It may take more than two decades about the risk of heart disease to return to the average level after the person stops to smokes, the new study shows.

It has been known for decades that cigarette smoking can cause significant damage to the heart. According to data from the World Health Organization (WHO), the World Heart Federation and Newcastle University in Australia as of 2020, every year 1,9 million people die of heart disease caused by smoking.

In the study, published in the journal JAMA, scientists from South Korea examined the health data of more than 100.000 ex-smokers and more than four million people who had never smoked. Ex-smokers were followed for 10 years after they quit smoking. Other details are also recorded, including age when they started smoking, how many cigarettes they smoked per day, and how old they were when they stopped smoking.

The study showed that the relationship between smoking and the risk of cardiovascular disease is dose dependent – meaning that for those who were "light" smokers, the risk dropped dramatically relatively quickly after quitting.

However, for "heavy" ex-smokers, who smoked for at least eight years, the researchers concluded that they may need 25 years on the risk of heart attack and stroke to decrease as in people who have never smoked.

"Heavy" ex-smokers should be said to have the same risk of cardiovascular disease as patients who continue to smoke, the authors of the study said.

Dozens of studies have shown that smoking is linked to heart failure – a condition in which the heart muscle does not pump blood around the body as well as it should, usually because it is too weak or stiff.

As a result, the heart cannot supply the organs and tissues with oxygen and vital nutrients needed for normal functioning. Seven thousand chemicals in tobacco -- including tar and others -- can damage the blood vessels that supply the heart, which is thought to be responsible for some of the damage that smoking causes to the heart. The Daily Mail.