From epidemiologic studies on multiple risk factors able to affect respiratory disorders during sleep in the pediatric age, various predisposing conditions may coexist in the same subject, thus requiring a multidisciplinary approach.
Recent evidence has suggested that prematurity, maternal smoking during pregnancy, maternal age and weight gain during pregnancy, prenatal complications (such as maternal high blood pressure and gestational diabetes), and perinatal complications related to prematurity are associated with childhood SDB . Also, low socioeconomic status and race seem to influence the incidence of prenatal and perinatal complications . A recent study also indicates familial clustering of SDB (SDB caused by adenotonsillar or tonsillar hypertrophy), which is an important information for clinicians .
Our study, performed on SDB children, aimed at estimating the prevalence of the main risk factors with the analysis of the role that the atopy has in determining and/or favoring them, performing a comparison between SDB atopic children (test group) and SDB nonatopic children (control group).
In this sample of SDB children, a prevalence of atopy (55%) higher than that observed in previous literature regarding the general pediatric Caucasian population (10-15%), as reported in other studies,  was observed probably because of a selection bias that was expected because the patients were consulting a Special Service of Pediatric Allergology. This observation does not alter the validity of the results because the aim of this study is to highlight the differences between 60 SDB atopic children and 50 SDB nonatopic children.
A high prevalence of hypertrophy in the adenotonsillar lymphatic tissue in the whole sample of SDB children (54.5% adenoid hypertrophy, 38.1% tonsillar hypertrophy, and 21.5% tonsillar and adenoid hypertrophy) was also observed. This prevalence resulted significantly higher in SDB nonatopic subjects (control group) with respect to SDB atopic subjects (test group), suggesting that in our cases, the infective etiology seems to prevail, in contrast with some works  that attribute an immunogenic role in the adenoid hypertrophy,  to the allergic reaction. Recent literature shows that pediatric SDB patients with adenoid hypertrophy could be effectively treated with 4-week course of mometasone furoate, whereas allergy, obesity, and sinusitis seem not to affect the result of the treatment .
With recent studies as basis, adenotonsillar enlargement and tonsillar hypertrophy seem to mediate at least in part the epidemiologic association observed between SDB (mostly sleep apnea) and wheezing/asthma . Elevated concentrations of leukotrienes and oxidative stress markers have been detected in the exhaled breath condensate of children with asthma and probably contribute to bronchoconstriction . Moreover, SDB children with sleep apnea have increased expression of leukotrienes and leukotriene receptors in adenotonsillar tissue . Probably, viral respiratory infections may induce inflammation and oxidative stress in the asthmatic airway, enhancing not only the bronchospasm but also the biosynthesis of leukotrienes within the pharyngeal lymphoid tissues, which promote adenotonsillar enlargement and sleep apnea .
In the whole sample of SDB children, modest prevalence of obesity was observed, higher than that of the general pediatric population previously observed in the literature (35.4% in our SDB sample vs. 11%),  which is mainly prevalent (at a statistical significant level) in the control group of SDB nonatopic subjects (58% in the control group and 16.6% in the test group): contrary to what is observed in adult age,  the role of obesity in determining SDB is still debated in pediatric age .
In addition, high prevalence of nasal obstruction to rhinomanometry and alterations of the oxygen saturation to pulsoxymetry in the whole sample of SDB children (79% and 46.3%, respectively in our whole sample) were detected, which seem not related in significantly statistical terms, with the atopy. Despite the said exams being not resolutive for SDB diagnosis, they appear to be useful to point out and follow up possible complications associated with nasal obstruction, oral respiration, and allergic inflammation. In a recent study, pediatric patients with positive environmental allergic rhinitis showed SDB and sleepiness scores (on questionnaires) higher than population with normal values, suggesting that children with allergic rhinitis are at increased risk for SDB, and screening should be considered in this population .
Generally, rhinomanometric values are in agreement with symptom severity and duration (persistent and intermittent allergic rhinitis) and the degree of allergic inflammation (concentration of inflammatory cytokines)  in patients affected by allergic rhinitis. Our results suggest that the nasal obstruction, despite the atopic or nonatopic state of the subjects, appears correlated to rhinomanometry alterations.
The presence of numerous odontostomatological alterations, with various percentages in the whole sample, was observed: (a) significant reduction of the transverse diameter, equal to 75% of the cases in the whole sample; (b) a second skeletal class in 43.6% of the cases in the whole sample; (c) a cross-bite in 32.7% of the cases in the whole sample; and (d) an atypical deglutition in 91% of the cases in the whole sample.
About the palatal diameter, literature reports an increased prevalence of SDB in the population with cleft palate, with an even greater prevalence in patients with Pierre Robin syndrome .
The presence of numerous odontostomatological alterations in our sample of SDB children, both atopic or nonatopic, suggests that nasal obstruction, no matter how it is induced, is associated with altered dentofacial development at the point that orthodontic therapy has been proposed as solution for respiratory problems and oral breathing [33, 34]. With the data in literature as basis, craniofacial features considered to be risk factors for SDB include small mandible and/or high and narrow hard palate associated with a narrow nasomaxillary complex . At the same time, the degree of nasal obstruction is correlated to the severity of snoring and OSAS so that the use of rhinomanometry is suggested as screening test before polysomnigraphic recording in children with suspected OSAS .
In particular, the high percentage of children with atypical deglutition detected in our whole sample, reflects the literature data that show how this disorder is present in 50% of three-year-old children and persists till twelve years of age, in 25% of the cases [22–39]. In any case, regardless of the atopic or nonatopic state, the atypical deglutition seems to be significantly related to the oral breathing because of the high prevalence of this disorder found in our whole sample of SDB children. Recently, a research stated that a cranial lateral cephalometry is required to study cephalometric characteristics if polysomnography points out any pathology referring to SDB .
Considering the two groups of atopic and nonatopic children, we observed some little differences between the two groups, although not statistically significant.
These odontostomatological characteristics were found in slightly higher percentages in the group of SDB nonatopic subjects (control group), which coincides with the group with greater adenoid hypertrophy. The slightly higher prevalence of decrease of trasversal palatal diameter in nonatopic group seems related to the oral breathing because of adenoid hypertrophy that is prevalent in this group. Cross-bite resulted with a slightly higher prevalence in SDB atopic subjects compared with nonatopic group, although no significance was detected (35% vs. 30%), in accordance with a previous study,  suggesting a possible genetic relation.
Considering the role of atopy in SDB subjects, on the basis of our observations, atopy seems not often related in significantly statistic terms with various risk factors that trigger SDB (adenotonsillar hypertrophy, turbinate hypertrophy, odontostomatological alterations) and with particular dento-facial characteristics, except for a reduced transversal palatal diameter (p < 0.05). Children with SDB also show a high prevalence of atypical deglutition that certainly contributes to trigger malocclusions because of chronic oral respiration.
The limitation of this study concerns the selection of subjects that was made not in a pediatric general population but in a sample of children who have been evaluated in a service of pediatric allergology (in which it is obvious to find a high prevalence of atopic children).