Analysis of the Framingham Heart Study found that while quitting smoking lowers a person's CVD risk, that risk may not return to normal for up to 25 years.
A recent study is shedding new light on the impact of quitting smoking has over time in regard to a person’s risk of cardiovascular disease (CVD).
The study, performed by investigators at Vanderbilt University, found that while a patient’s risk of CVD was reduced by 39% within five years of quitting it can take up to 25 years after quitting for CVD risk to return to the level of a similar person who never smoked.
“Previous studies have shown the association between quitting and reduced CVD risk,” said lead investigator Meredith Duncan, MA, of the division of cardiovascular medicine at the Vanderbilt University Medical Center. “But the current Atherosclerotic CVD Risk Calculator, which is routinely used in clinical practice, considers former smokers’ risk to be similar to that of never smokers after five years of cessation, which is not consistent with these findings.”
To better understand the impact of smoking cessation over time, investigators performed a retrospective analysis using data from the Framingham Heart Study. A total of 8770 participants were included in the current analysis — participants were excluded if they had prevalent CVD, uncertain smoking history, or missing information on pack-years.
The mean age of the cohort was 42.2 years, 56% if the group was female, median BMI was 24.8 and 65% had a high school education or greater. Investigators noted that 2% and 27% of the cohort had baseline diabetes and hypertension, respectively. Additionally, 40% of the cohort had never smoked but 78% had consumed alcohol within the past year.
Of the 5308 participants identified as smokers, the median baseline pack-years of the group was 17.2. Investigators identified 2371 participants in this group as heavy ever smokers.
Over the 26.4-year follow-up period, a total of 2435 first CVD events were identified. Compared with current smoking, investigators pointed out quoting within 5 years was associated with significantly lower rates of incident CVD (incidence rates per 1000 person-years: current smoking, 11.56 [95% CI, 10.30-12.98]; quitting within 5 years, 6.94 ((95% CI, 5.61-8.59); difference, −4.51 (95% CI, −5.90 to −2.77)) and lower risk of incident CVD. (HR, 0.61; 95% CI, 0.49-0.76).
Conversely, when compared with never smoking, investigators noted that smoking cessation was no longer significantly associated with a greater CVD risk between 10 and 15 years after quitting (never smoking, 5.09 (95% CI, 4.52-5.74); quitting within 10 to more than 15 years, 6.31 (95% CI, 4.93-8.09); difference, 1.27 (95% CI, −0.10 to 3.05); hazard ratio, 1.25 (95% CI, 0.98-1.60).
In an editor’s note published accompanying the article, Thomas Cole, MD, MPH, associate editor of JAMA, described the implications of the study as “sobering” as cardiologists and physicians look to the future.
“On a population level, the implications of this study are sobering: reductions in CVD associated with declining smoking rates in countries such as Japan and the United States can be expected to lag quit rates by 10 to 15 years, and in countries where smoking rates appear to be increasing, such as China and Indonesia, rates of CVD are likely to increase for decades into the future,” Cole wrote.
This study, “Association of Smoking Cessation With Subsequent Risk of Cardiovascular Disease,” was published online in JAMA.