"It's never too late to quit smoking," say researchers behind a new study revealed this week. The team found that while quitting smoking may not reduce the damage done to arteries, it reduces the risk of heart attack and death to levels enjoyed by people who have never smoked.

James Min, an associate professor with New York Presbyterian Hospital and Weill Cornell Medical College in the US, and colleagues presented their findings at the European Society of Cardiology Congress 2013, which is taking place in Amsterdam this week.

Prof. Min says:

"Our results show that quitting smoking does not reduce the amount of disease smoking causes in the coronary arteries, but it does reduce the risk of heart attack and death to the levels of non-smokers."

He explains that we already know smoking is a risk factor for cardiovascular disease and that several studies have found quitting smoking can reduce people's risk for heart attack and death. But none has looked at the effect quitting smoking has on presence and severity of coronary artery disease.

Coronary artery disease (CAD) is the most common type of heart disease, which is the leading cause of death in the US. According to the Centers for Disease Control and Prevention (CDC), heart disease killed nearly 600,000 Americans in 2010.

CAD is a leading cause of heart attack and occurs when cholesterol deposits called plaque build up in the arteries that supply blood to the heart. The plaque build up causes the arteries to become narrow over time, a process known as atherosclerosis.

For some people, the first sign of CAD is a heart attack, which happens when plaque completely blocks an artery carrying blood to the heart or when a piece of plaque breaks off, blocking blood flow in a coronary artery.

Effects of quitting smoking

Prof. Min says they wanted to find out what effect quitting smoking might have on the risk of cardiovascular events, death and the severity of CAD.

For their investigation, they looked at data from the CONFIRM (Coronary CT Evaluation for Clinical Outcomes: An International Multicenter Study) registry.

CONFIRM has collected heart disease and associated risk data from over 13,300 patients in nine countries on three continents: Europe, North America and East Asia. The patients include over 2,800 current smokers, over 3,100 past smokers and over 7,300 never-smokers.

The heart disease data was collected using coronary computed tomographic angiography (CCTA), a non-invasive scan that enables direct visualization of the coronary arteries.

When they analyzed the data, the researchers found that:

  • Severely blocked arteries were more common in past and current smokers than never-smokers.
  • Current and past smokers had a 1.5-fold higher chance of severe narrowing (stenosis) in 1 and 2 major arteries of the heart, and a 2-fold higher chance of severe narrowing in all three major heart arteries.
  • After 2 years of follow-up, 2.1% of the patients had either had a heart attack or died.
  • Heart attacks and deaths were nearly 2-fold higher among current smokers than never-smokers.

The team also found that despite CAD being more common and more severe among past smokers, their rates of heart attacks and death were the same as those of never-smokers.

And these rates persisted even when matched against never-smokers of the same gender, similar age and risk factors for CAD.

Prof. Min says theirs is the first study to show that while the damage to arteries remains, the risk for heart attacks and death falls to that of non-smokers when smokers quit.

He says more work is planned to find out exactly why this should be the case, and there are still lots of unanswered questions:

"For example, will the severe blockages observed in patients who have quit smoking provoke adverse events after 2 years (the duration of the present study)?"

"Further, does the duration of smoking or the number of cigarettes smoked per day affect the severity of CAD or the prognosis related to quitting smoking?"

"It's never too late to quit smoking," he says, "This study clearly shows that stopping smoking lowers the risk of heart attacks and death to the level of never-smokers."

A study published earlier this year found that quitting smoking by the age of 40 restores life expectancy to near normal.