We report the results of the first prospective population‐based study to examine the onset of CAP in schoolchildren. Onset of CAP in girls was common (34%) and was predicted only by previous somatic symptom reporting (headache). In contrast, onset amongst boys was less common (13%), but was predicted by psychosocial factors (conduct problems and lack of school enjoyment) in addition to previous somatic symptom reporting (daytime tiredness). Taller boys also experienced an increase in risk.
There are a number of methodological issues to be addressed. Firstly, our case definition of abdominal pain was different from those used in previous reports, the majority of which used the Apley and Naish definition,5
or the Rome II criteria for paediatric functional gastrointestinal disorders.10
We have identified schoolchildren who developed new‐onset abdominal pain that persisted/recurred 3 years subsequently. Thus, we were focusing on chronicity of symptoms rather than frequency. However, as with other potentially functional disorders (eg, fibromyalgia),11
these symptoms are likely to be part of a continuum and, therefore, any definition is to some extent an arbitrary cut‐off.
Secondly, we relied on self‐report of symptoms. Therefore, the study will detect symptoms that are, on average, milder than those seen in clinical settings. This might have led to underestimation of the strength of the risk associations. We also used a 1‐month recall period for measuring abdominal pain experience, to avoid the recall problems. So, it is possible that some of our baseline study population developed abdominal pain over the intervening period and were pain‐free again at follow‐up. If this is the case, then we will have underestimated our onset rate and, again, the true risk associations would be greater than we present here.
Thirdly, despite a high initial participation, our follow‐up rate was modest (58%). However, most children lost to follow‐up came from schools which declined to participate rather than from the individual child being absent from school. Furthermore, subsequent analysis revealed that the only individual level predictor of loss to follow‐up was age. Because age was not a predictor of CAP onset, it is unlikely that attrition will have introduced any major selection bias.
Fourthly, the sole use of the SDQ as a psychosocial tool limited the extent of psychological evaluation. However, the SDQ has been well‐validated for behavioural and emotional assessment in large community samples of this age group. Furthermore, studies have shown that self‐reported scores correlate well with parent‐ and teacher‐reported psychological scores on this instrument.12,13
We have found that the incidence proportion of CAP was 22% and was significantly higher in girls than in boys but showed little variation with age. The marked female preponderance was not attributed to menstruation, as development of CAP was considerably higher in both menstruating and non‐menstruating girls compared to boys.
Development of CAP in both genders was predicted by prior report of some somatic symptoms. It is well recognised, in both children and adults, that various somatic symptoms frequently co‐exist.7,14,15
In terms of predictors of abdominal pain, one study found that 31% of children with recurrent abdominal pain had a history of migraine.16
Similarly, studies in adults have shown that fatigue predicts abdominal pain onset.17
It has been postulated that central processing of afferent information from different regions of the body in the form of hyper‐vigilance or altered sensory modulation may play a central role in aggregation of somatic symptoms.18
The strong relationship between CAP and other somatic symptoms might also be attributed to a common aetiology shared by all these symptoms.
Other studies have found that children presenting with recurrent abdominal pain do not differ in weight and height from healthy children undergoing a routine check‐up at primary care clinics.19
This finding is partially in accordance with our results, which found that weight and BMI were not associated with the onset of CAP. However, in the current study boys of taller stature experienced an increase in the risk of CAP. There are two possible explanations for this. Firstly, that height itself is the risk factor or, secondly, that height is a marker for some other risk factor – early puberty perhaps.
What is already known on this topic
- Chronic abdominal pain is common among schoolchildren and is a major cause of school absenteeism and medical care visits.
- Although a number of cross‐sectional and case‐control studies have identified some potential risk markers, there have been no longitudinal studies of the onset of chronic abdominal pain in children.
What this study adds
- The onset of chronic abdominal pain is more common in girls than in boys.
- In girls, future abdominal pain is predicted by prior report of headaches, whereas, in boys, adverse psychosocial factors, daytime tiredness and taller stature predict pain onset.
Results of most,2,6,20
but not all,21
previous studies suggest that children with abdominal pain have more internalising emotional symptoms (anxiety and depression) than their peers. Similar studies investigating the relationship with other psychosocial problems are scarce and have been conducted in adults.22,23
In the current study, psychosocial factors were predictive of CAP development in boys but not in girls. Lack of school enjoyment, which may be indicative of psychosocial problems, was an independent risk factor for CAP in boys but, again, showed no predictive role in girls. These results are inconsistent with the findings of Ghandour et al
who found a higher prevalence of abdominal pain in adolescent girls who reported low psychosocial support.24
However, girls' psychosocial wellbeing was not directly assessed in the current study. In addition, both studies differed in terms of design and pain measurement. It is acknowledged that psychosocial dysfunction plays an important, but poorly understood, role in the pathophysiology of functional abdominal pain in adults, either directly through interaction between the central and enteric nervous systems or indirectly though influencing pain experience and medical care consultation.25,26
The potential gender‐related differences found in the current study highlight the complexity that surrounds this relationship and needs further investigation.
In conclusion, our results suggest that new‐onset CAP is common in adolescents, particularly among girls. Further, we have shown that although there are similarities, there are also differences in the predictors of CAP between boys and girls. Sex differences in pain mechanisms, perception, reporting and coping are well documented27
and these differences might be stronger in adolescence, when biological, cognitive, psychological and social changes take place in boys and girls at different rates. Our results suggest that the two genders are also different with respect to risk factors for pain development, and these factors might indicate a possible mechanism for understanding the development of CAP, and might have important implications for both primary and secondary preventive strategies.