The Surgeon General’s Report of 1964, which outlined, for the first time, the effects of smoking on health, along with the tobacco control efforts that followed, are responsible for adding nearly 20 years of life to eight million people, according to a study published in the Journal of the American Medical Association.

The study was conducted by a group of researchers from the Cancer Intervention and Surveillance Modeling Network (CISNET), and was funded by the National Cancer Institute.

The research team examined smoking patterns up through 1964 and then modeled mortality rates based on what would likely have happened in the absence of tobacco control. They then compared actual death rates. This resulted in an estimated 157 million years of life saved—19.6 additional years for each smoker who quit, according to the study.

“The report and subsequent tobacco control efforts represent the most dramatic and successful public health campaign in modern history, in terms of benefit to the entire population,” says, David T. Levy, PhD, a population scientist at Georgetown Lombardi Comprehensive Cancer Center and the study’s senior author.

“In 1964, more than 40 percent of American adults smoked, and now, 50 years later, less than 20 percent use cigarettes. Our research suggests that this dramatic reduction is due to the 1964 Surgeon General’s report and the tobacco control activity that followed, ” he adds. “While this is a significant public health achievement, we have much more to do—smoking continues to be the leading contributor to the nation’s death toll.”