August 20, 2019
By Megan Brooks
NEW YORK (Reuters Health) - Long-term smokers who kick the habit will improve their cardiovascular health, but not immediately, according to a new study.
The study found that the risk for cardiovascular disease (CVD) declines substantially in the first five years after a smoker stops smoking but does not match the risk of a never smoker until 10 to 15 years have elapsed since cessation.
"We cannot overstate the benefit of quitting smoking, even among individuals who have smoked heavily and for a number of years - the cardiovascular system begins to recover quickly, with some physiologic changes happening within hours of smoking cessation. Full recovery may take several years," Meredith Duncan, a PhD student at Vanderbilt University in Nashville, Tennessee, and the first author of the new report, told Reuters Health by email.
To evaluate the association between years since quitting and new CVD, Duncan and colleagues analyzed data on 8,770 participants in the Framingham Heart Study, including 2,371 heavy smokers who smoked the equivalent of a pack of cigarettes daily for 20 years. Their mean age was 42 and 45% were men. None had CVD at baseline.
Over an average follow-up of 26 years, there were 2,435 first CVD events (heart attack, stroke, heart failure or CV death) with 1,095 occurring among heavy smokers.
In adjusted models, smoking cessation was associated with a rapid decline in CVD risk versus continued smoking, with the risk significantly lower within five years of cessation in the pooled cohort (hazard ratio, 0.61). The results were similar in sensitivity analyses adjusting for cumulative pack-years (HR, 0.62).
However, former heavy smoking was associated with higher CVD risk compared with never smoking until 10 to 15 years after cessation in the pooled cohort (HR, 1.25).
"Our results reaffirmed the immense benefit of quitting smoking: within 5 years of quitting, former heavy smokers in our sample had a 39% cardiovascular disease risk reduction compared to continuing smokers," Duncan told Reuters Health. "Second, when pooling data from the original and offspring cohorts of the Framingham Heart Study, we observed that former smokers' cardiovascular disease risk remained elevated for 10-15 years since quitting compared to never smokers."
Duncan also noted that the Atherosclerotic Cardiovascular Disease Risk Calculator currently considers former smokers quit more than 5 years to be at similar cardiovascular disease risk as never smokers, all else held constant.
"As current smoking rates decrease in the United States, the number of former smokers increases, and cardiovascular risk in former smokers may be underestimated by current risk calculators. We believe it would be premature to restructure risk calculators based on these findings alone, but hope that these results motivate future investigations into these questions," she commented.
In an editor's note, Dr. Thomas Cole, JAMA associate editor, says, "Studies have come to different conclusions about how long it takes for the excess risk associated with smoking to subside to the level of a never smoker, with estimates varying widely, from 2 to 20 years."
"The study by Duncan et al, which was based on repeated assessments of tobacco exposure, other risk factors, and CVD outcomes, provides estimates of cardiovascular risk among former smokers that are likely to be more precise and accurate than those of previous studies," Dr. Cole writes.
"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. To counter these trends, all countries, particularly those most vulnerable to tobacco marketing, should implement tobacco control strategies to prevent smoking initiation and motivate current smokers to quit," Dr. Cole writes.
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