People who have spent most of their lives smoking may derive health benefits within five years of quitting - drastically reducing their chance of dying from a heart attack, stroke or lung cancer, according to a study published today.
In just five years, quitters reduced their added risk of dying of a heart attack by 47 percent and of lung cancer by 21 percent. Over time, their risk declined to the level of nonsmokers.
The message: There is hope for even the most inveterate smokers.
"Many people think there's just nothing they can do," said Stacey A. Kenfield, an epidemiologist with the Harvard School of Public Health. "But even in the short term, we do see benefit for some diseases, and it's worth it even if you're 70 years old and you've been smoking all your life."
The analysis, published in today's Journal of the American Medical Association, is the most complete picture to date of the health effects of quitting, some experts said.
One hope for quitters is a new vaccine designed to block the pleasure of smoking. At a conference in Baltimore yesterday, the vaccine's Rockville-based maker reported that 16 percent of volunteers in a clinical trial were able to quit after repeat inoculations, compared with 6 percent of those who got a placebo.
About 42 million Americans smoke cigarettes, and 440,000 people die each year from effects of the habit - accounting for one in five American deaths, according to the U.S. Centers for Disease Control and Prevention.
In the Harvard study, researchers followed more than 100,000 female nurses between 1980 and 2004, asking them every two years to answer questions, including their smoking status and history of chronic diseases. The research was part of the Harvard Nurses' Study, one of the largest and longest-running observational studies of risk and women's health.
Among other findings, the researchers learned that people who quit smoking lowered their risk of dying of any cause by 13 percent in the first five years. By the 20th year, their risk was the same as people who had never smoked.
It took 20 years of abstinence to erase the elevated risk of dying from a smoking-related cancer and 15 to 20 years to erase the increased risk of a fatal heart attack. But most of the benefit to the heart occurred in the first five years, in contrast with the lungs, where the benefit occurred more gradually.
Kenfield said many of the women she had interviewed reported a quick improvement in quality of life. "There is definitely an immediate benefit of quitting, such as being able to breathe better because you have less carbon monoxide," she said. "Your heart rate goes down, your blood pressure goes down, you have better circulation."
Making inroads into chronic diseases is more complicated.
Smoking damages the cardiovascular system in several ways. It interferes with natural chemicals that keep blood vessels open and prevent harmful clots. It also reduces levels of good cholesterol and makes bad cholesterol more likely to do harm.
"You stop smoking, and basically you're reversing this process," said Dr. Michael Miller, director of preventive cardiology at the University of Maryland Medical Center. "It's like taking away a natural stimulant."
Years of smoking subjects the lungs to carcinogens that can damage the DNA in cells. For a single cell to turn cancerous, it takes an accumulation of genetic changes - a process that occurs over time.
"By stopping, you don't accumulate more damage," said Dr. James Hermann, an associate professor of oncology at the Johns Hopkins Kimmel Cancer Center. "There's still some damage that's occurred in some of the smokers already, but at least you don't incur more."
Some may quit in time to prevent the final insult that tips a cell into a cancerous state. For some, quitting may come too late: The final injury has already occurred, even though the person might not yet have symptoms. But as a general rule, "The longer you've quit, the better; the less you've smoked, the better," Hermann said.
The Harvard researchers calculated the risk of dying according to the severity of a person's smoking habit. Women with a 40-year habit of at least 35 cigarettes (almost two packs) a day were 114 times more likely to die of emphysema or chronic bronchitis than nonsmokers. If they smoked fewer than 15 cigarettes daily, their risk was 23 times that of a nonsmoker.
Women who smoked 35 cigarettes daily were 40 times as likely to die of lung cancer and almost five times as likely to die of a heart attack as nonsmokers. If they smoked the lesser number, they were almost 12 times as likely to die of lung cancer, and three times as likely to die of a heart attack.
Meanwhile, researchers from Rockville-based Nabi Biopharmaceuticals reported results of a six-month trial yesterday at the annual vaccine conference of the National Foundation for Infectious Diseases in Baltimore.
The vaccine, called NicVAX, is designed to trigger antibodies that bind to nicotine as it enters the bloodstream. Together, the antibodies act like a giant sponge, soaking up nicotine before it binds. In the trial, 301 volunteers were given five injections over six months and had their smoking habits tracked for a year.
Sixteen percent of the 201 volunteers who got the medication managed to quit smoking for a full year, compared with only 6 percent of the 100 volunteers given a placebo, company officials said.
A booster shot might be necessary if people get nicotine cravings after extended periods, a company official said.
The company expects to begin a larger trial later this year and seek government approval sometime after that for a product that would be given in a doctor's office.
Sun reporter Dennis O'Brien contributed to this article.