In rodent models, compared with the young adult rats, senile rats express orexins neurons decreased 40%.[56] In human autopsy study, the effect of small amount, but it is still significant, observed in the older population reduced 10%.[57] Greater effects were observed in patients with insomnia accompanied by cognitive impairment, suggesting that a substantial loss of orexin-expressing neurons may be responsible for worsening sleep-wake instability in this context.[58,59]. The gene discussed is HCRT; the disease is insomnia.