Sleepiness in MMD1 Not Due to Low Orexin

People with type 1 myotonic dystrophy (MMD1) (linked to chromosome 19) appear to spend more time than others in REM (rapid eye movement) sleep, the phase of sleep in which dreaming occurs. They're also more likely to fall asleep during the day, according to evidence from sleepiness questionnaires and clinical tests.

However, MDA grantee Emma Ciafaloni, a neurologist at the University of Rochester (N.Y.), and colleagues, whose results were presented at a meeting of the International Myotonic Dystrophy Consortium in Quebec in October 2005, found no difference in levels of the protein orexin in the spinal fluid of people with MMD1 and that of people without the disease. Ciafaloni had hypothesized that this protein, which regulates sleep and wakefulness, might be deficient in MMD.

People with MMD2 (linked to chromosome 3), whose sleepiness was assessed only by questionnaire, didn't differ from a control group.