OBJECTIVETo explore the correlation between periodic limb movement index (PLMI) and the apnea-hypopnea index (AHI), apnea index (AI), hypopnea index (HI) and lowest oxygen saturation (LSaO₂) in sixty-four children with sleep-disordered breathing (SDB).

METHODSBetween March 2008 and May 2009, sixty-four children suspected of OSAHS underwent overnight polysomnogram monitoring in our medicine sleep center. OSAHS was diagnosed according to the general criterion. Sixty-four children were divided into two groups. Thirty children were diagnosed as OSAHS and 34 children were diagnosed as primary snoring (PS, 32 children) or upper airway resistance syndrome (UARS, 2 children). The difference of PLMI and periodic limb movement index during sleep associated with arousals (PLMI-arousal) were compared between the two groups. Besides this, the correlation between PLMI, periodic limb movement index during sleep associated with arousals and AHI, AI, HI and LSaO₂ were also analyzed in all SDB children. Furthermore, all SDB children were divided into two groups according to PLMI (< 5 events/h vs ≥ 5 events/h). AHI, AI, HI, LSaO₂ and sleep structure were compared between the two groups.

RESULTS(1) The difference of PLMI and PLMI-arousal between the children with OSAHS and children with other SDB types (PS and UARS) were not significant (z value, -1.279, -1.490; P value, 0.201, 0.136, respectively). (2) The increased sleep stage I was significant as being compared between the two groups (< 5 events/h vs ≥ 5 events/h, t = -2.16, P < 0.05). However, other sleep stages and sleep efficiency were not significantly different (P value, all > 0.05). (3) The difference of HI, AI, AHI, arousals index (ArI) and LSaO₂ were not significant between the two groups (< 5 events/h vs ≥ 5 events/h, P value, all > 0.05). (4) PLMI and PLMI-arousal were not correlated with AHI, HI, AI, AHI and LSaO₂ (Spearman rank correlation analysis).

CONCLUSIONSPLMS may be independent of SDB and PLMS had a little influence on sleep structure.