinal symptoms (including symptoms of constipation) in those with lower socioeconomic status (20,21). Lower socioeconomic status leads to exclusion from economic, social, and cultural spheres and lack of choice and control over the material environment. Those from the middle class have high expectations. The social deprivation and psychological distress lead to depression and anxiety (22) and, similar to emotional stress, result in alterations of bowel habits via the brain–gut axis. Furthermore, variations in dietary habits and lifestyle between different social classes are also likely to contribute to the difference in defecation frequency between them.
In our study, children living in the war-affected eastern province had a significantly lower defecation frequency. During the period of data collection, the government forces were carrying out war operations to liberate this province from the separatist terrorist group. Living in a war-affected area is an independent stressful event different from common family- and school-related stressful life events. The effect of war on bowel habits has been poorly studied. The constant anxiety, emotional stress, and feeling of insecurity related to war and terrorist activities probably have affected the bowel habits of children in the war-torn areas. Stress related to war probably results in modulation of the brain–gut axis, affecting gut motility and bowel habits in our children. We previously reported a higher prevalence of constipation in this area (14). Pizarro et al (23) reported a higher prevalence of gastrointestinal diseases in soldiers after combat exposure. Furthermore, incidence of gastrointestinal symptoms such as recurrent abdominal pain was reported to be higher after the September 11, 2001 terrorist attacks on the United States (24).
The present study provides data on the normal bowel habits of Sri Lankan schoolchildren ages 10 to 16 years. The bowel habits and behaviors related to defecation of Sri Lankan children differ from those of Western children, and may be due to dietary, genetic, and environmental variations. These variations must be taken into consideration when diagnosing and managing defecation disorders in Sri Lankan children. In this context, our results will provide a platform to evaluate defecation disorders in Asian children and adolescents in this age group.
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