Researchers found even older adults who quit smoking saw significant life expectancy benefits. Those who quit at age 65 gained an average of 1.7 years compared to those who continued smoking, while individuals who quit at age 75 gained 0.7 years on average.
The study, published in the American Journal of Preventive Medicine, used mortality data from multiple sources, including the Cancer Prevention Study II, 2018 National Health Interview Survey (NHIS) smoking prevalence data, 2018 U.S. population census data, and 2018 U.S. mortality rates to calculate relative risks (RRs) of all-cause mortality by smoking status. Life expectancies for never smokers, current smokers, and former smokers who quit at various ages between 35 and 75 years were calculated.
The researchers found current smokers aged 35, 45, 55, 65, and 75 who continued smoking lost an average of 9.1, 8.3, 7.3, 5.9, and 4.4 years of life, respectively, compared to never smokers. Individuals who quit at ages 35, 45, 55, 65, and 75 avoided an average life loss of 8.0, 5.6, 3.4, 1.7, and 0.7 years, respectively, compared to those who continued smoking. The probability of gaining at least one year of life for individuals who quit at age 65 and 75 was 23.4% and 14.2%, respectively.
The researchers employed Monte Carlo simulations with 10 million individuals at each age of quitting to calculate the probability distributions of years gained or lost by quitting smoking at various ages. Life expectancy for the general population at ages 35, 45, 55, 65, and 75 was 45.4, 36.2, 27.4, 19.5, and 12.3 years, respectively. Never smokers at these ages had life expectancies of 47.8, 38.4, 29.3, 20.9, and 13.4 years, respectively. Current smokers who did not quit had life expectancies of 38.7, 30.0, 22.0, 15.1, and 9.0 years, respectively. Former smokers who quit at each respective age had life expectancies of 46.7, 35.6, 25.4, 16.8, and 9.7 years.
The probability distributions of years gained by quitting revealed that 52.8% of 35-year-olds who quit at 35 gained at least one year of life expectancy, and 36.0% gained at least eight years. Among 55-year-olds who quit, 26.8% gained four or more years, while 23.4% of those who quit at age 65 gained at least one year.
The study’s findings closely aligned with previous research by Taylor et al, but produced lower estimates than those reported by Jha et al. The current study's inclusion of seniors aged 65 and older represents an important expansion, offering new insights into the benefits of quitting smoking at older ages.
The researchers noted that smoking intensity was not directly considered in the model. They also acknowledged use of 2018 data, which might slightly overestimate the harm from smoking but believed this was balanced by using older data, which could underestimate risks.
The research was funded by the National Cancer Institute and the FDA Center for Tobacco Products (Award Number U54CA229974).
The authors declared having no competing interests.