Quitting smoking at any age will increase life expectancy, according to a new study. While quitting early will avoid most years otherwise lost due to smoking, even those who quit at ages 65 and above can "meaningfully" increase their life expectancy, the study authors write.

Quantifying the impact of smoking on life expectancy and the potential benefits of quitting smoking cessation is "crucial" for motivating people who smoke to quit, according to the authors. While previous studies have attempted to estimate these effects, they were conducted more than a decade ago and did not include people over 65 years old who smoke.

The researchers calculated the harmful effects of smoking and the life expectancy benefits of quitting using mortality relative risks derived from various 2018 data sources. They then constructed life expectancy tables by smoking status -- never, current, former.

Next, they compared life expectancies for the three smoking statuses among individuals who had quit smoking at various ages, ranging from 35 to 75. In addition, they generated probability distributions of years lost due to smoking and years gained by quitting smoking at different ages.

The researchers found that compared to people who never smoked, those who smoke currently, at ages 35, 45, 55, 65 or 75 years, and who have smoked throughout adulthood until that age, will lose, on average, 9.1, 8.3, 7.3, 5.9, and 4.4 years of life, respectively, if they continue to smoke for the rest of their lives.

However, if they quit smoking at each of these ages, they will avoid an average loss of 8.0, 5.6, 3.4, 1.7, and 0.7 years. The chances of gaining at least one year of life among those who quit at age 65 was 23.4%, and for those who quit at age 75, the chances were 14.2%.

"This cessation benefit is not limited to young- and middle-aged adults who smoke; this study demonstrates its applicability to seniors as well. These findings may be valuable for clinicians seeking scientific evidence to motivate their patients who smoke to quit," the authors wrote. 

To download the full study, published in the American Journal of Preventive Medicine, click here