Smokers who quit when they are young adults can live almost as long as people who never smoked, groundbreaking new research has found.
Smoking cuts at least 10 years off a person's lifespan. But a comprehensive analysis of health and death records in the United States found that people who quit smoking before they turn 40 regain almost all of those lost years.
"Quitting smoking before age 40, and preferably well before 40, gives back almost all of the decade of lost life from continued smoking," said Dr. Prabhat Jha, head of the Centre for Global Health Research at St. Michael's Hospital and a professor in the Dalla Lana School of Public Health at the University of Toronto.
"That's not to say, however, that it is safe to smoke until you are 40 and then stop," said Dr. Jha. "Former smokers still have a greater risk of dying sooner than people who never smoked. But the risk is small compared to the huge risk for those who continue to smoke."
His findings were published today in the New England Journal of Medicine.
Dr. Jha's team found that people who quit smoking between ages 35 and 44 gained about nine years and those who quit between ages 45-54 and 55-64 gained six and four years of life, respectively.
The study is unique as it examines the risks of smoking and the benefits of stopping among a representative sample of Americans. Earlier studies had examined specific groups such as nurses or volunteers who are healthier than average Americans overall. Importantly, the study is among the first to document the generation of women who started smoking when they were young and kept smoking through their adult lives.
"Women who smoke like men, die like men," Dr. Jha said. For women, the risks of dying from smoking-related causes are 50 per cent greater than found in the studies conducted in the 1980s.
Women and men who smoke both lost a decade of life. Current male or female smokers ages 25-79 had a mortality rate three times higher than people who had never smoked. Never smokers were about twice more likely to live to age 80 than were smokers.
This study adds to recent evidence from Britain, Japan and the United States that smoking risks involve about a decade of life lost worldwide. This includes a review of 50 years of smoking mortality in the United States published in the same issue of the New England Journal of Medicine and led by Dr. Michael J. Thun and other researchers from the American Cancer Society.
While about 40 million Americans and 4 million Canadians smoke, most of the world's estimated 1.3 billion smokers live in low- and middle-income countries. Worldwide about 30 million young adults begin smoking each year (about half of all young men and 10 per cent of young women) and most do not stop.
In many high-income countries more than half of people who ever smoked have quit, cessation remains uncommon in most low- and middle-income people. On current trends, smoking will kill about 1 billion people in the 21st century as opposed to 'only' 100 million in the 20th century.