Constipation is the most common complaint in children. In a recent review the prevalence of constipation in the general population in North America was estimated between 1.9% and 27.2% (1) and 0.7% and 29.6% (median 8.9%) in children younger than 18 years (2). Moreover, habitual constipation is one of the most common diagnoses in children, constituting almost 3% of children presenting at the general pediatric clinic (3), and up to one quarter of children who attend gastroenterology specialty clinics (4).
Our personal impression at both clinics suggested that habitual (functional) constipation in children is often associated with positive family history of constipation. Indeed, recent data in adult patients reported that constipation does cluster in families (5). To our knowledge, a similar phenomenon has not been reported in the pediatric population. The present study aims to investigate whether habitual constipation in children clusters in families.
PATIENTS AND METHODS
All patients and their families were prospectively recruited to the study from the general pediatric and the gastroenterology clinics at Marshall University between August 2007 and June 2008. The inclusion criteria included children who were diagnosed with habitual constipation according to the standard Rome III criteria specifications (probands; test group) (6). The control group consisted of pediatric patients who attended both clinics for other medical reasons and who did not satisfy the Rome III criteria (6).
Exclusion criteria included children who were younger than 6 months and older than 18 years of age, children from broken families such as single parent or divorced families, and children with medical conditions that may affect gastrointestinal motility such as neuromuscular diseases, endocrine diseases, psychiatric illness, and drug abuse.
The constipation diagnosis of other members of the probands' and control families was assessed using the Rome III criteria for the siblings (6) and Rome II criteria for the adult parents (7). The study questionnaire was filled out by the parents for themselves and for their children and is described in the Appendix.
In the absence of any family member during the clinic visit (sibling or second parent), a study questionnaire with prepaid envelope was provided to the family at the same visit to complete later and return. A reminder telephone call was made to nonresponders after 1 month, or a telephone interview was performed by one of the corresponding authors (W.O., Y.E.). The corresponding authors recruited the subjects and obtained informed consent forms from all of the parents. The local institutional review board committee at Marshall University School of Medicine approved the study.
The statistical differences between the groups was assessed using the χ2 test and the Student t test. Significance was defined as P < 0.05.
A total of 140 children were interviewed, of whom 40 children were constipated (test group) and 100 children were nonconstipated (control group). The family members of 3 constipated probands and 25 of the control group did not return the questionnaire and/or did not complete a telephone interview (disconnected telephone). Accordingly, our cohort included a total of 112 children, of whom 37 (33%) were constipated probands and 75 (67%) were children with no constipation (control group). Nineteen probands were recruited from the specialty clinic and 18 probands were recruited from the general pediatric clinic. A total of 310 family members from both groups were also recruited and completed our patient study population (Table 1). No significant differences were found between test and control groups in age, sex, race (all white), or family size (P > 0.05). The constipation rate of the probands' siblings was 30% compared with 7% in control's siblings (P = 0.009, odds ratio [OR] 5.6, 95% confidence interval [CI] 4.20 [1.4–12.5]). The parents of the probands had a higher constipation rate compared with the parents of the control group (42% vs 9%, respectively; P < 0.001, OR 7.6, 95% CI 4.83 [2.7–8.7]). Thirty-eight percent of family members of probands had constipation versus 8% in the control group (P < 0.0001, OR 6.9, 95% CI 4.67 [2.8–7.8]) (Table 1).
Constipation is one of the most common diagnoses in children, approaching 3% of all clinic visits (3). The present study has demonstrated that habitual constipation in children clusters in families and that constipation is more common in the siblings and parents of the probands compared to the control group.
Family clustering of common diseases in children is not a new phenomenon and was previously described in other diseases such as gastroesophageal reflux disease (GERD) (8) and asthma (9). The discovery of familial clustering led to genetic analysis studies and identification of a new genetic link to the disease as previously reported in GERD (10–12) and asthma (13–15). For constipation, the first report of familial clustering was described in the adult population (5). In this report, the authors described that subjects who belong to a family with at least 1 member with constipation have a higher risk of having constipation (OR 2.02), and the risk almost doubled if 2 or more family members have constipation (OR 3.99). No scientific explanation was given, but the author speculated that there is a family aggregation in constipated subjects, which may be because of underlying genetic factors, intrafamilial learning, or an exposure to similar environmental factors (5).
In the present study, a similar phenomenon was found in children. We do not have any scientific explanation for our findings, but speculate that as in children with other diseases (GERD and asthma) (11–15), this clustering may be linked to a genetic etiology yet to be discovered.
Previous data suggested that the prevalence of constipation rate in the nonwhite population is higher in women compared with men and appears to rise with increasing age (1). In our study, such factors did not influence our results because no difference in age or sex was noted between the groups. Moreover, in reflection of the homogeneous distribution of West Virginia population (US Census Bureau 2006, http://quickfacts.census.gov), the vast majority of our study population (>94%) was white, thus race was not a factor in our study.
We acknowledged several possible limitations in our study including the different clinics that the patients were recruited from (general vs specialty clinics) that may lead to a skewed population of the study; and establishing the diagnosis by 2 different investigators.
Those limitations were addressed by performing a prospective study, recruiting similar numbers of constipated patients from both clinics and using standard diagnostic criteria (Rome III and II) to avoid diagnostic bias (6,7). Moreover, we controlled several confounding factors that may influence our results by reporting no differences in various demographic characteristics (age, sex, family size, and racial homogeneity) among the groups.
In conclusion, the first pediatric study of its kind demonstrated habitual constipation clusters in families. In conjunction with similar data in adults, our data suggest that genetic factors may be responsible for these findings. A multicenter prospective controlled trial is needed to substantiate our results. Furthermore, the data suggest that future studies to address the possible genetic linkage of this phenomenon are warranted.
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