A large trial, involving more than 100,000 women, saw significant declines in several death risks within 5 years of putting out the last cigarette.

This is undoubtedly welcome news for many female smokers, as it shows that the dangers of smoking are reversible and can decline to the level of nonsmokers. This does not happen over night though, as for some conditions like lung cancer, it can take as long as 30 years of no smoking to equalize the risk.

Cigarette smoking is the leading preventable cause of premature death in the United States. It accounts for almost 500,000 deaths in USA each year. Studies have shown, that possibly as many as 5 million years of life are lost to smoking every year in US alone. Smoking causes lung cancer, heart disease and a number of other cancers and respiratory diseases.

Over the 22 year duration of the study, women smokers were shown to have almost triple the risk of overall death compared with women who had never smoked. There was a significant association between smoking and colon cancer (a 63 % increased risk compared to nonsmokers), however the link between smoking and ovarian cancer was not shown to be significant.

Within the first 5 years of abstaining, women have a 21 % reduced risk of dying from coronary heart disease and lung cancer. Within 5 to 10 years after quitting, they also enjoy an 18 % reduction in the risk of developing chronic obstructive pulmonary disease (COPD).

The earlier a women starts smoking, the higher the risk of overall mortality from smoking-related diseases. A good incentive to stop smoking is that the overall risk of death declines 13 % within the first 5 years of abstaining and it reaches the level of a never-smoker 20 years after extinguishing the last cigarette.

"It's never too early to stop, and it's never too late to stop," added Kenfield, who is a postdoctoral research fellow at the department of epidemiology at the Harvard School of Public Health in Boston.

Sources: Women Who Quit Smoking Lower Heart Risks Quickly (MedlinePlus), Smoking Resource Center (Medscape)