Just 12 hours after you quit smoking, the amount of carbon monoxide in your blood decreases, which increases the amount of oxygen in your blood – giving your heart a well-deserved break. A year after you quit, your likelihood of a heart attack and risk of heart disease drops to half that of a smoker's risk. The benefits keep coming over time: 15 years after quitting smoking, your risk of heart disease finally drops to the levels of that of a nonsmoker, and your risk of other cardiac issues, like arrhythmia and angina, drop to normal levels, too.
However, that doesn't mean you can live as if you never smoked just because you kicked the habit, especially if you were an avid smoker before. Your heart health was damaged the moment you picked up that cigarette. Cardiologist John Higgins explained to Everyday Health, "If you light up and smoke now, the substances in the cigarette are going to increases your heart rate and blood pressure right away. Long term, you're looking at hypertension, which, coupled with the fact that smokers often don't work out and are overweight, adds to the negative heart effects."