A new study finds smokers who quit before the age of 40 can live almost as long as people who never smoked.
Researchers at the University of Toronto report quitting smoking before turning 40 gives back almost all of the 10 years that smoking generally cuts off a person's life span.
But that does not mean smoking is safe up until age 40. The study's lead researcher - Prabhat Jha, a University of Toronto professor and head of the Centre for Global Health Research at St. Michael's Hospital - said former smokers still have a greater risk of dying sooner than lifetime non-smokers.
"Now it's not true that the best thing to do is to smoke until 40 and quit. Because if you do that, you still have [...] at least 20 percent higher risk of dying if you have quit smoking by age 40," said Jha. "Now that's much lower than the risk of continuing to smoke, but it's still quite significant. In contrast, those that quit by age 30 basically are close to never-smoker rates, meaning they get almost all of that full decade of life back. So the key message is not that it's safe to smoke until age 40 and quit. The key message is: Don't smoke, and if you do smoke, quit as early as possible."
The researchers also found that women's risks of dying from smoking-related causes were 50 percent higher than what studies in the 1980s found. This most recent study looked at health and death records in the United States, but Jha said the findings can be applied worldwide.
"What smoking does is multiply the background rates of disease in any population upward. What this study adds, along with actually about three more recent studies, is that, that upward multiplication, if you will, of the risks is about threefold," Jha said. "So this suggests worldwide the risks are probably going to be as extreme. Basically, what we found is if women smoke like men, they die like men. And similarly if Indians smoke like Americans, they are going to die like Americans. If Chinese smoke like Americans, they are going to die like Americans."
Jha said just five countries - Brazil, China, Russia, Indonesia and India - are home to about half of the world's estimated 1.3 billion smokers. If the current trends continue, his report said smoking will kill about 1 billion people in the 21st century, a dramatic increase from 100 million in the 20th century.
The study was published on January 23 in the New England Journal of Medicine.