Sleep Disorders Traced to Genesby Randy Dotinga
Researchers at two American universities suspect that night owls inherit their sleep patterns, and they're launching a study that could lead to new gene therapy for everyone from insomniacs to early birds who can't help but hit the sack before prime time.
It may be years, even decades, before gene-based drugs compete with the traditional insomnia remedies of sleeping pills, warm milk or hot toddies.
Researchers only began to seriously explore the genetics of sleep in the mid-1990s, and they're far from determining which genes are in charge of the body clock. Even so, there appears to be a general consensus that many of us don't voluntarily choose to be short sleepers or long sleepers, morning people or night people.
"For some time now, doctors who see people with sleep disorders have been documenting a familial relationship in these things. That's commonly the first way that people start thinking about a particular disease as being genetic, by seeing it cluster in families," said Dr. Walt Klimecki, a geneticist at the University of Arizona who is working with sleep researchers at the University of California at San Diego.
Indeed, researchers have discovered that some people seem to inherit a pesky early-to-sleep/early-to-rise syndrome. A notorious sleep disease -- the rare fatal familial insomnia, which robs people of sleep until they die from lack of it -- also runs in families.
Researchers at UCSD are recruiting Southern California night owls to undergo monitoring and genetic testing to see if their condition is inherited too. The participants have a condition called delayed sleep-phase syndrome and typically prefer to go to bed in the early hours of the morning and wake up after 9 or 10 a.m., when many people are already caffeinated and ready for work.
This sort of behavior won't sound unusual to countless college students or teenagers. But in the most severe cases of the syndrome, simply trying to go to bed earlier doesn't work, according to UCSD sleep researcher Dr. Dan Kripke.
"Some people are quite disabled by delayed sleep phase if their school work or employment requires them to get up early," he said. "They could voluntarily get up in the middle of their sleep period, but after a few days, they become so sleep-deprived, they can't continue to do it for the long run."
Perhaps 1 percent of the population has the disorder, Kripke said.
For reasons that aren't clear, it's much rarer for people to have the opposite condition -- advanced sleep-phase syndrome -- and be unable to postpone sleep past 7 or 8 p.m. Researchers elsewhere have already identified at least one of the genes that appear to cause that problem.
Extremely bright light boxes, which try to reset our internal clocks by making our bodies think it's morning, are a common treatment for sleep-phase disorders. Some patients take melatonin, a signaling hormone that can manipulate the body clock by tricking it into thinking it's dark and time for bed.
The University of Arizona's Klimecki suspects that, as in so many other medical conditions, sleep problems appear when genetics interact with other factors. Just as in illnesses like asthma, genetic predispositions don't necessarily doom someone to an unusual sleep pattern. Years ago, "we used to think of all these diseases as purely genetic," he said. "But now, we're realizing that the environment is really important as well."
Evolution could conceivably play a role too. Natural selection frequently affects both the development of diseases and resistance to them. For instance, an inherited trait that protected people from smallpox in the Middle Ages also appears to keep their descendents from getting AIDS. Klimecki pointed out that some blood disorders may have survived over time because they kept people from getting malaria.
But many more ailments appear to have developed independently from the pressures of evolution, and sleep problems may be among them, Klimecki said.
Once researchers figure out which genes affect sleep, they'll try to understand exactly how they affect the mysterious body clock, which typically resets itself after about 24 hours, and starts our daily cycles -- eating, sleeping and so on -- once again. Hence the term "circadian rhythm" -- "circadian" means "about a day."
Gene research in humans will also provide insight into the daily rhythms of animals.
"Nature uses the same genes and the same code to create the (body) clock in human beings as it does to create the clock in fruit flies," said Dr. Gregory Belenky, director of the Sleep and Performance Research Center at Washington State University at Spokane.
But body clocks aren't independent timekeepers: They depend on sunlight and darkness. In people who are kept away from the cues of light and dark, such as blind people, body clocks often boost the period of a "day" slightly beyond 24 hours, said Dr. Al Lewy, a sleep researcher at Oregon Health and Science University. In such people, the right time to go to sleep runs later and later each night, causing major disruptions to their lives. For the blind, who are immune to the effects of light boxes, melatonin may be the only treatment.
If researchers do get a handle on the genetics of sleep and the body clock, they may do more than produce gene-based treatments. According to Belenky, doctors could test people like pilots and special armed forces units to determine how they would handle sleep deprivation.
The tests might even give the lie to people who like to think they can easily skip sleep when they're actually not built to miss snooze time.
"People tend to think, 'Oh well, I'd like to get eight (hours), but I can manage with six,'" Belenky said. "But that's not true."
From yee Wiki:
Delayed sleep-phase disorder (DSPD), also known as delayed sleep-phase syndrome (DSPS) or delayed sleep-phase type (DSPT), is a circadian rhythm sleep disorder affecting the timing of sleep, peak period of alertness, the core body temperature rhythm, hormonal and other daily rhythms, compared to the general population and relative to societal requirements. People with DSPD generally fall asleep some hours after midnight and have difficulty waking up in the morning.
Affected people often report that while they do not get to sleep until the early morning, they do fall asleep around the same time every day. Unless they have another sleep disorder such as sleep apnea in addition to DSPD, patients can sleep well and have a normal need for sleep. However, they find it very difficult to wake up in time for a typical school or work day. If, however, they are allowed to follow their own schedules, e.g. sleeping from 4 a.m. to noon (04:00 to 12:00), they sleep soundly, awaken spontaneously, and do not experience excessive daytime sleepiness.
The syndrome usually develops in early childhood or adolescence. An adolescent version disappears in adolescence or early adulthood; otherwise DSPD is a lifelong condition. Depending on the severity, the symptoms can be managed to a greater or lesser degree, but there is no all-encompassing cure. Prevalence among adults, equally distributed among women and men, is approximately 0.15%, or 3 in 2,000. It is also genetically linked to ADHD by findings of polymorphism in genes in common between those apparently involved in ADHD and those involved in the circadian rhythm and a high proportion of DSPD among those with ADHD.
DSPD was first formally described in 1981 by Dr. Elliot D. Weitzman and others at Montefiore Medical Center. It is responsible for 7–10% of patient complaints of chronic insomnia. However, as few doctors are aware of it, it often goes untreated or is treated inappropriately; DSPD is often misdiagnosed as primary insomnia or as a psychiatric condition. DSPD can be treated or helped in some cases by careful daily sleep practices, light therapy, and medications such as melatonin and modafinil (Provigil). The former is a natural neurohormone responsible partly and in tiny amounts for the human body clock. At its most severe and inflexible, DSPD is a disability.
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http://en.wikipedia.org/wiki/Delayed_sleep_phase_disorder
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