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BOB DOUGHTY: This is SCIENCE IN THE NEWS in VOA Special English. I'm Bob Doughty.
BARBARA KLEIN: And, I'm Barbara Klein. Today, we will tell about stress and its effects on human health. Stress is a condition resulting from mental or emotional tension. It is how your body reacts to physical, chemical and other influences.
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BOB DOUGHTY: Stress affects everybody, every day. There is no way to avoid it. One of the first people to study the condition was Hans Selye of Canada. He said the only way to escape stress is death.
Professor Selye found there are two kinds of stress. He said one kind is good for us. He called this stress, eustress. This type of stress is linked to fun, exploration or excitement. Eustress is the stress you experience from riding a roller coaster or meeting a goal. It can keep our bodies and minds strong. It gives us the push we need to deal with an urgent situation.
BARBARA KLEIN: Negative or bad stress is often called distress. Too much of it can be harmful. Some of the leading causes of stress include the death of a loved one, ending a marriage, sickness and financial problems.
Many Americans say a leading cause of their stress is the current economy. High unemployment rates and job cuts have caused concerns about the future. Last month, one study found that 62 percent of Americans believe economic conditions are getting worse. Forty-seven percent of those asked described current economic conditions as poor. A year earlier, 44 percent gave economic conditions a poor rating. The Gallup Organization reported the information.
A separate study found that 75 percent of American workers and retirees are very concerned about their financial future. One-third of those asked said stress levels about their financial situation are much higher now than a year ago. The Principal Financial Group announced the results of the study.
BOB DOUGHTY: Medical studies have shown that too much stress can weaken the body's ability to fight disease. It may make an existing health problem worse. Or it can lead to sickness or serious health problems.
For example, your body reacts to stressful situations by raising your blood pressure and making your heart work harder. This is dangerous if you already have high blood pressure or heart disease.
BARBARA KLEIN: Anything you see as a problem can cause stress. It can result from everyday situations or major problems. Stress results when something causes your body to act as if it is under attack. Causes of stress can be physical, such as injury or disease. They can also be mental, like problems involving your family, job, health or finances.
The tension of stress can interfere with sleep or cause anger or sadness. A person may become more forgetful or find it harder to think clearly. Losing one's sense of humor is another sign of an unhealthy amount of stress.
Many people who feel stressed may take on harmful behaviors in an attempt to deal with the stress. This includes eating too much, drinking too much, smoking more or using drugs. All of these things can lead to other problems.
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BOB DOUGHTY: Chronic stress happens often or lasts a long time. Chronic stress causes the body to produce too much of two hormones, cortisol and adrenalin. Cortisol is called the "worry" hormone. It is produced when we are afraid. Adrenalin prepares the body to react physically to a threat.
Persons with chronic stress produce too much of these hormones for too long. Too much cortisol and adrenalin can result in physical problems and changes that lead to stress-related disorders.
Cortisol provides high levels of energy during important periods. However, evidence shows that extended periods of cortisol in the body weakens bones, damages nerve cells in the brain and weakens the body's defense against disease.
BARBARA KLEIN: A recent study linked high levels of cortisol to a major increase in death from cardiovascular disease years later. Researchers examined 861 adults aged 65 and older. They measured the levels of cortisol in each person's urine over a 24 hour period. They then followed the group's members for about six years.
During that time, 183 of the individuals died. The researchers said those with the highest level of cortisol were five times more likely to die from cardiovascular causes than those with the lowest levels. The Journal of Clinical Endocrinology & Metabolism published the findings.
BOB DOUGHTY: Researchers at the University of Western Ontario carried out a similar study involving levels of cortisol in hair. Their study reached similar findings. The researchers said the hair cortisol levels were a better predictor of heart attack than established risk factors like high blood pressure.
High stress levels have also been found to cause asthma attacks, head pain, difficulty sleeping, stomach problems and skin disorders. Stress is also linked to mental conditions like depression and anxiety disorders.
Studies show that chronic stress reduces the levels of the hormone estrogen in women. This might put some women at greater risk for heart disease or the bone-thinning disease osteoporosis.
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BARBARA KLEIN: Mental and health experts believe personality is an important part in how we experience stress. Personality is the way a person acts, feels and thinks.
Some people are aggressive and always in a hurry. They often become angry when things do not happen the way they planned. They are called "Type A" personalities. Studies suggest that these people often get stress-related disorders.
The "Type B" personality is calmer. These people are able to deal with all kinds of situations more easily. As a result, they are less affected by stress.
BOB DOUGHTY: Studies have shown that men and women deal with stress differently. Women seem to be better able to deal with stress than men are. However, experts say women are three times more likely to develop depression in reaction to the stress in their lives.
American writer John Gray became famous for his book, "Men are from Mars, Women are from Venus." He says one major difference between men and women is the way they react to the hormone testosterone. The body releases this hormone to deal with stressful situations. Mr. Gray says studies have linked a rise in testosterone levels to reduced stress in men. However, high testosterone levels have no such effect on women.
He notes that men and women also have opposite ways of dealing with stress. For a man, the best way is to rest and forget about daily problems. But a woman suffering from stress needs to talk about her problems. Talking leads to the release of the brain hormone oxytocin, which lowers her stress levels.
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BARBARA KLEIN: Experts say there are several ways to deal with stress. They include deep breathing and a method of guided thought called meditation. They also include exercise, eating healthy foods, getting enough rest and balancing the time spent working and playing.
Doctors say people should limit the amounts of alcohol and caffeine in their diets. People who have many drinks with caffeine, like coffee, experience more stress and produce more stress hormones.
Exercise is one of the most effective stress-reduction measures. Running, walking or playing sports causes physical changes that make you feel better. Exercise also improves the body's defense system against disease. And studies have found that it helps protect against a decrease in mental ability.
BOB DOUGHTY: Doctors say deep, slow breathing is also helpful. Many medical studies have shown that clearing the mind through quiet meditation helps you become calm. This causes lower blood pressure, reduced muscle tension and decreased heart rate.
Experts also say keeping stress to yourself can make problems worse. Researchers have linked the failure to identify and express emotions to many health conditions. These include eating disorders, fear disorders and high blood pressure.
They say expressing emotions to friends or family members or writing down your feelings can help reduce stress. Experts say people should attempt to accept or change stressful situations whenever possible.
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BARBARA KLEIN: This SCIENCE IN THE NEWS was written by George Grow and June Simms, who also was our producer. I'm Barbara Klein.
BOB DOUGHTY: And I'm Bob Doughty. Join us again next week for more news about science in VOA Special English.
cortisol: 皮质醇
adrenalin: 肾上腺素
estrogen: 雌激素
osteoporosis: a condition in which the bones become weak and are easily broken（骨质疏松；骨质疏松症）
testosterone: a hormone produced in men's testicles that causes them to develop the physical and sexual features that are characteristic of the male body（睾酮；睾丸素）
oxytocin: 催产素
（来源：VOA 编辑：陈丹妮）
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