It has long been known that smoking cigarettes is an incredibly unhealthy habit, but the true extent of the damage caused by lighting up is still being established today.
A recent study conducted by Vanderbilt University found that it takes smokers' hearts upwards of 15 years to fully recover from the effects of cigarettes. This is triple the previous estimate, which suggested that those who smoke regularly could see their risk of heart disease and stroke return to a normal level in just five years.
The study's lead author, Meredith Duncan, recently spoke to the Daily Mail about the findings of her research, and explained why these figures should be worrying for anyone who is/recently was a smoker.

"For people who have smoked heavily over many years, there could be changes in the heart and lungs that don’t completely normalize," Duncan said.
After analysing data from 8,700 people spanning 50 years, Duncan's team found that "heavy smokers" (people who smoked the equivalent of a pack of cigarette every day for 20 years) accounted for 70 per cent of heart attacks out of the group. After five years of quitting, however, these people's risk of heart attacks dropped by 38 per cent when compared to those who had continued their habit.
However, it took almost a further 11 years of no smoking at all for former heavy smokers' cardiovascular disease risk to drop to the same level as individuals who have never smoked.
But Duncan wanted to assure people that quitting smoking does have proven health benefits almost immediately.

In just 20 minutes after finishing smoking a cigarette, a person's heart rate and blood pressure will drop back down to a normal level. 12 hours after that, the levels of carbon monoxide in their blood become undetectable. Within a week, their risk of a heart attack will already have fallen, as, according to Duncan, the heart and blood vessels "are no longer exposed to chemicals in cigarette smoke that make platelets more 'sticky' and cause unwanted blood clotting."
"So even for heavy smokers, we cannot overstate the benefits of quitting smoking," she said.
"What’s key to remember is that the actual risk of heart attack and other forms of cardiovascular disease goes down, and this is a main finding of our current study."
Unfortunately, there is still a significant risk of lung disease attached to smoking, and more research still needs to be conducted on the matter.

"We previously performed an analogous investigation using lung cancer as our outcome instead of [cardiovascular disease]," said Duncan. "We would like to revisit that topic, this time incorporating genetic data into our models to assess the interaction of genes and smoking habits on lung cancer risk."
Recent statistics show that around 87 per cent of lung cancer deaths are linked to smoking, and it is not yet clear how quitting affects a person's risk of developing the disease.
Needless to say, giving up smoking (or, indeed, abstaining from the habit in the first place) lowers the risk of a number of potentially fatal health conditions - and it's never too soon to quit.