It's never too late to reap the benefits of a smoke-free life.

No matter at what age a person quits smoking cigarettes, they are likely to add years to their life expectancy, according to a large new analysis from researchers in Canada and Norway.

"Quitting smoking is ridiculously effective in reducing the risk of death, and people can reap those rewards remarkably quickly," says public health scientist Prabhat Jha from the Center for Global Health Research at Unity Health Toronto.

If a smoker can stay away from the highly addictive habit for up to a decade, Jha and colleagues say they can hope to live nearly as long as someone who has never picked up a cigarette in their life.

The authors of the study go on to explain that if a person of any age stops smoking for fewer than three years, they can potentially avert 5 years of life lost. If a person can stop smoking for a decade, they can potentially avert a decade of life lost.

The younger a smoker decides to make that change, the better the gains to their life expectancy overall.

The promising results come from observational studies in Norway, the UK, the US, and Canada. For 15 years, scientists tracked the health of nearly 1.5 million adults living in these high-income nations. Researchers at the Center for Global Health Research in Canada and UiT – The Arctic University of Norway have now analyzed that data with respect to the risks of smoking.

Smokers in the study, who were over the age of 40 and under the age of 80, lost on average about 12 to 13 years from their lives compared to never-smokers. People who managed to quit smoking for ten years, however, seemed to nearly reverse the all-cause fatality risks associated with their old habit.

The risk of death from diseases directly related to smoking, like stroke, cardiac arrest, or cancer, were also significantly alleviated.

"Many people think it's too late to quit smoking, especially in middle age," says Jha.

"But these results counter that line of thought. It's never too late, the impact is fast and you can reduce risk across major diseases, meaning a longer and better quality of life."

Smoking Life Expectancy
Life expectancy differences between former smokers, current smokers, and never smokers, translated into years and divided by gender. (Rin Cho, NEJM Evidence, 2024)

The current findings are supported by previous observational studies, in which the benefits of quitting smoking were associated with significant improvements in life expectancy, sometimes adding up to ten years in total.

Jha and colleagues settled on similar numbers using a large cohort.

Their results do not mean that the consequences of smoking are wholly reversible. In the analysis, the risk of death from lung conditions was not as significantly reduced among former smokers as other health conditions, "reflecting long-term irreversible airway damage", the researchers say.

Nevertheless, quitting smoking is still the best available option to improve lung health and function among smokers.

If a person over 40 stops smoking for ten years, for instance, they can potentially avert 8 years of life lost due to cancer, the findings suggest. This means they are only four years 'behind' a never-smoker in that risk category.

Some prior data has found that after a decade of no smoking, the risk of lung cancer will be half that of a non-smoker of similar age. After two decades, the risk of heart attack or stroke could be on par with a person who has never smoked.

The current findings suggest such benefits could be realized even sooner.

"Helping smokers quit is one of most effective ways to substantially improve health," says Jha.

"This can be done with concern, and without judgment or stigma, recognizing that cigarettes are engineered to be highly addictive."

The study was published in NEJM Evidence.