Women who quit smoking before the age of 40 can add an extra ten years to their lifespan, reveals a new study.

A team of researchers from the United Kingdom surveyed about one million women from the year 1996 to 2001. The participants of the survey were aged between 50 and 65 years. They were asked to fill up a questionnaire about their lifestyle, medical and social factors.

The study shows evidence to the harmful effects of smoking and the positive benefits of early cessation, both much greater than previously thought.

"Both in the UK and in the USA, women born around 1940 were the first generation in which many smoked substantial numbers of cigarettes throughout adult life," Sir Richard Peto, professor at the University of Oxford and one of the lead authors of the study, said in a statement.

"Hence, only in the 21st century could we observe directly the full effects of prolonged smoking, and of prolonged cessation, on premature mortality among women," he said.

At least 20 percent of the study participants were smokers, 28 percent were ex-smokers, and 52 percent had never smoked, when the survey began.

Three years later, researchers used National Health Survey (NHS) records to track the number of deaths in participants and to figure out the cause of death over an average 12-year period from the time the women joined the study.

They found that women who still smoked at the end of three years were three times more likely to die over the next 9 years as compared to non-smokers. Those women who quit smoking before reaching 40 years of age were 1.2 times more likely to die over the same period as compared to non-smokers, reported LiveScience. 

And those women who stopped smoking by the age of 30 could reduce 97 percent of the risk of death caused by smoking. However, experts warn that the results do not mean that women could continue smoking until the age of 40 before they give up smoking.

Experts also noted that the risk of smoking increased with the amount of cigarettes smoked. Death rates doubled even for light smokers, who smoked between one and nine cigarettes a day when compared with non-smokers.

The findings of the study, "The 21st century hazards of smoking and benefits of stopping: a prospective study of one million women in the UK," are published in the The Lancet journal.