And women who started smoking earlier in life were at a higher risk for overall mortality, of dying from respiratory disease and from any smoking-related disease.
However, a smoker's overall risk of dying returned to the level of a never-smoker 20 years after quitting. The overall risk declined 13 percent within the first five years of abstaining.
Most of the excess risk of dying from coronary heart disease vanished within five years of quitting.
For chronic obstructive pulmonary disease, the return to normal took almost 20 years, although there was an 18 percent reduction in the risk of death seen within five to 10 years after quitting.
And the risk for lung cancer didn't return to normal for 30 years after quitting, although there was a 21 percent reduction in risk within the first five years compared with women who continued to smoke.
Many previous studies on tobacco use had focused on men and on lung cancer, the authors stated. They also only looked at smoking status at the beginning of the study. "We got smoking information every two years, so we feel we have a more accurate estimate of current and past smoking," Kenfield said. "We saw increased risks for current smokers [than previous studies], and we think that's because we know who the current smokers are."
"This shows the power of quitting smoking," said Dr. Jay Brooks, chairman of hematology/oncology at Ochsner Health System in Baton Rouge, La. "We've known this for a number of years, but the beauty of this study is it is a very large and well-studied group of people. When I tell people to quit smoking, I say the effect of the heart precedes that of the lungs. If you've smoked, you need to be cognizant that you're still at an increased risk of lung cancer."
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