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In the United States, almost one-third of all deaths from coronary heart disease each year are related to smoking.¹ Researchers don't know exactly how smoking harms your heart, but they do know that nicotine and other chemicals in cigarette smoke damage the lining of your arteries. And these chemicals also make blood stickier and more likely to clot.

Blood clots in the arteries that take blood to your heart (your coronary arteries) can block your heart's blood supply and cause parts of your heart muscle to die.

If you've already been diagnosed with heart failure, smoking is particularly dangerous.

If you stop smoking, you can reduce your risk of getting heart disease or having a heart attack. Things that can help you give up include nicotine gum, a nicotine skin patch, drugs called bupropion (Zyban) and varenicline (Chantix) and counselling. To learn more, see our information on nicotine addiction.

Having diabetes increases your risk of getting heart failure. And if you get heart failure, you're more likely to need hospital treatment if you have diabetes.² There are two types of diabetes: type 1 and type 2. Both types increase the risk of heart problems.

Researchers think that diabetes changes the shape of the muscle that surrounds your heart. This makes it harder for your heart to work normally and increases your chances of getting heart failure.

Having diabetes means you have too much glucose in your blood. Glucose is a kind of sugar that your body uses as a source of energy. If it builds up in your bloodstream and it can make you sick. Diabetes doesn't go away. Untreated, it can lead to serious health problems. But if you make changes to your lifestyle, take medication and keep a close watch on your condition, you can keep your glucose levels under control. You should be able to live a long and healthy life.

Controlling your blood sugar level can reduce your risk of having a heart attack or dying from heart disease.³ How you do this will depend on which type of diabetes you have. If you have type 1 diabetes, you will need daily insulin shots and you will need to keep a careful watch on your glucose levels. If you have type 2 diabetes, you may need to take pills or have insulin shots. Whichever type you have, being more active and being careful about what you eat can help control your blood glucose levels.

To learn more, see our articles on diabetes.

Cholesterol is a fatty substance in your blood. There are two main types of cholesterol:

• "Bad" cholesterol (low-density lipoprotein cholesterol, or LDL)
• "Good" cholesterol (high-density lipoprotein cholesterol, or HDL).

If you have a lot of bad cholesterol in your blood, you have a higher risk of getting heart disease and having a heart attack. Having more good cholesterol lowers your risk of heart disease.

Your cholesterol level is affected by what you eat, how much you exercise and whether you smoke. It's also affected by your family history. If you have a high level of bad cholesterol, talk to your doctor about how you can lower it. To find out more, see our information on high cholesterol.

If you are overweight, you may also have too much "bad" cholesterol (LDL cholesterol) in your blood. This type of cholesterol can clog the blood vessels that take blood to your heart. Being overweight also increases your chances of having high blood pressure. And carrying too much weight makes your heart work harder. All these things are bad for your heart.

If you want to find out whether you are overweight, you can work out your body mass index (BMI). Your body mass index compares your height with your weight.

People with a BMI of 25 or more are overweight. People with a BMI of 30 or more are obese.⁴ If you are overweight or obese, you might want to talk with your doctor about how you can lose weight.

To learn more, see our articles on obesity.

There's good evidence that if you do some exercise on most days, you can reduce your chances of getting heart disease. People who don't exercise regularly are two or three times more likely to get heart disease.^{5 6}

You don't need to do strenuous exercise. Going for a long walk every few days can help. Or you could swim or ride a bike.

Drinking too much alcohol on a regular basis can damage your heart.¹

If your heart failure has been caused by drinking too much, stopping drinking can help your symptoms.²

This information is for educational use only, and is not a substitute for prompt professional medical advice. Readers should always consult a physician or other professional for advice and treatment. ©BMJ Publishing Group Limited 2008. All rights reserved.