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Study pinpoints effect of quitting smoking on mortality


Women who stop smoking before age 40 avoid more than 90% of the increased risk of dying caused by continuing to smoke, according to a study

The hazards of smoking for women are far greater than previous studies have suggested, but stopping smoking has bigger benefits than previously thought, reported researchers with Oxford University.

Two-thirds of all deaths of smokers in their 50s, 60s, and 70s can be ascribed to smoking, the results indicated, since most of the difference between smokers and non-smokers comes from smoking-related diseases such as lung cancer, chronic lung disease, heart disease and stroke.

Stopping smoking around age 30 is even more beneficial than stopping at age 40: It allows women to avoid 97% of the increased risk of premature death due to cigarettes, according to the study.

“Both in the U.K. and the U.S.A., women born around 1940 were the first generation in which many smoked substantial numbers of cigarettes throughout adult life,” Sir Richard Peto, an Oxford professor and one of the study’s lead authors, said in a news release. “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.”

Peto said male or female smokers who “stop before reaching middle age will on average gain about an extra 10 years of life.”

The Million Women Study recruited 1.3 million women ages 50 to 65 in the years from 1996 to 2001. Participants completed a questionnaire about their lifestyle, medical and social factors, and took another survey three years later. The researchers used British National Health Service records to track any deaths of participants, and the cause of death, over an average of 12 years from the time the women first joined the study.

At the start of the study, 20% of the study participants were smokers, 28% were ex-smokers, and 52% never had smoked. The researchers found that those women who were still smokers when surveyed three years later were nearly three times as likely as non-smokers to die over the next nine years.

The researchers also showed that risks among smokers increased steeply with the amount smoked. Even for light smokers having between one and nine cigarettes a day, death rates were double those for non-smokers.

The study appeared Oct. 27 on the website of The Lancet. The study abstract is available at


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