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Chest. 2004 Nov;126(5):1467-72.

Is a 2-night polysomnographic study necessary in childhood sleep-related disordered breathing?

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Department of Psychiatry, Shatin Hospital, Shatin, The Chinese University of Hong Kong, Hong Kong.



There are limited data on the night-to-night variability of childhood sleep-related disordered breathing (SDB). We aim to assess for the presence of first-night effect (FNE) and to examine whether a single-night sleep study is adequate in the assessment of childhood SDB.


In a case-control study investigating whether obesity is a risk factor for childhood SDB, the night-to-night variability of sleep and respiratory variables were studied.


Forty-six obese children from a pediatric obesity clinic and 44 age- and sex-matched normal weight control subjects from local schools.


All subjects underwent two consecutive overnight polysomnographic studies. An obstructive apnea index (OAI) >/= 1/h was considered diagnostic of SDB.


The mean age of the children was 11.21 years (SD 2.21). Forty-four obese children and 43 control subjects completed the 2-night study. Based on the criterion of the worst OAI over the 2 nights, 13 subjects were found to have SDB, 12 subjects were primary snorers, and 62 were normal subjects. In all subjects, the sleep efficiency improved and sleep-onset latency was reduced on the second night. While there was a rebound of rapid eye movement sleep with the associated worsening of respiratory indexes (mainly accounted for by an increase in central apneas and hypopneas) evident in normal subjects, there was a significant improvement of respiratory disturbances in the SDB group on the second night. The first-night polysomnography would have correctly identified 84.6% of cases as defined by the criteria of the worst OAI over the 2 nights. All cases missed by the first-night study had only borderline OAI.


The phenomenon of FNE in children was well demonstrated in our study. We proposed that a single-night sleep study is adequate and more cost-effective in assessing for childhood SDB.

[Indexed for MEDLINE]

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