Normative values of polysomnographic parameters in Chinese children and adolescents: a cross-sectional study

Objective: The objectives of this study were to characterise age-specific normal polysomnography values in healthy children and to establish reference values for paediatric sleep studies.

Methods: Healthy children and adolescents aged 3-14 years were recruited from families of hospital employees. The subjects were divided into young (three to five years old) and old (6-14 years old) groups. Each child was subjected to overnight polysomnography. The polysomnographic parameters of sleep architecture, respiratory events and oxygen saturations of the two groups were compared.

Results: Ninety-nine subjects, including 33 3-5 year olds and 66 6-14 years olds, were recruited. The old group yielded a higher per cent of N2 sleep and lower per cent of R sleep than the young group. Sleep efficiency and latency were similar between the two groups. The average of the total apnoea/hypopnoea index (AHI) was different between the two groups (1.02 ± 0.99 vs 0.51 ± 0.57, p = 0.007). The average central apnoea index (CAI) in the young group was higher than that of the old group (0.7 ± 0.82 vs 0.28 ± 0.42, p = 0.001), with 97.5 percentile of 3.8 and 1.4, respectively. The obstructive apnoea index (OAI) and obstructive apnoea hypopnoea index(OAHI) were similar in the two groups (OAI: 0.08 ± 0.12 and 0.07 ± 0.14, and OAHI: 0.18 ± 0.21 and 0.19 ± 0.26, respectively). The mean lowest SaO₂ in the young group was significantly lower than that of the old group because of central apnoea events.

Conclusions: The findings were consistent with previously published data regarding sleep architecture, oxygen saturations, and relative rarity of respiratory events in normal children. The occurrence of central apnoea varied with age. Therefore, it is suggested that different normal cut-off values be used for children in different age groups.