Pediatric Respirology and Critical Care Medicine

: 2017  |  Volume : 1  |  Issue : 3  |  Page : 59--62

Prevalence and risk factors for symptoms of attention deficit and hyperactivity in primary snoring children

Mei-Ching Chan1, Sharon Wan-Wah Cherk1, Ka-Li Kwok1, Shuk-Yu Leung1, Jonathan Pak-Heng Ng1, Rachel Shui-Ping Lee1, Tracy Man-Kiu Ma2,  
1 Department of Paediatrics, Kwong Wah Hospital, Hong Kong, China
2 Department of Clinical Psychology, Kwong Wah Hospital, Hong Kong SAR, China

Correspondence Address:
Mei-Ching Chan
Department of Paediatrics, Kwong Wah Hospital, Hong Kong SAR


Aim: Primary snoring was reported to affect 7.2% of school children in Hong Kong, and emerging evidence suggested that neurobehavioural symptoms were more frequently found among this group of children. The current study investigated the prevalence of symptoms of attention deficit hyperactivity disorder (ADHD) i.e., attention deficit, hyperactivity and impulsivity (ADHI), in Chinese children with primary snoring. Materials and Methods: Polysomnography results and relevant clinical notes for all Chinese children aged 4–18-year performed from January 2009 to December 2010 in our sleep laboratory were retrospectively reviewed. Data of the Chinese version of modified Epworth Sleepiness Scale and C-domain of Paediatric Sleep Questionnaire were analysed. Results: In primary snorers, the presence of excessive daytime sleepiness (EDS) and higher apnoea–hypopnea index (AHI) were risk factors for symptoms of AD with adjusted odds ratio of 3.2 (95% confidence interval [CI] = 1.2–8.1) and 4.7 (95% CI = 1.1–20.7), respectively. Primary snorer with AD symptoms had higher AHI, 0.32 ± 0.31 compared those without symptoms, 0.21 ± 0.29, P = 0.038. EDS was an independent risk factor for ADHI with odds ratio of 4.7 (95% CI = 1.1–20.0). Conclusion: Early screening for symptoms of ADHD should be performed in children with primary snoring.

How to cite this article:
Chan MC, Cherk SW, Kwok KL, Leung SY, Ng JP, Lee RS, Ma TM. Prevalence and risk factors for symptoms of attention deficit and hyperactivity in primary snoring children.Pediatr Respirol Crit Care Med 2017;1:59-62

How to cite this URL:
Chan MC, Cherk SW, Kwok KL, Leung SY, Ng JP, Lee RS, Ma TM. Prevalence and risk factors for symptoms of attention deficit and hyperactivity in primary snoring children. Pediatr Respirol Crit Care Med [serial online] 2017 [cited 2022 Oct 3 ];1:59-62
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Full Text


The prevalence of habitual snoring ranged from 3% to 35% in children aged under 13 years and 8%–12% in children aged 2–8 years.[1] In Hong Kong, it was reported that the prevalence of habitual snoring was 7.2%–10.9% in children aged 5–14 years.[2],[3] Snoring is often the presenting symptom of sleep disordered breathing, a spectrum that ranges from primary snoring (PS) to obstructive sleep apnoea syndrome (OSAS).[4] PS, defined as children who snore but do not demonstrate apnoea on polysomnography (PSG) i.e., apnoea–hypopnea index (AHI) ≤1/h, was found to occur in 6.1% of primary school children.[5] PS is considered as a benign condition and treatment is usually not considered necessary. However, there is increasing evidence that neurocognitive and behavioural symptoms such as hyperactivity, attention deficit (AD), poor school performance, excessive daytime sleepiness (EDS) and executive function difficulties were more frequently found in children with PS compared to those who never snored.[6],[7] In the present study, a retrospective analysis was undertaken to estimate the prevalence of symptoms of AD hyperactivity disorder (ADHD) i.e., AD, hyperactivity and impulsivity (ADHI) in a cohort of Chinese children aged 4- to 18-year of age referred to the sleep laboratory for suspected OSAS.

 Materials and Methods

PSG and relevant clinical notes of eligible Chinese children aged 4–18-year were reviewed. The PSG was conducted from January 2009 to December 2010. It was approved by the Clinical Research Ethics Committee, Kowloon West Cluster, Hospital Authority, Hong Kong.

Data of the Chinese version of modified Epworth Sleepiness Scale (mESS)[8] and the C-domain of Paediatric Sleep Questionnaire (PSQ)[9] were also reviewed. mESS is a validated tool to assess daytime sleepiness in Chinese children. It includes 8 questions with a 4-point rating scale for each of the questions (0 = never; 1 = slight chance; 2 = moderate chance and 3 = high chance). A score of more than 8 points is considered to be significant. PSQ is a questionnaire developed by Chervin et al.[10] in 1999 to evaluate children aged 2–18 years for sleep-related breathing disorder and symptoms. There are 3 domains: (a) Breathing symptoms; (b) EDS symptoms and (c) inattention/hyperactive behaviour. In domain C, items for inattention and hyperactivity are taken from DSM-V category A symptoms for attention-deficit hyperactivity disorder.[11] The answer to each question is either 'Yes' or 'No' or 'Don't know'.

In the current study, the validated Chinese version of PSQ was used[9] and the C-domain, which contained 18 ADHI-related questions, was the focus. Questions C1–C9 were about symptoms of AD. The presence of more than 6 symptoms was suggestive of AD. Questions C10-18 were related to symptoms of HI. The presence of more than 6 symptoms was suggestive of problems with HI. The PSQ questionnaire only enquired for the presence of symptoms suggestive of ADHI, without the details required in DSM-V criteria for the diagnosis of ADHD.


PSG studies were performed overnight in a single room in all individuals with the Siesta Profusion-3 system (Compumedics, Victoria, Australia). No sedative was used. Continuous video recording using an infrared video camera was performed after obtaining written consent from the parents. The following parameters were recorded during the study; four electroencephalographic channels (C3-A2, C4-A1, O1-A2 and O2-A1), right and left electrooculogram tracings, submental electromyogram, tibial electromyogram, electrocardiogram, snoring sound, nasal airflow, oral airflow, chest and abdominal wall motion, body position, oxygen saturation and end-tidal carbon dioxide monitor (Novametrix 7100 CO2SMO Capnograph/Pulse Oximeter, USA). All data were stored for off-line analysis. Sleep architecture was scored manually according to the prevailing American Academy of Sleep Medicine Paediatric scoring criteria. Obstructive apnoea was defined as the cessation of airflow despite breathing effort for more than two respiratory cycles. Obstructive hypopnea was defined as the decrease of airflow by >50% but <80% of baseline associated with a desaturation of ≥3% or arousal despite breathing effort. The obstructive AHI was the summation of the number of obstructive apnoea and obstructive hypopnea and mixed apnoea per hour of sleep. In the current study, we used AHI >1.0/h to define OSA.[12]

Exclusion criteria

Children with the following conditions were excluded: Syndromal disorders such as Down's syndrome, neuromuscular disorders, craniofacial anomalies, previous tonsillectomy or adenoidectomy or have ever received or was on long-term psychostimulants during the time of PSG (e.g., methylphenidate, atomoxetine, modafinil, adrafinil, armodafinil, amphetamine), alpha 2-agonist (e.g., clonidine) or antidepressants.

Statistical analysis

Univariate logistic regression models for AD and HI were developed to explore the relative contributions of the various risk factors. The potential risk factors used for both models were gender, age, EDS, sleep duration, body mass index (BMI) z score, presence of habitual snoring, arousal index and AHI.[13] Any potential risk factors with P < 0.2 in the univariate logistic regression model were entered into the multivariate logistic regression. The significant level for all statistical analysis was P < 0.05. All analyses were conducted using IBM SPSS Statistics for Windows, Version 22.0. (IBM Corp. in Armonk, NY, USA).


During the study, a total of 104 eligible primary snorers were identified. There were 59 boys (57%). The mean (standard deviation [SD]) age was 11.5 (3.4) years. The mean (SD) BMI-z was 0.85 (1.1). The mean (SD) AHI was 0.3 (0.3)/h. The mean (SD) arousal index was 7.91 (6.8)/h. The mean (SD) sleep duration was 8.4 (1.4) h [Table 1].{Table 1}

There was a male predominance (M:F 57% vs. 43%) among our PS individuals. Twenty-seven (26%) of the individuals had EDS (mESS score >8). Twenty-three (22%) and seven (8%) of the subjects had significant symptoms of AD and HI respectively with male predominance i.e., 3.6:1 and 6:1 respectively. Ten (10%) of the individuals had combined symptoms of AD and HI.

In the current group of primary snorers, those with EDS and higher AHI were more likely to have symptoms of AD. The adjusted odds ratios (95% confidence interval [CI]) of having AD symptoms in those with EDS and higher AHI were 3.2 (1.2–8.1) and 4.7 (1.1–20.7), respectively. The AHI of primary snorers with AD symptoms was significantly higher than those without AD symptoms, 0.32 ± 0.31 vs. 0.21 ± 0.29, P = 0.038. Results from multivariate logistic regression showed that EDS and AHI were significant risk factors for AD [Table 2]. There was no significant risk factor identified for HI [Table 3]. EDS was a significant risk factor identified for symptoms of ADHI with odds ratio of 4.7 (95% CI = 1.1-20.0), P = 0.036 [Table 4].{Table 2}{Table 3}{Table 4}


The worldwide prevalence of ADHD was 5.29%.[14] In China, Taiwan and the United States, the prevalence were 5.9%,[15],[16] 9.9%[17] and 9.5%[18] respectively. The prevalence of ADHD was higher in boys, with male to female ratio between 3:1[17],[19] and 9:1[11] worldwide and in the United States, male to female ratio in AD, HI and ADHI were 1.3:1, 1.8:1 and 2.8:1 respectively.[20] In Hong Kong, the prevalence of ADHD in Chinese schoolboys was estimated to be 8.9% according to the DSM III-R criteria.[21]

Our findings corroborated previous studies that neurobehavioural symptoms were more frequently found in children with PS compared to those who never snored.[5],[22] In a 4-year prospective cohort study, Chervin et al. also found that habitual snoring or loud snoring were strong risk factors for future emergence or exacerbation of hyperactive behaviour.[23] However, no risk factors were identified for symptoms of HI in the current study. This could be related to the small sample size. The mechanism for the link between PS and neurobehavioural symptoms remains unclear. The postulated mechanisms were sleep fragmentation and sleep disruption in children.[5] Sleep fragmentation resulting in EDS was suggested to be contributory to neurobehavioural impairment.[22]

In the current study, within the normal AHI range, a higher AHI index was associated with higher risk of having AD symptoms, supporting the suggestion that children with AHI within the normal range may also be clinically abnormal as suggested by Guilleminault and Lee.[24]

The current study showed that 9.6% of children with PS had symptoms of ADHI. EDS was an additional risk factor for ADHI symptoms in primary snorer. Even in primary snorer, those with higher AHI were more likely to have AD symptoms.


Therefore, children with PS should be screened for symptoms of ADHI to be followed by objective measures on neurocognitive and behavioural function assessment so as to better quantify the impact of PS on the brain. Further studies to investigate the underlying mechanism between PS and the development of neurobehavioural disorders are warranted.


In our study, children who were screened to have significant ADHI symptoms did not have further evaluation according to the DSM-V criteria to confirm the diagnosis. Other limitations included the absence of information about respiratory event-related arousal and flow limitation which were part of sleep disordered breathing that may account for the neuro-behaviour disorders as well as the absence of information about other risk factors such as prematurity,[25] prenatal exposure to tobacco, alcohol and illicit drugs[26],[27] and low paternal education.[27]

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.


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