FAITH LAPIDUS: This is SCIENCE IN THE NEWS, in VOA Special English. I'm Faith Lapidus.
BOB DOUGHTY: And I'm Bob Doughty. This week, we talk about smoking – the leading cause of cancer worldwide.
FAITH LAPIDUS: Barack Obama completed his first routine physical examination as President of the United States last week. Doctors reported that Mister Obama is in excellent health. They say all evidence suggests that he will remain so during his presidency.
The doctors gave the president suggestions so that he can stay healthy. One is for him to continue with efforts to stop smoking. Mister Obama has spoken publicly about those efforts in the past. The new report shows his battle against smoking is continuing.
BOB DOUGHTY: President Obama is not alone. More than one billion people around the world are smokers. Health experts have been warning about links between smoking and disease for years.
Smoking kills an estimated five million people worldwide every year. Experts say smoking is the leading cause of preventable death. And, it is the second leading cause of death, after cancer.
Smoking is also the leading cause of cancer. Experts say forty percent of cancers could be prevented by avoiding health risks like smoking and tobacco use.
Smoking also causes forty-two percent of cases of chronic respiratory disease, including asthma, bronchitis and emphysema. And, it causes ten percent of cardiovascular diseases, like heart disease and stroke.
FAITH LAPIDUS: The medical research community is continually reporting reasons why smokers should stop. A recent study found that people who smoke are nearly two times as likely as non-smokers to develop Alzheimer's disease. Alzheimer's weakens or destroys memory and reasoning.
In the study, researchers examined forty-three published studies about the link between Alzheimer's disease and smoking. They found that smoking increased the risk of Alzheimer's developing by one and seven-tenths percent. The researchers work at the University of California in San Francisco. Their findings were published in the Journal of Alzheimer's Disease.
In an earlier study, seven thousand people were observed for an average of seven years. Each person was fifty-five years or older. Those who smoked were fifty percent more likely to develop memory loss than those who never smoked, or who had quit.
BOB DOUGHTY: Other research has linked smoking to Amyotrophic Lateral Sclerosis. ALS is a deadly disease affecting the motor nerves and the voluntary muscles. Last year, a study in the medical journal Neurology found smoking to be an established risk factor in developing the disease. Some of the evidence even suggested smoking may be directly responsible for ALS.
Smoking also increases the risk of developing age-related macular degeneration. AMD is the leading cause of blindness among adults fifty and older. Research has shown AMD is two to three times more common among smokers than other people.
FAITH LAPIDUS: A recent study examined how smoking affects a person's risk of AMD later in life. Researchers at the University of California in Los Angeles studied nearly two thousand women.
Four percent of the women were smokers. Each woman had pictures of her retinas taken at age seventy-eight. The researchers compared these retinal images with pictures taken five years later when the women were eighty-three. They studied the pictures for signs of AMD and to see whether smoking influenced the women's chances of developing the disease.
The women who smoked had an eleven percent higher rate of AMD than the other women. In women over eighty, those who smoked were five and a half times more likely to develop AMD than the women who did not smoke. A report on the study was published in the American Journal of Ophthalmology.
BOB DOUGHTY: People who smoke are not only hurting themselves. They also can harm non-smokers. The World Health Organization estimates that secondhand smoke kills six hundred thousand people each year.
The International Union Against Cancer says about seven hundred million children breathe smoke-filled air. Expectant mothers who smoke are more likely to have babies with health problems and low birth weight. Such babies may suffer health problems as they grow.
FAITH LAPIDUS: Even after all the warnings, the WHO says one billion three hundred million people still smoke. The number of smokers is expected to grow to one billion seven hundred million by twenty twenty-five. Smoking rates have decreased in the United States and Europe. But rates have risen in other areas.
WHO officials say eighty-four percent of all smokers live in developing countries. Nations in the Western Pacific Ocean have the highest smoking rates. One-third of all smokers live in East Asia and the Pacific. The area has the largest number of male smokers. It also has the fastest growing number of female and child smokers. Every day, diseases linked to tobacco use kill more than three thousand people in the area.
BOB DOUGHTY: Scientists have found more than four thousand chemicals in cigarette smoke. At least two hundred fifty of them are known to be harmful. And, fifty have been found to cause cancer. They include arsenic, which can be used to kill plants and small animals. Cigarette smoke also contains formaldehyde – a liquid used to protect the look of dead bodies.
As bad as those chemicals are, nicotine may be the most threatening of them all. Nicotine is a poison found in tobacco. It gives smokers pleasure and keeps them coming back for more.
The body grows to depend on nicotine. Studies have found that nicotine can be as difficult to resist as alcohol or the drug cocaine. Experts say nicotine can kill a person when taken in large amounts. It does this by stopping the muscles used for breathing.
FAITH LAPIDUS: Menthol cigarettes are said to be no safer than other tobacco products. Menthol cigarettes produce a cool feeling in the smoker's throat. This may cause people to hold the smoke in their lungs longer than smokers of other products. As a result, scientists suspect that menthol cigarettes may be even more dangerous than other cigarettes.
Some smokers believe that cigarettes with low tar levels are safer. Tar is a substance produced when tobacco leaves are burned. It is known to cause cancer. America's National Cancer Institute has said that people who smoke low-tar cigarettes do not reduce their risk of getting diseases linked to smoking.
BOB DOUGHTY: So is there any way to smoke without harming your health? The majority of available research suggests not. Smoking even a few cigarettes can be dangerous. But, many of the harmful effects of smoking ARE reversible. They can be undone. That is why most medical experts advise people to stop smoking forever.
The American Cancer Society says blood pressure returns to normal twenty minutes after the last cigarette. Carbon monoxide levels in the blood return to normal after eight hours. The chance of heart attack decreases after one day. After one year, the risk of heart disease for a non-smoker is half that of a smoker.
FAITH LAPIDUS: There are many products available to help people reduce their dependence on cigarettes. Nicotine replacement products provide the body with small amounts of the chemical through forms other than cigarettes. The amounts of nicotine are slowly reduced over time.
Chantix and Zyban are two prescription medicines that have also been shown to help smokers quit. They do not contain nicotine. Chantix works on nicotine receptors in the brain to reduce the urge to smoke. Zyban works by increasing levels of dopamine in the brain. Dopamine is a chemical that produces pleasure.
BOB DOUGHTY: People who have quit smoking offer this helpful advice to those who want to stop. Stay away from alcohol. Take a walk instead of smoking. And, avoid people who are smoking. If possible, stay away from situations that trouble you. It is not easy to quit smoking. And, people never can completely control their own health. But as one doctor advises her patients, becoming a non-smoker is one way to gain control of your life.
This SCIENCE IN THE NEWS was written by June Simms. Brianna Blake was our producer. I'm Faith Lapidus.
And I'm Bob Doughty. Join us again next week for more news about Science in Special English on the Voice of America.