US researchers said it takes at least five to 10 years after quitting smoking for cardiovascular disease (CVD) risk to become as low as that of a person who has never smoked.
In their study published in the Journal of the American Medical Association (JAMA), they said the risk of these diseases has significantly dropped among former smokers.
Led by Meredith Duncan from the Vanderbilt University Medical Center, the researchers used data from the Framingham Heart Study that started in 1984 to examine the risk of heart diseases among Framingham's residents.
The researchers analyzed data of the first generation of participants, along with the data of their children who partook in the study since 1971. The study involved a total of 8,770 participants, 2,370 of whom were heavy smokers or still smoke. According to the researchers, a heavy smoker is the person who smokes an average of 20 cigarettes a day over 20 years.
During an average follow-up of 26 years, more than 2,435 participants had a heart attack, stroke, heart failure or died from heart disease. The findings showed that former smokers' risk for heart events is lower than that of those who continue to smoke.
But it takes 10 to 15 years before the risk becomes similar to that of someone who never smoked.
The researchers said this period is longer than what was previously assumed by researchers.
"It was believed that the risk of developing CVD among former smokers drops to equal that of a non-smoker after five years," explained a cardiologist at the Hospital Linn der Weser, Bremen.
"The study clearly showed that quitting smoking is still feasible, even if you are a heavy smoker."
This applies, at least, to the risk of heart disease. Researchers did not consider other health consequences of smoking, such as lung disease or cancer.
The cardiologist from the Linn der Weser Hospital said the study findings on former smokers' heart health are important for doctors for several reasons, including therapeutic planning.
"We have been treating former smokers for five years after quitting. But the study now confirms that quitters should be followed-up for a longer period and classified in a more vulnerable group."
This is also confirmed by the authors of the study, who cautioned against underestimating the risk of heart and circulation diseases after quitting smoking, especially in countries such as the United States, where the number of quitters is increasing.
"The current study does not support the hypothesis that five years after quitting, former smokers are at the same risk as non-smokers, for heart disease and circulation."
Thomas Cole, a JAMA author, said the results of the study are modest, noting that the 10 to 15 years period for a lower CVD risk cannot apply to countries with low smoking rates.
In countries such as China and Indonesia, Cole predicted that heart and blood circulation diseases will increase in the long run because of the growing number of smokers in these countries.
Researchers from Australia recently found that smokers were nearly three times more likely to die of cardiovascular disease than people who had never smoked in their lives and that smokers were twice as likely as non-smokers to have a stroke or heart attack.
Their study was published in the journal BMC Medicine. But the good news is that those who stop smoking before the age of 45 can overcome 90 percent of the risk of heart and circulation disease caused by smoking.
