Monday, January 27, 2014 C7
HEALTH LAB REPORT
Snooze it
........................................... Jeanette Wang jeanette.wang@scmp.com
or lose it
A good night’s sleep allows the brain to cleanse itself, but too much might be worse than too little, David Tan discovers
S
leep – we all love it but we typically don’t get enough of it. In bustling cities such as Hong Kong, where life is fast and furious, sleep can seem like a luxury left to be savoured only on weekends and holidays. We all know that sleep is good for us, and now scientists in the US report new evidence why: the brain changes when we sleep to clean out harmful toxins that have built up during the day. Lulu Xie and fellow neuroscientists at the University of Rochester Medical Center used new medical imaging techniques to observe the brains of nice that were either asleep or awake. Scientists knew that the amount of energy consumed by the brain does not decrease much while we sleep, but they did not know how that energy was being used. The brain has a unique method of waste removal, known as the glymphatic system, a kind of plumbing system that washes away toxins by pumping cerebral spinal fluid (CSF) through spaces between brain cells. Interestingly, Xie and colleagues found that the glymphatic system was almost 10 times more active during sleep. In addition, they saw that cells in the brain “shrank” by 60 per cent during sleep. This contraction creates more space between the brain cells and allows CSF to wash more freely through the brain tissue. By contrast, when the brain is awake, cells are closer together, restricting the flow of CSF. CSF washes away toxic metabolites, degradation products that brain cells secrete during regular tasks in waking hours. The timely removal of waste from the brain is essential because accumulation of toxic proteins such as beta-amyloid can lead to Alzheimer’s disease. In fact, almost every
neurodegenerative disease is associated with the accumulation of cellular waste products. By tagging beta-amyloid with fluorescent tags, the scientists saw that this waste protein flowed out of the brain twice as fast during sleep. In fact, the flow of waste out of the brain during the waking state was only 5 per cent of that when the mice were asleep. “This study shows that the brain has different functional states when asleep and when awake,” says Dr Maiken Nedergaard, who supervised the study. “In fact, the restorative nature of sleep appears to be the result of the active clearance of the by-products of neural activity that accumulate during wakefulness.” Importantly, the brain can only clean itself during sleep. “The brain only has limited energy at its disposal and it appears that it must choose between two different functional states: awake and aware, or asleep and cleaning up,” says Nedergaard. “You can think of it like having a house party. You can either entertain the guests or clean up the house, but you can’t really do both at the same time.” In addition to detoxification, the brain also produces brain support cells during sleep. Known as oligodendrocytes, these
It’s critical that adults aim for seven to nine hours of sleep each night DR M. SAFWAN BADR
support cells produce myelin that wraps around neurons and allows electrical impulses to move rapidly between them, similar to how insulation works around electrical wires. Dr Chiara Cirelli from the University of Wisconsin, Madison, reported in September that during sleep, genes promoting myelin formation were switched on and the reproduction of oligodendrocyte precursor cells (OPCs) doubled. The growth of OPCs was particularly high during the rapid eye movement (REM) stage of sleep, which is associated with dreaming. “It is clear that the way other supporting cells in the nervous system operate changes significantly depending on whether the animal is asleep or awake,” says Cirelli. Sleeping not only consolidates memory of the day’s events, it also helps improve learning, for example, of movement tasks such as playing the piano. Using three different kinds of brain scans, researchers from Brown University in the US identified exact locations of brain activity during sleep after learning a finger-tapping task, and quantified changes among brainwaves in these regions. The supplementary motor area (SMA), a region on the topmiddle of the brain, was found to be the site of brainwave changes. Specifically, these changes were in fast-sigma and delta brainwave oscillations, which govern changes within the SMA and also changes in the SMA connectivity to other brain areas. “It’s an intensive activity for the brain to consolidate learning and so the brain may benefit from sleep, perhaps because more energy is available or because distractions and new inputs are fewer,” said Dr Yuka Sasaki, who led the study.
A common But it turns out treatment for too much sleep is sleep apnea is also harmful. A known as new study by the continuous Centers for The age at which too little or positive airway Disease Control too much sleep becomes pressure (CPAP) Prevention (CDC) bad for you treatment, which in the US links too can stop snoring, little sleep (six reduce blood pressure hours or less) and and improve daytime too much sleep alertness. (10 hours or more) with chronic Patients who have undergone diseases in adults aged 45 years CPAP treatments for several and older. months were found to also have Published in early October specific improvement in facial this year, the study involved more appearance. In other words, than 54,000 participants in 14 sleeping better made these states in the US. Both short and patients look better. long sleepers reported a higher Doctors at the University of prevalence of coronary heart Michigan used a variety of ways disease, stroke, diabetes, obesity to assess appearance. Firstly, and anxiety, compared to optimal they used a precise facesleepers who got seven to nine measuring system called hours of shut-eye on average. photogrammetry to assess tiny In fact, for long sleepers, the differences in facial contours association with coronary heart before and after CPAP treatment. disease, stroke and diabetes was They also mapped the colours even stronger with more sleep. of patients’ facial skin. Finally, a “Sleeping longer doesn’t mean subjective test of appearance was that you’re sleeping well. It is used in which 22 independent important to understand that raters were asked to rank the both the quality and quantity of attractiveness, alertness and sleep impact your health,” says Dr youthfulness of patients by Safwan Badr, president of the looking at photos, without American Academy of Sleep knowing which were “before” and Medicine (AASM). which were “after”. “It’s critical that adults aim for The overall result of the study seven to nine hours of sleep each was that patients appeared more night to receive the health alert, more youthful and more benefits of sleep, but this is attractive after sleep treatment, especially true for those battling a and objective measures of facial chronic condition,” he adds. appearance showed less redness Getting the optimal amount of and puffiness. sleep is not only good for our And so scientific research health, but also apparently for returns the verdict that the right our looks. Sleep apnea is a amount of sleep is good for our condition where snoring and brains and improves our looks. breathing interruptions disrupt The next time you’re faced sleep, preventing patients from with the dilemma of going to bed getting a good night’s rest. or squeezing in a little more work, Affecting millions of adults, you now know the reasons why most of whom remain you should choose sleep. Sweet undiagnosed, sleep apnea dreams. increases the risk of heart-related life@scmp.com problems and daytime accidents.
45
FDA drug approvals not equal While survey data shows that patients expect drugs approved by the US Food and Drug Administration to be both safe and effective, a new study questions this assumption. Researchers at the Yale School of Medicine show in a study published in the journal JAMA that the clinical trials used by the FDA to approve new drugs between 2005 and 2012 vary widely in their thoroughness. A third of the drugs in the study period were approved on the basis of a single trial, without replication. “There was a lack of uniformity in the level of evidence the FDA used,” says study senior author Dr Joseph Ross, assistant professor of internal medicine at Yale School of Medicine.
Icy technique improves robotic kidney transplants A collaboration of surgeons at Henry Ford Hospital and Medanta Hospital in India successfully transplanted kidneys into 50 recipients using an innovative robotassisted procedure in which the organ is cooled with sterile ice during the operation. This gave the surgeons more time to safely learn and perfect the minimally invasive robotic surgery, which is a boon to ill and weakened transplant recipients who are at greater risk of complications. None of the study patients developed blood or urine leaks, infections or other complications from their surgical wounds. None required dialysis after surgery. The researcher project was published online in European Urology.
Folic acid promotes growth of breast cancer in rats Folic acid supplements at levels consumed by breast cancer patients and survivors in North America promoted the growth of existing breast cancer in rats, new research published in the online journal PLOS ONE has found. Researchers at St Michael’s Hospital have shown that folic acid supplements in doses 2½ to five times the daily requirement “significantly promotes” the growth of existing precancerous or cancerous cells in the mammary glands of rats. The role of folate in the development and progression of breast cancer is highly controversial; some studies have found it may offer protection against the cancer.
Photo: Corbis
HITS AND MYTHS
Jump away – your appendix will be fine ................................................ Sasha Gonzales life@scmp.com Q: Can jumping around or exercising after eating give you appendicitis? The straight answer: No The facts: Appendicitis is a painful condition that can affect anyone, but it mostly tends to occur in people aged between 10 and 30. It is also one of the most common reasons for emergency abdominal surgery. Appendicitis occurs when the appendix, a 10cm-long, worm-shaped
structure that extends from the large intestine, becomes swollen, inflamed and filled with pus. Symptoms of the condition typically present as an aching, rapidly worsening pain that begins at the navel and shifts to the lower right abdomen, tenderness in the lower right abdominal area, vomiting and nausea, low-grade fever and chills, constipation or diarrhoea, bloating and an inability to pass gas. If untreated, appendicitis can be fatal as the appendix can burst. However, in most cases, surgery is performed or antibiotics are prescribed before the condition reaches the
dangerous stage, so deaths from the condition are extremely rare these days. The appendix was previously believed to be a vestigial organ (an organ that serves no purpose). But now, scientists have theorised that it is a factory and storehouse for beneficial bacteria, which get released when our bodies are battling a serious infection, such as diarrhoea. It is not entirely clear what causes appendicitis, although there is no evidence to suggest that it is associated with jumping around or exercising after eating, says Dr Renny Yien, a specialist
The causes of appendicitis are not entirely clear.
in general surgery at Matilda International Hospital. Experts believe that appendicitis has two likely causes. The first is an infection that has found its way to the appendix, causing it to become inflamed. The second possible cause is obstruction by a hard piece of stool. When this faecal stone gets trapped in the appendix, bacteria begin to grow and multiply, causing the appendix to fill up with pus and become inflamed. According to Yien, other potential sources of such a blockage include types of inflammatory bowel disease, such as Crohn’s disease or
ulcerative colitis. Obstruction may also occur if the lymph nodes in the appendix swell. Among the less common causes of blockage: fruit and vegetable seeds, stomach worms, thickened barium from previous X-rays, and, in the elderly, cancer of the colon. Although the appendix is now thought to be part of the lymphatic system as it plays an important role in intestinal health, there is no cause for concern if you have already had yours removed, since the appendix is not the only part of the body that produces beneficial bacteria.