Blue Light Delays Sleep
As recently as the 1980s, researchers assumed the human sleep-wake cycle was not sensitive to light, recalls Charles Czeisler, chief of the sleep and circadian disorders division at Brigham and Women’s Hospital.
“In reality, it is the most important synchronizer of human circadian rhythms.” In the ’80s, Czeisler discovered that specialized ganglion cells in the retina are finely tuned to tell the brain to cut melatonin production when they are hit by a short wavelength (around 480 nanometers) — precisely that of morning light. Unfortunately, most phone and tablet screens and LEDs emit a similar bluish wavelength, making them exponentially more potent than older yellowish-orange incandescent bulbs.
One 2014 study found sleep lab subjects who read from an iPad before bed saw nighttime melatonin levels plummet
55 percent after five days (paper book readers saw no reduction). They also took longer
to fall asleep, had less REM-stage sleep and were groggy in the morning.
Narcolepsy May Be an Autoimmune Disease
A July 2015 study in Science Translational Medicine lends new support to the hypothesis. Since the late 1990s, scientists have known narcoleptics lack neurons that produce neuropeptides called hypocretins, which regulate wakefulness.
Many also carry a gene variant associated with producing an overzealous immune response when exposed to pathogens. During the 2009 H1N1 flu epidemic, millions of Europeans were given the vaccine Pandemrix; 1,300 developed narcolepsy. The drugmaker discontinued it. Relying on tests that used blood from Pandemrix recipients, the study authors showed it triggered antibodies that not only attack the virus but also bind to hypocretin receptors, potentially killing them.
“There is an immunological case of mistaken identity,” explains study author Lawrence Steinman of Stanford’s Beckman Center for Molecular Medicine. Previous research suggests exposure to a virus may elicit a similar reaction in genetically predisposed people, leading to narcolepsy. One highly publicized 2013 study linking autoimmune disease and narcolepsy was retracted when its authors could not replicate it. But this new study adds to a growing body of data that further confirm the theory, says Steinman.
Dreams Can Come Alive
When most people enter the dream-filled REM stage of sleep, their brain mercifully paralyzes most muscles. But for those with REM sleep behavior disorder, abnormal activity in the brain stem prompts the system to break down.
First identified in the 1980s by Minnesota sleep researchers, the disorder prompts patients to act out their dreams, sometimes severely injuring themselves or others. According to a 2015 review in JAMA Neurology, 0.5 percent of people have the disorder. Interestingly, half develop Parkinson’s disease or related neurodegenerative disorders within a decade of onset, and 80 to 90 percent go on to develop it in their lifetime. “It is the canary in the coal mine,” says review author Michael Howell of the University of Minnesota. He hopes to follow those with the disorder to better understand Parkinson’s.