The World Health Organization observes the World No Tobacco Day on May 31 to highlight the health and other risks associated with tobacco use.

The focus of World No Tobacco Day 2018 is "Tobacco and heart disease” in order to raise awareness about the proven link between tobacco and heart and other cardiovascular diseases (CVD) and measures the government and the public can take in order to reduce the risks to heart health posed by tobacco.

After you quit smoking, you can feel some of the effects immediately, while the long-term effects occur over time. Here’s a look at the timeline of health improvements someone who has quit smoking would experience.

Short-term effects

The heart rate starts to return to normal after you have not smoked a cigarette for 20 minutes. This is because tobacco contains chemicals that speed up the heart and also raises the blood pressure, according to CDC.

After two hours of not having smoked, you will feel warmth return to your fingertips and other extremities. This means your blood pressure has normalized and your peripheral circulation has begun to improve. However, this is the same time some of the withdrawal symptoms of quitting smoking show up such as anxiety, increased appetite, irritability, sleeplessness, and intense cravings.

It takes at around eight hours for nicotine and carbon monoxide levels in the blood to reduce by more than half and oxygen levels return to normal, according to National Health Service. Carbon monoxide, which enters the body from a lit cigarette, prevents blood from bonding with oxygen. The lack of oxygenated blood can lead to serious cardiovascular complications.

World No Tobacco Day
This photo shows students wearing masks with no smoking signs to support World No Tobacco Day at a primary school in Handan, northern China's Hebei province, May 30, 2016. Getty Images/ STR

A chain-smoker often finds that his or her sense of smell and taste is not at its full capacity. This is because these senses depend on your nerve-endings which are deadened when you smoke. It takes 48 hours after you quit smoking for the senses to normalize and gain back their original capacity. Also, lungs start to clear out mucus and other smoking debris around this time.

After 72 hours, the body is rid of the piled up nicotine inside and hence, the bronchial tubes begin to relax and energy levels increase. However, along with it, advanced tobacco withdrawal symptoms like increased tension, cravings, irritability show up among other behavioral issues.

Long-term effects

The body starts various regenerative processes after you have not smoked for two to three weeks. According to the American Heart Association, the lung capacity begins to improve, along with one’s blood circulation, allowing one to perform intense activities such as exercising, running, and various other physical activities that rely on endurance and stamina.

After one to nine months of saying “no” to smoking, the body starts rebuilding cilia, which are damaged due to smoking. Cilia are small hair-like organelles which help in reducing your risk of infections by pushing mucus out of your lungs. As a result, lung function increases by up to 10 percent and coughs, wheezing and breathing problems improve.

If you have managed to stay away from smoking for a year, you would have successfully decreased the risk of coronary heart disease by half of that of a smoker’s.

After five to 15 years after quitting smoking, the chance of stroke decreases to match that of an average non-smoker because carbon monoxide no longer constricts the blood vessels, hence reducing an ex-smoker’s mortality rate. Also risk of lung cancer falls to half that of a smoker.