How long does quitting smoking extend life?

Longtime smokers can expect to lose about a decade of life, finds a study in the journal BMJ. The smoking-impact study was part of a larger project, called the Life Span Study, which follows the health of more than 120,000 Japanese men and women who joined the study starting in 1950.

From 1963 to 1992, health researchers collected information on the smoking habits of about 27,000 men and 41,000 women. The data (from surveys and office visits to doctors) included details of when the people started smoking and how much they smoked. The investigators tracked the causes of death in the group until 2008. Smokers who picked up the habit early in adulthood and did not quit ultimately lost a decade of life due to a variety of causes. However, those who quit by age 35 eliminated nearly all of the risk they would have faced if they continued to smoke.