August 20, 2019
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Former heavy smokers may have elevated CVD risk beyond 5 years after cessation

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Meredith S. Duncan

A new study confirms that heavy smokers have a significantly lower CVD risk within 5 years compared with current smokers. However, compared with individuals who never smoked, the risk for CVD remained significantly elevated beyond 5 years.

According to the data published in JAMA, using pooled data from the Framingham Heart Study, researchers reported that in a cohort of 8,770 individuals (mean age 42.2 years; 55% women; 60.5% ever smokers; 27% heavy smokers), within 5 years of quitting, smoking cessation was associated with a lower rate of incident CVD compared with current smokers: 6.94 per 1,000 person-years vs. 11.56 per 1,000 person-years (difference, −4.51) over a median follow-up of 26.4 years. Within 5 years of quitting, former smokers also demonstrated lowered risk for incident CVD compared with continuing smokers (HR = 0.61; 95% CI, 0.49-0.76).

However, compared with never-smokers, former smokers’ CVD risk remained significantly elevated 10 to 15 years after cessation: 6.31 per 1,000 person-years (95% CI, 3.93-8.09) among former smokers who reporting a cessation duration of 10 to < 15 years vs. 5.09 per 1,000 person-years (95% CI, 4.52-5.74) among never-smokers (difference, 1.27; HR = 1.25; [95% CI, .98-1.60]).

“Our results reaffirmed the benefit of quitting smoking: within 5 years of cessation, former heavy smokers displayed a 39% cardiovascular disease risk reduction compared to continuing smokers,” Meredith S. Duncan, MA, database administrator for the division of cardiovascular medicine at the Vanderbilt University Medical Center, told Cardiology Today. “When pooling data from the original and offspring cohorts of the Framingham Heart Study, we also observed that former smokers’ CVD risk remained elevated for 10 to 15 years since quitting compared to never smokers.”

This retrospective study focused on prospectively collected data from the Framingham Heart Study in the original cohort (n = 3,805) that attended their fourth examination in 1954 to 1958 and in the offspring cohort (n = 4,965) that attended their first examination in 1971 to 1975. Researchers used the data of participants without baseline CVD to evaluate the association of years since smoking cessation and incident CVD, defined as MI, stroke, HF or CV death. Smoking status and clinical characteristics, including BP, cholesterol levels and others, were updated regularly at every follow-up (every 2 years in the original cohort; every 4 years in the offspring cohort).

In this study, those who reported ever smoking had a median of 17.2 baseline pack-years. In total, there were 2,371 heavy ever-smokers (17% former; 83% current).

Over the median follow-up of 26.4 years, 2,435 first CVD events occurred. Of those, 1,612 occurred in the original cohort (664 among heavy smokers) and 823 in the offspring cohort (430 among heavy smokers).

“The Atherosclerotic CVD Risk Calculator is currently used by clinicians to help patients assess risk and guide lifestyle modifications for improved heart health; it considers former smokers quit more than 5 years to be at similar CVD risk as never smokers, all else held constant,” Duncan said. “With more smokers quitting their habit, the number of former smokers increases, and cardiovascular risk in former smokers may be underestimated by current risk calculators. It would be premature to restructure risk calculators based on these findings alone but we hope these results motivate future investigations into these questions, some of which we plan to undertake in the near future.”

Researchers stated that due to the limited sample size of the cohort of this study compared with previous analyses of CVD incidence and smoking cessation, these findings are only meaningful to ever-smokers with a cumulative history of more than 20 pack-years. Additionally, this study cohort consisted of primarily white individuals of European ancestry, which could also limit the generalizability of these findings for ever-smokers of various races and ethnicities.

“We cannot overstate the benefit of quitting smoking, even among individuals who have smoked heavily — the cardiovascular system begins to recover quickly, with some physiologic changes happening within hours of smoking cessation,” Duncan said. “Full recovery may take several years so today is a great day to quit smoking and make an appointment with a doctor to discuss other steps toward heart health.” – by Scott Buzby

For more information:

Meredith S. Duncan, MA, can be reached at meredith.s.duncan@vumc.edu.

Disclosures: Duncan reports no relevant financial disclosures. Senior author, Hilary Tindle, MD, MPH, provided input on design for a phase 3 trial of cytisine proposed by Achieve Life Sciences and also served as a primary investigator of NIH-sponsored studies for smoking cessation that include medications donated by the manufacturers.