It takes around five years for the risk of coronary heart disease to reduce in women who stop smoking, but reducing the risk of lung and other cancers can take considerably longer.
These are the findings of a study published recently in the Journal of the American Medical Association and carried out by Stacey Kenfield and colleagues from Harvard. Researchers looked at data from the Nurses' Health Study for more than 100 000 women who were followed from 1980 to 2004. In this group there were nearly 12 500 deaths, with nearly 4500 among never smokers (36%), 3600 among current smokers (29%) and just under 4400 among past smokers (35%).
They found that there is a 13% reduction in the risk of death from any cause within the first five years of stopping smoking compared to continuing smoking. This risk reduces to the same as that of never smokers after 20 years. Vascular disease showed the most rapid reduction in risk - mainly withing the first five years. This includes coronary heart disease, for which 62% of the excess risk was gone within the first five years after stopping and cerebrovascular disease, in which 42% of excess risk was gone within the first five years. Death from respiratory disease showed an 18% reduction in the first five years, going down to the never smokers' level after 20 years.
However, the risk of death from lung cancer, while it went down by 21% in the first five years, took 30 years to level with the risk of never smokers. Past smokers who had stopped for 20 years, but for less than 30 years had an 87% reduction in the risk of lung cancer, compared with women who are still smoking.
The risk of death from all causes, including respiratory and cardiovascular was higher among women who had started smoking at younger ages. Smoking appears to be linked to an increased risk of colon cancer, but not to ovarian cancer risk.
About 64% of deaths among current smokers and 28% among previous smokers were linked to smoking.
