Former heavy smokers continue to have an increased risk of cardiovascular disease (CVD) for 16 years after they quit, so quit now, say researchers at Vanderbilt University.

"Most importantly, our results confirm that there is an immense benefit to quitting smoking and that former smokers can reduce their CVD risk by 38 percent within 5 years of quitting compared to continuing smokers," investigation lead Meredith Duncan told IFLScience via email.

The group’s as-of-yet unpublished study drew data from the groundbreaking Framingham Heart Study – a long-term, ongoing study on cardiovascular health that was initiated in 1948 with just over 5,200 adult volunteers from Framingham, Massachusetts. By following these individuals for many years, the original researchers gained valuable insight into what lifestyle factors are associated with the development of cardiovascular disease (CVD).

Now common knowledge, the study was the first to link compromised heart function and strokes to smoking, cholesterol, and high blood pressure. In fact, the term ‘risk factor’ was coined by one of the early investigators. Later cohorts added to the study include more racially diverse subjects and the children and grandchildren of earlier participants.

For this particular study, the team analyzed health outcomes from 8,687 people followed for a median of 27 years – until the development of CVD, death, or the end of the year 2014. All subjects were free of CVD when they joined, and about half were smokers.

The results indicate that more than 70 percent of cardiovascular disease events such as heart attacks, heart failure, and strokes occurred in people who smoked at least one pack a day for 20 years – the heavy smoking subgroup that Duncan's group had hoped to examine closer.

The statistics were adjusted to account for age, sex, education level, hypertension, diabetes, BMI, total cholesterol, and alcohol consumption.

More study findings are set to be presented at the American Heart Association’s 2018 Scientific Sessions meeting. 

"We know that quitting smoking is beneficial, no matter how long or how much someone has smoked, so it’s never too late to quit," Duncan said, explaining her team's research goals. "But we felt that since previous estimates of the CVD risk in former smokers compared to current and never smokers were based on simulated data or data with fewer measurements of smoking status and/or intensity, there was a lack of information about what actually happens to people in the long-term based on estimates from rigorously collected data."

A groundbreaking study published in the New England Journal of Medicine in 2013 found that smokers who never quit can expect to lose about a decade in life expectancy, yet those who stop by age 40 gained back nine of those years. Those who stopped before 35 regained the full 10 years, whereas those who quit between 45 and 54 got back six years of life expectancy. Of course, these figures are merely statistical patterns, not hard-and-fast rules of nature, and the study does not measure how many years are spent with poor quality of life thanks to lingering smoking-related conditions. Nevertheless, there appears to be heartening evidence that young smokers can recover from the damage they’ve done to their bodies once they stop.