It's Never Too Late to Kick the Habit.
Aug. 2, 2000 -- You're never too young or too old to stop smoking. Quitting by age 30 eliminates 90% of tobacco-related cancer risk -- but quitting even at age 60 still cuts this risk significantly, according to a report in the current issue of the British Medical Journal.
A half-century ago, the lead authors of the new report were among the first to prove that cigarette smoking causes lung cancer. By comparing these old findings to new ones from a large 1990 study, they were able to calculate the risks of prolonged smoking -- as well as the benefits of quitting.
"The 1950 paper was written when the tobacco-smoking epidemic was at a very early stage," lead researcher Richard Peto, professor of statistics at England's Oxford University, tells WebMD. "Most women had not been smoking long enough to do themselves in. But by the 1990s, those who have been smoking have been smoking throughout their entire adult lives. Also, people now are trying to quit, so effects of prolonged cessation are apparent. Essentially, what we can do now is assess the effects of very prolonged smoking."
The new analysis offers some intriguing insights:
- Smoking eventually kills about half of those who never quit.
- Smokers who started smoking before the age of 15 have twice the risk of lung cancer of those who started smoking after 20.
- Lung cancer kills nearly 16% of men who never quit.
- Fewer women quit smoking than men. Among those still smoking in 1990, more women smoked heavily than in 1950, and more started smoking before age 20.
- For both men and women who continue to smoke, the risk of lung cancer increased substantially from 1950 to 1990. This appears to be due to the fact that smokers consume more cigarettes than they used to.
Experts who commented on the study for WebMD say the findings give people who smoke a new reason to stop. David C. Christiani, MD, tells WebMD that the new study comes as no surprise -- it confirms many other studies from both the U.S. and the U.K.
"I think this study is terribly important motivation for smoking cessation," says Christiani, professor of occupational medicine and epidemiology at the Harvard School of Public Health in Boston. "It's never too late to decrease your cancer risk. You should stop smoking, whatever stage of life you are in."
Joseph R. Landolph Jr., PhD, is associate professor of molecular microbiology, immunology, and pathology at the University of Southern California's Norris Cancer Center. He tells WebMD that tobacco smoke contains not only carcinogens -- substances that make normal cells turn into cancer cells -- but also substances that speed up the carcinogenic process, called tumor promoters.
"There is a point at which, if you interrupt the tumor promotion, the tumor will go away," Landolph says. "Beyond that point, quitting probably won't stop tumor growth. When you keep adding tobacco smoke, you keep adding carcinogens -- and whatever it is that is in there that promotes tumors."
Peto says that in the 1950s and 1960s, the U.K. had the world's highest rate of smoking-related lung cancer. While smoking remains the greatest single cause of premature death in that nation, the current death rate among middle-aged residents has decreased by half.
"Now we've actually got the best decrease in tobacco-related deaths in the world," Peto says. "We have twice as many ex-smokers as smokers. Of those who have ever smoked cigarettes, two-thirds of the over-50s have quit cigarette smoking, and two-thirds of the remaining third wish they could get off it."