Lack of Sleep Linked to Medical Risks

睡眠不足 戕害你的健康

2013/07/18

Lack of Sleep Linked to Medical Risks 【By JANE E. BRODY／田思怡譯】 Millions of people unwittingly shortchange themselves on sleep. Research shows that most people require seven or eight hours of sleep to function optimally. Failing to get enough sleep can compromise health and even shorten life. The effects of inadequate sleep can profoundly affect memory, learning, creativity, productivity, emotional stability and physical health. Sleep specialists say a number of bodily systems are negatively affected by inadequate sleep: the heart, lungs and kidneys; appetite, metabolism and weight control; immune function and disease resistance; sensitivity to pain; reaction time; mood; and brain function. “Sleep affects almost every tissue in our bodies,” said Dr. Michael J. Twery, a sleep specialist at the National Institutes of Health in Maryland. Poor sleep is also a risk factor for depression and substance abuse. Levels of the hormone leptin, which tells the brain enough food has been consumed, are lower in the sleep-deprived while levels of ghrelin, which stimulates appetite, are higher. In addition, metabolism slows when sleep is disrupted; if not counteracted by increased exercise or reduced caloric intake, this slowdown could add up to four kilograms of weight gain in a year. The risks of cardiovascular diseases and stroke are higher in people who sleep less than six hours a night. A single night of inadequate sleep can cause daylong elevations in blood pressure in people with hypertension. Inadequate sleep is also associated with calcification of coronary arteries and raised levels of inflammatory factors linked to heart disease. ( Sleeping too much may also be risky. Higher rates of heart disease have been found among women who sleep more than nine hours nightly.) The risk of cancer may also be linked to sleep. A Japanese study of nearly 24,000 women ages 40 to 79 found that those who slept less than six hours a night were more likely to develop breast cancer than women who slept longer. Eva S. Schernhammer of Harvard Medical School found a link between levels of the sleep hormone melatonin and an increased risk of breast cancer. A study of 1,240 people at Case Western Reserve University in Cleveland, Ohio, found a higher risk of potentially cancerous colorectal polyps in those who slept fewer than six hours nightly. During sleep, the body also produces hormones that help fight infections and those that stimulate growth and repair cells. Dr. Vatsal G. Thakkar, a psychiatrist affiliated with New York University, recently described evidence associating inadequate sleep with an erroneous diagnosis of attention deficit hyperactivity disorder in children. In one study, 28 percent of children with sleep problems had symptoms of the disorder, but not the disorder. But some of the most insidious effects of too little sleep involve mental processes like learning, memory, judgment and problem-solving. During sleep, new learning and memory pathways become encoded in the brain, and adequate sleep is necessary for those pathways to work optimally. The cognitive decline that so often accompanies aging may in part result from chronically poor sleep. At checkups, tell your doctor how long and how well you sleep. Be honest: Sleep duration and quality can be as important to your health as your blood pressure and cholesterol level. 【2013-07-16/聯合報】

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