Former Smokers Who Kick the Habit See Survival Benefits Grow With Time

For smokers who quit, the survival benefits continue to grow as decades pass, such that the excess risk of cardiovascular death disappears after 20 years without smoking, suggests a research letter published in JAMA Internal Medicine.

Investigators found the risks of cancer and respiratory death also decrease but remain slightly elevated even three decades after cessation.

Lead author Blake Thomson, DPhil (American Cancer Society, Atlanta, GA, and Stanford University, Stanford, CA), said this study comes on the heels of others they’ve done looking at two factors: the age at which people quit smoking and the length of time since they stopped. “We think hopefully both are motivating,” he said. From a patient’s perspective, the questions are: “If you’re 40 years old, 50 years old, ‘What can I expect today if I quit?’ And then of course, whatever age you are, ‘If I quit today, in 10 years, in 20 years, what can I expect?’”

Here, the unique angle is cause-specific mortality, Thomson noted, but the takeaway is the same: “Quitting is extremely beneficial.”

For clinicians, however, it’s important to remember that prior smoking habits can remain relevant even after someone stops, he stressed. “People who quit do still have excess risk for several decades after they’ve quit. . . . They really do need to be managed a little more aggressively.”

As to why cardiovascular-related deaths reached the level seen by never smokers, while cancer and respiratory deaths did not, Thomson said the answer likely relates the biology behind how the various diseases develop. “But obviously, these are complicated issues. . . . There are so many types of cancer: it’s a very broad category,” and while chronic obstructive pulmonary disease predominates in the respiratory category, there’s still a range of etiologies, he explained. “It’s similar with cardiovascular disease,” which encompasses not only heart conditions but also things like stroke.

You should feel very comfortable believing that if you quit smoking today, you start accumulating benefits and those will continue to accrue over time. Blake Thomson

For their study, Thomson and senior author Farhad Islami, MD, PhD (American Cancer Society), analyzed data from the National Health Interview Survey for 438,015 adults (mean age 47 years; 56% female; 62% white, 17.5% Hispanic, and 14.4% non-Hispanic Black) by their smoking status at the time of recruitment between the years 1997 and 2018. They linked these details to the National Death Index to track cause-specific mortality risks.

Over 5.0 million person-years of follow-up, there were 11,860 deaths due to cardiovascular causes, 10,935 due to cancer, and 2,060 due to respiratory causes.

Current smokers, as would be expected, had higher risks of CV (RR 2.30), cancer (RR 3.38), and respiratory mortality (RR 13.31) over the decades compared with never smokers.

Former smokers continued to have elevated death risks in the early years after quitting, but these abated with time. The difference between former and current smokers for cardiovascular death was no longer significant by 20 years. For both cancer and respiratory mortality, risks shrunk considerably but continued to be higher even at 30 years and beyond.

Death Risk for Former vs Never Smokers: RR (95% CI)

With three decades or more of cessation, former smokers avoided all of the excess cardiovascular death risk, 93% of cancer death risk, and 97% of the respiratory death risk.

“These findings emphasize that with sustained cessation, cause-specific mortality rates among former smokers may eventually approximate those of never smokers,” the researchers conclude.

As with any observational study, there’s the potential for confounders like interactions between smoking and other risk factors, Thomson acknowledged. And, as noted in the paper, some former smokers likely restarted smoking during follow-up, while some current smokers later quit.

Even so, “it’s pretty compelling,” said Thomson. “Especially when you look at the respiratory mortality rates, you can’t really imagine what else could possibly be going on first to cause such a high relative risk of smoking and second to see it drop off so dramatically.” This dose-response pattern helps get closer to showing causality, he added.

“You should feel very comfortable believing that if you quit smoking today, you start accumulating benefits and those will continue to accrue over time,” Thomson commented.