The link between smoking and heart disease is one of the best established facts in medicine. According to the CDC, smoking causes one in every four deaths from cardiovascular disease and raises the risk of coronary heart disease and stroke by two to four times. The good news is that the risk starts falling soon after you stop, and keeps falling for years.
This guide explains how smoking damages the heart, why cutting down is not enough, and what the long-term studies show about how fast the risk drops after quitting. For the methods that give you the best chance of stopping, see our guide on how to quit smoking.
In this guide
How smoking and heart disease are linked
Coronary heart disease happens when plaque, made of cholesterol and other substances, builds up in the arteries that supply the heart. As the arteries narrow, blood flow falls, and a clot on top of a plaque can block an artery completely. That is a heart attack.
The CDC lists several ways smoking speeds up this process. Smoking can:
- Damage the cells that line the blood vessels
- Increase the buildup of plaque
- Thicken and narrow the blood vessels
- Make blood stickier and more likely to clot
- Lower “good” HDL cholesterol
- Raise triglycerides, a type of fat in the blood
Carbon monoxide from cigarette smoke also reduces how much oxygen your blood can carry, and nicotine raises your heart rate and blood pressure each time you smoke. Together, these effects put the heart under more strain while narrowing the vessels that feed it.
How much smoking raises heart risk
Smoking does not affect only the heart. The CDC lists a range of cardiovascular diseases it increases the risk of:
| Condition | What it is |
|---|---|
| Coronary heart disease | Narrowed heart arteries, including heart attack and sudden cardiac death |
| Stroke | A blocked or burst blood vessel in the brain |
| Peripheral artery disease | Narrowed arteries, usually in the legs, causing pain when walking |
| Abdominal aortic aneurysm | A dangerous bulge in the body’s main artery |
| Atherosclerosis | The plaque buildup that drives all of the above |
The CDC estimates that smoking raises the risk of coronary heart disease by two to four times and the risk of stroke by two to four times compared with not smoking. It also notes that even people who smoke fewer than five cigarettes a day can show early signs of cardiovascular disease.
Why one cigarette a day is not safe
Many smokers try to cut down rather than stop, hoping that fewer cigarettes means proportionally less harm. For lung cancer, the risk does roughly follow the number of cigarettes. For smoking and heart disease, it does not.
A 2018 meta-analysis in the BMJ pooled 141 cohort studies to measure the risk of light smoking. If heart risk rose in a straight line with the number of cigarettes, one cigarette a day would carry about 5% of the extra risk of smoking 20 a day. The figures were far higher:
| Group | Share of the extra risk of a 20-a-day smoker carried by smoking one a day |
|---|---|
| Men, coronary heart disease | 46% |
| Women, coronary heart disease | 31% |
| Men, stroke | 41% |
| Women, stroke | 34% |
In other words, a man smoking one cigarette a day carries close to half the extra heart disease risk of a pack-a-day smoker. Among studies that adjusted for other risk factors, the figure for men rose to 53%. The authors concluded that no safe level of smoking exists for cardiovascular disease, and that smokers should aim to quit rather than cut down.
Cutting down can be a step towards stopping, but when it comes to smoking and heart disease, it leaves much of the risk in place.
Smoking and heart disease: how fast the risk falls
The benefits of quitting start quickly. Based on the 2020 US Surgeon General’s report on smoking cessation, the CDC summarises how cardiovascular risk falls after you stop:
| Time after quitting | What happens to your heart risk |
|---|---|
| 1 to 2 years | Risk of heart attack drops sharply |
| 3 to 6 years | The added risk of coronary heart disease drops by half |
| 5 to 10 years | Risk of stroke decreases |
| 15 years | Risk of coronary heart disease drops close to that of someone who has never smoked |
Quitting also improves HDL cholesterol, reduces inflammation and clotting, and slows the progress of atherosclerosis. Research suggests it may also lower the risk of atrial fibrillation, heart failure and sudden cardiac death.
These benefits apply whatever your age and however long or heavily you have smoked. People who already have coronary heart disease benefit too: quitting lowers the risk of another heart attack and of dying from heart disease. For a fuller picture of the body’s recovery, from the first hours onwards, see our quit smoking timeline.
Former heavy smokers: the longer tail
A 2019 study in JAMA used data from the Framingham Heart Study, which has followed thousands of people for decades, to look at what happens to heavy smokers after they quit. It included 8,770 people and focused on those with at least 20 pack-years of smoking (for example, a pack a day for 20 years).
- The drop is fast. Within five years of quitting, former heavy smokers had a 39% lower risk of cardiovascular disease than people who kept smoking.
- The tail is long. Compared with people who had never smoked, their extra risk took 10 to 15 years to fade to the point where it was no longer significant, and in one group it took 25 years.
The authors noted that standard heart risk calculators often treat former smokers as higher risk for only about five years, which may understate the risk for heavy smokers. If you smoked heavily in the past, tell your doctor, even if you quit years ago, so it can be factored into your heart risk assessment.
Secondhand smoke and heart disease
The connection between smoking and heart disease extends to people who do not smoke themselves. According to the CDC:
- Non-smokers who breathe secondhand smoke at home or at work raise their risk of heart disease by 25% to 30%.
- Secondhand smoke raises the risk of stroke by 20% to 30%.
- In the US, secondhand smoke causes nearly 34,000 deaths from coronary heart disease and more than 8,000 deaths from stroke each year among people who do not smoke.
- Even brief exposure can damage blood vessels and make blood stickier.
Quitting protects the people you live with as well as your own heart.
Protecting your heart after you quit smoking
Stopping smoking is the single biggest step, but it works best alongside the other main heart risk factors:
- Know your cholesterol. A standard lipid panel is a start, and an ApoB blood test counts the particles that drive plaque. If your numbers are high, there are proven ways to lower cholesterol naturally.
- Check your blood pressure. It often falls after quitting, but high blood pressure is common and has no symptoms.
- Manage weight gain. Some people gain weight after quitting. Regular activity and a sensible diet help, and studies show the heart benefits of stopping outweigh the effect of typical weight gain after quitting.
- Stay active. As breathing and circulation improve, exercise gets easier, which helps your heart further.
For a complete overview of how to look after your heart, read our heart health guide for men. If you are thinking of switching to e-cigarettes along the way, our review of vaping vs smoking explains why the benefit depends on stopping cigarettes completely.
Frequently asked questions
How does smoking cause heart disease?
Smoking damages the lining of blood vessels, speeds up plaque buildup, narrows the arteries, makes blood more likely to clot, lowers HDL cholesterol and raises triglycerides. Carbon monoxide and nicotine add strain by cutting oxygen supply and raising heart rate and blood pressure.
Is smoking a few cigarettes a day bad for your heart?
Yes. A BMJ meta-analysis of 141 studies found that men who smoked one cigarette a day had 46% of the extra heart disease risk of men who smoked 20 a day. There is no safe level of smoking for the heart.
How long after quitting smoking does heart disease risk go down?
Heart attack risk drops sharply within one to two years. The added risk of coronary heart disease halves within three to six years, and after about 15 years it is close to that of someone who never smoked. Former heavy smokers may take longer.
Can quitting smoking help if I already have heart disease?
Yes. Quitting lowers the risk of another heart attack and of dying from heart disease, even in people who already have coronary heart disease.
Does secondhand smoke cause heart disease?
Yes. The CDC reports that regular exposure to secondhand smoke at home or work raises a non-smoker’s risk of heart disease by 25% to 30%.
The bottom line
The evidence on smoking and heart disease is clear. Smoking damages blood vessels, speeds up plaque and makes clots more likely, and even one cigarette a day carries a large share of the risk. The encouraging part is how quickly the heart responds to quitting: heart attack risk falls sharply within a year or two, the added risk halves within a few years, and over the following decade or so it moves close to that of a non-smoker. Quitting completely, rather than cutting down, is the change that matters.
This article is for general information and is not medical advice. If you have chest pain, shortness of breath or other heart symptoms, seek medical help straight away. Talk to your doctor or a stop smoking service for support with quitting.
Sources
- CDC: Health Effects of Cigarettes, Cardiovascular Disease
- Hackshaw A et al. Low cigarette consumption and risk of coronary heart disease and stroke: meta-analysis of 141 cohort studies. BMJ, 2018
- Duncan MS et al. Association of Smoking Cessation With Subsequent Risk of Cardiovascular Disease. JAMA, 2019
- US Surgeon General: The Health Consequences of Smoking, 50 Years of Progress (2014)
- US Surgeon General: Smoking Cessation, key findings (2020)