Sleep and Colic
Terminology and Definitions
The most distinctive feature of infantile colic is excessive crying. Crying, especially in the evening, is a normal behavior of infants.1 Recognizing which crying behavior should be considered excessive and requires further evaluation is a challenge for the clinician.
There is an extensive variety of definitions for excessive crying and colic. The most widely used is the one defined by Wessel at 1954, also known as ‘the rule of three:’ crying for more than 3 hours per day, for more than 3 days per week, and for longer than 3 weeks in an infant who is well-fed and is otherwise healthy.2–5
Other definitions of a ‘fussy/colicky infant’ can be grossly divided into two large groups. One group uses different time limits, while the other group relies on the different subjective estimation of the parents.5,6 When using definitions from the latter group, one has to keep in mind that there could be disconcordance between parental expectations and a ‘normal for age’ behavior. As of now, there is still no consensus on which definition is the most accurate or appropriate to be used. Despite relatively many studies in this field, more research needs to be done to elucidate this issue and lead to more commonly accepted terms and definitions.
Regarding the duration of symptoms, there are also various opinions. Reijneveld et al. demonstrated that when applying a different time frame to the same definition there is a change in the prevalence of excessive crying. When applying a time frame of ‘3 preceding weeks or longer’ in comparison with ‘during the preceding week’ the prevalence substantially declines.6 The most commonly used and the most validated is the original Wessel definition for ‘seriously fussy children’ with the requirement of ‘over 3 preceding weeks.’ For the purpose of research it is highly important to adhere to a unified definition in order for results to be comparable and for meta-analysis to be carried out. In practice, that may not be applicable, as many parents will not be willing to wait for that long. Nevertheless, acute crying might be an obvious sign of a serious illness or even a life-threatening one, and must clearly not be ignored.
Properties and ‘Natural Course’
The typical colicky crying episodes are prolonged, practically unsoothable and associated with a high-pitched cry.7,8 The episodes are sometimes accompanied by posture changes such as drawing up of the legs or clenched fists, flushing, and passing gas.8,9 Episodes are more common during evening and night hours.3,7,10,11
Besides differences in crying duration and intensity, it seems that the crying curve of the colicky infant resembles the one of the ‘average’ infant. The overall duration of crying increases gradually until it peaks at about the age of 6–8 weeks, then declines until it reaches a plateau around the age of 3–4 months.4,10,11
Prevalence
The prevalence of infantile colic in the community is estimated to be 10–40%, depending on the definition used. Since there is a large variety of definitions and different considerations to babies’ cries, it is hard to determine the exact prevalence rates.5,6
Pathogenesis
Excessive Air Load in the Gastrointestinal Tract
Based on clinical observations that infants with colic tend to pass relatively large amounts of gas,2,7 it is a common belief that excessive gas in the gastrointestinal tract causes painful abdominal distention and subsequently crying bouts. Possible sources for excessive gas may be aerophagia and colonic bacterial fermentation of malabsorbed carbohydrates.12 Though very common and accepted by clinicians and parents, this theory has never been successfully proven.3,9,12,13 Nevertheless, clinical trials with Simethicone (gas absorber) failed to prove symptomatic relieve in comparison with placebo, when treating colicky infants.14
Dysmotility
Another common belief is that the origin of infants’ crying is gut hyperperistalsis and intestinal smooth muscle spasm.9,13 This theory is supported by evidence that antispasmodic agents, such as Dicyclomine hydrochloride and Cimetropium bromide, alleviate colic symptoms.14,15 Transient dysregulation of the central nervous system was suggested as the reason for dysmotility, though no difference was found in the balance of autonomic nervous system between colicky and other infants.16
Gut Hormones
The gastrointestinal tract activity is highly regulated by different hormones. Some of them were suggested to play a role in the pathogenesis of infantile colic. Different studies found higher levels of motilin in colicky infants.17–19 Motilin is speculated to promote gastric emptying, which increases small bowel peristalsis and decreases transient time. This can also relate to the dysmotility theory. Higher levels of ghrelin were also found in colicky infants, though only in one small study.19
A recent study showed that colicky infants had higher urinary levels of 5-hydroxy indoleacetic acid, a metabolite of serotonin.20 This supported the hypothesis that some features of colic might be caused by a serotonin–melatonin counterbalancing system involving the gastrointestinal smooth muscles. Serotonin and melatonin have opposite effects on intestinal smooth muscle: serotonin causes contraction while melatonin causes relaxation.21 It was hypothesized that in some infants, the balance between circulating serotonin concentrations and intestinal smooth muscle sensitivity to serotonin might lead to painful gastrointestinal cramps in the evening when serotonin concentrations are highest.
Lack of melatonin in the first months of life may explain the lack of its needed relaxing effect.22 However, some researchers believe there is no solid scientific evidence to support this hypothesis.23
Gastroesophageal Reflux
This was suggested to be related to the pathogenesis of infantile colic, though no convincing evidence exists. Apparently, this is a distinctive common GI pathology that may coexist with infantile colic.9,13,24
Food Allergy
Food allergy was also suggested to have a role in infantile colic. Infantile colic is sometimes related to a food allergy and may represent, particularly when severe, the first clinical manifestation of atopic disease.25,26 Like gastroesophageal reflux, food allergy may also be a distinctive pathology that might mimic or co-exist with infantile colic.
Psychosocial Factors
Over the years, it was widely argued that excessive infant crying is an early manifestation of a difficult temperament, and the colicky infant is often considered to be irritable and hypersensitive.3,9 In the literature, there is only weak evidence to support this theory, as it is almost impossible to examine it in an unbiased longitudinal manner. One study attempted to explore the theory using objective physiologic tools and found no support for this theory.27 Other theories suggested that the excessive crying originates in an inadequate parent–infant interaction, though there is no clear evidence to support this theory either.3,4,9
Parental Smoking
Recent studies indicated that exposure of the child to tobacco smoking by the mother during pregnancy and after delivery, and smoking by the father, were associated with excessive crying. Moreover, it was suggested that smoking is linked to increased plasma and intestinal motilin levels, and higher-than-average intestinal motilin and ghrelin levels seem to be related to elevated risk of infantile coli.28,29
Outcome and Prognosis
Infantile colic is a transient, self-limiting condition considered to have a favorable outcome, usually resolving by the age of 4–6 months.9
On psychological grounds, several studies suggested that infants with colic are more emotional and are somewhat prone to negative moods and temper tantrums.30,31
Diagnosis
Excessive infant crying is a very common situation and the differential diagnosis is extremely broad. When excessive crying is prolonged, an organic disease is estimated to account for less than 5% of the cases.32 Nevertheless, before making the diagnosis of infantile colic, an organic cause must be ruled out.
When faced with a crying infant, the importance of a thorough history and physical examination cannot be overemphasized. Situations that may cause similar symptoms such as gastroesophageal reflux, constipation and cow milk protein allergy must be considered, as well as an acute illness or a neurologic or developmental problem. Any history suggestive of a specific pathology should be considered appropriately. Box 10-1 lists potential causes for prolonged, excessive infantile crying.
The infant’s weight percentile should be considered.
If the history and physical examination reveal no pathological condition in an infant that gains weight properly, laboratory or radiographic examinations are usually not necessary.3 A recent retrospective cohort study found that the only useful laboratory examination when evaluating a crying infant with a normal history and physical examination is urine evaluation.32 If there is a pathology suspected in the history and physical examination, evaluation should be followed accordingly.
Treatment
Once the diagnosis of infantile colic is made, the first step of management is reassuring of the parents, explaining that colic is a self-limiting condition and that the excessive crying does not reflect an underlying disease or bad parenting.9 In addition, parents should be reassured that there is no negative prognosis for infantile colic.
Dietary Interventions
Some trials examined the efficacy of elimination of potentially allergenic agents from the infant’s diet. Data regarding utilizing of hypoallergenic diets by breastfeeding mothers are inconclusive, but suggest that there may be some therapeutic benefits.33 The use of hypoallergenic formula for bottle-fed infants also appears to have a beneficial effect on colic symptoms. The benefit of using a soy-based formula is less conclusive.33,34 Further validated studies are needed to evaluate these dietary interventions.
High-fiber formulas were also tested. While the enriched formula did have a significant effect on stool characteristics, it did not influence crying duration.34,35
Two randomized-controlled trials studied the effect of lactase on infantile colic. Neither of them found a beneficial effect.33
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