Deaths from vascular disease due to smoking are substantially reduced in women within 5 years after they quit smoking, according to findings from the Nurses' Health Study.
"Because there is a rapid decline in risk for some diseases, it's never too late to quit smoking," Dr Stacey A. Kenfield told Reuters Health.
On the other hand, "A former smoker's risk for some diseases does not decline to the level of non-smokers for 20 or more years, so it is never too early to quit smoking, either."
Kenfield, at the Harvard School of Public Health in Boston, and her team analysed outcomes for 104 519 women from the time they entered the Nurses' Health Study in 1980, at ages 34 to 59 years, through 2004.
Death risk increase 3-fold
As reported in the Journal of the American Medical Association, a total of 12 483 deaths occurred. The risk of dying from any cause was nearly 3-fold higher among current smokers than for never-smokers, and the risk of dying from smoking-related cancers was increased 7-fold.
However, after quitting for 5 years, mortality due to coronary heart disease is reduced by almost half, and mortality from lung cancer is about 20 percent lower.
"This rapid decline in risk for some diseases can help provide motivation to (smokers) who are thinking about quitting," Kenfield said.
Her group found that the risk of developing chronic obstructive lung disease, such as emphysema, decreased to the level of non-smokers by 20 years after quitting, and by 30 years for lung cancer.
"Importantly, we found a 58 percent increase in risk of dying from other cancers that are not thought to be associated with smoking," Kenfield added. "One of these cancers is colorectal cancer, where current smokers had a 63 percent increased risk of dying and former smokers had a 23 percent increased risk of dying, compared to non-smokers."
Benefits of public health initiatives
Public health initiatives to keep teenagers from smoking should considerably reduce mortality as well. The researchers found that postponing the age at which people start smoking "had a huge impact on reducing risk of respiratory diseases and smoking-related cancers."
The team believes their findings can also be applied to men.
"Data on the speed at which risk decreases after stopping may help smokers understand the value of stopping smoking and the health benefits they will gain from succeeding," Kenfield concluded. – (Karla Gale/Reuters Health)
SOURCE: Journal of the American Medical Association, May 7, 2008.
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