Background: Childhood obstructive sleep apnoea (OSA) is increasingly being recognised. Its effects on blood pressure (BP) elevation and hypertension are still controversial. Objective: To evaluate the association between OSA and ambulatory BP in children. Methods: Children aged 6-13 years from randomly selected schools were invited to undergo overnight sleep study and ambulatory BP monitoring after completing a validated OSA questionnaire. OSA was diagnosed if the obstructive apnoea-hypopnoea index (AHI) was .1, and normal controls had AHI ,1 and snoring ,3 nights per week. Children with OSA were subdivided into a mild group (AHI 1-5) and moderate to severe group (AHI .5). Results: 306 subjects had valid sleep and daytime BP data. Children with OSA had significantly higher BP than normal healthy children during both sleep and wakefulness. BP levels increased with the severity of OSA, and children with moderate to severe disease (AHI .5) were at significantly higher risk for nocturnal systolic (OR 3.9 (95% CI 1.4 to 10.5)) and diastolic (OR 3.3 (95% CI 1.4 to 8.1)) hypertension. Multiple linear regression revealed a significant association between oxygen desaturation index and AHI with daytime and nocturnal BP, respectively, independent of obesity. Conclusions: OSA was associated with elevated daytime and nocturnal BP, and is an independent predictor of nocturnal hypertension. This has important clinical implications as childhood elevated BP predicts future cardiovascular risks. Future studies should examine the effect of therapy for OSA on changes in BP.In adults, obstructive sleep apnoea (OSA) is an independent risk factor for hypertension and is involved in the initiation and progression of other cardiovascular diseases.1-3 However, corresponding data for the paediatric population are scarce, and the few published studies have provided conflicting results. [4][5][6][7][8][9] Marcus and colleagues 4 suggested that children with OSA had higher daytime and nocturnal diastolic blood pressure (BP) compared with primary snorers, whereas Amin and colleagues 5 found lower diastolic BP among children with OSA. Guilleminault and colleagues 6 demonstrated that a subgroup of children with OSA were hypotensive rather than hypertensive. Kohyama and colleagues 7 found a positive correlation between both nocturnal systolic and diastolic BP with severity of OSA and, similarly, Enright and colleagues 8 found respiratory disturbance index to be significantly associated with systolic and diastolic BP. A recent study, however, failed to confirm such a positive association.9 These inconsistent findings in BP measurements might have been related to the small sample sizes and lack of normal healthy subjects for comparison. A recent meta-analysis concluded that there was inadequate evidence for an increased risk of elevated BP in children with OSA. The authors also found marked heterogeneity among published series and emphasised the need for further studies to clarify this important issue.

Objective To determine the prevalence and risk factors of obstructive sleep apnoea syndrome (OSAS) in Chinese children using a two-phase community-based study design. Methods Children from 13 primary schools were randomly recruited. A validated OSAS screening questionnaire was completed by their parents. Children at high risk of OSAS and a randomly chosen low-risk group were invited to undergo overnight polysomnographic study and clinical examination. The the sex-specific prevalence rate was measured using different cutoffs (obstructive apnoea hypopnoea index $1, $1.5, $3 and $5 and obstructive apnoea index $5) and risk factors associated with OSAS were evaluated with logistic regression. Results 6447 completed questionnaires were returned (out of 9172 questionnaires; 70.3%). 586 children (9.1%; 405 boys and 181 girls) children belonged to the highrisk group. A total of 619 (410 and 209 from the high and low-risk group, respectively) subjects underwent overnight polysomnagraphy. Depending on the cutoffs, the prevalence rate of childhood OSAS varied from 4.8% to 40.3%. Using the International Criteria of Sleep Disorders version II, the OSAS prevalence for boys and girls was 5.8% and 3.8%, respectively. Male gender, body mass index z-score and increased adenoid and tonsil size were independently associated with OSAS. Conclusions The prevalence rate of OSAS in children was contingent on the cutoff used. The inclusion of symptoms as a part of the diagnostic criteria greatly reduced the prevalence. A further prospective and outcome study is needed to define a clinically significant diagnostic cutoff for childhood OSAS.Childhood obstructive sleep apnoea syndrome (OSAS) is a sleep-related breathing disorder characterised by intermittent upper airway obstruction that disrupts normal ventilation and sleep patterns. Increasing evidence suggests that childhood OSAS is an important public health problem. Children with OSAS have higher respiratory disease-related morbidity and healthcare utilisation starting from the first year of life until the date of diagnosis.2 If left untreated, the condition is associated with cardiovascular and neurocognitive consequences with significant long-term clinical implications. The reported prevalence of childhood OSAS varied from 0.1% to 13%. 9 The wide range of prevalence rate was mostly related to methodological issues, including lack of polysomnographic confirmation, different sampling strategies, small sample size and the different diagnostic threshold used for defining childhood OSAS. In addition, there is a suggestion of ethnic difference in the prevalence of OSAS, with African-American children having a higher prevalence compared with white children in the USA.10 11 In a recent review, the authors commented that additional work in childhood OSAS epidemiology is needed and standardisation of selection and diagnostic criteria across studies would be helpful in future crossethnic comparisons. 9 The ascertainment of a reliable and accurate prevalence of childhood OSAS will allow ...

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