Presentations of primary hypersomnia in Chinese children

To retrospectively describe childhood presentations of primary hypersomnia with an emphasis on narcolepsy-cataplexy in a Chinese population.

A total of 417 children (< 18 years old) successively presenting with complaints of hypersomnia without anatomic cause or sleep apnea risk were evaluated using the Stanford Sleep Inventory, human leukocyte antigen (HLA) DQB1*0602 typing, and MSLT recordings. CSF hypocretin-1 was measured in 47 cases to document hypocretin deficiency. A subgroup ("narcolepsy/hypocretin deficiency") with likely hypocretin deficiency (low hypocretin-1 or HLA positive with clear-cut cataplexy) was further examined for presentations prior to, around, or after puberty.

Narcolepsy with (n = 361) or without (n = 17) cataplexy presented at an earlier age and with increased male predominance when compared to idiopathic hypersomnia (n = 39, P < 0.01). Nearly 70% of those with narcolepsy/hypocretin deficiency (n = 271) had disease onset before age 10 y, and 15% had onset before age 6, an unusually young age distribution. Onset was prior to puberty in 78% of cases. Clinical features were similar in presentations across puberty groups except for sleep paralysis, which increased in frequency with age/puberty. Mean sleep latency (MSL) decreased and the number of sleep onset REM periods (SOREMPs) increased with age/puberty, but MSLT diagnosis criteria (MSL ≤ 8 min, ≥ 2 SOREMPs) were similarly positive across groups. Familial clustering was present in only 1.7% of probands.

In children presenting with a complaint of primary hypersomnia to a sleep clinic in China, 86% (361/417) meet criteria for narcolepsy with cataplexy. Puberty did not affect positivity on the MSLT as a diagnostic feature. Sleep paralysis was the only symptom that increased with increasing age. In addition, narcolepsy with cataplexy in our clinic population appeared to begin at a younger age than usually reported in other studies.