When assessing your risk of having a heart attack, it's important to know there are factors you can control and others you can't.

Some, such as age, are fixed. But others related to diet and exercise, among other things, can be modified.

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In either case, it's important to know the elements that may contribute to a heart attack — which occurs when the arteries that carry oxygen and nutrients to the heart become blocked, severely limiting or cutting off blood supply.

Knowing and addressing these risk factors is crucial: Around 800,000 Americans experience a heart attack each year (roughly one every 40 seconds), according to the Centers for Disease Control and Prevention.

Deaths from heart attack help make up the more than 800,000 annual deaths tied to cardiovascular disease — which claims more lives than all forms of cancer combined.

Get to know these common heart attack culprits to keep your ticker in top shape.

Heart attack risk factors you cannot control:

Age. The majority of heart attack deaths occur in patients ages 65 and older, but a man's risk begins to increase at 45 (for women, it starts at 55).

Gender. Overall, men have a greater risk of heart attack, but women are more likely to experience subtler heart attack symptoms such as fatigue and nausea - not just chest pain.

Genes. Family history can dictate early trouble. See a doctor if your father or brother was 55 or younger when diagnosed with coronary heart disease (or 65 for your mother or sister).

Heart attack risk factors you can control:

Cholesterol. Healthy levels of LDL ("bad") and HDL ("good") cholesterol help prevent arterial plaque buildup. Lifestyle changes can steady the balance, but you may also need medication.

Diet. Healthful food is a highly effective weapon against heart disease. Focus on fruits, vegetable and grains - as well as low-fat dairy, poultry and fish. Limit red meat and sugar.

Drinking. Alcohol can amplify cardiac health risks, raise triglycerides and cause irregular heartbeat. Consume safely by having no more than two drinks per day for men (and one for women). 

Blood Pressure. High blood pressure forces the heart to work harder, causing damage over time. If your blood pressure is higher than 120/80, your heart attack risk is considered elevated.

Diabetes. Patients with diabetes have twice the risk of coronary heart disease. That's because high blood sugar, if uncontrolled, can lead to increased plaque in your arteries. 

Smoking. Smoking is directly related to one in four heart attacks. People who smoke have a heart attack risk two to three times higher than nonsmokers. 

Physical Activity. Exercise can lower blood pressure, cholesterol and weight. Be active every day - with three to four 40 minute sessions of moderate to vigorous activity each week.

Weight. Being overweight or obese is linked to several related heart attack risk factors. Your doctor can help you determine an ideal goal weight based on height and age.

Emotions. Chronic stress and anxiety can take a tool. They may cause arteries to tighten, raising blood pressure. Poor mental health might also prompt inactivity and a bad diet.

Sources: American Heart Association, Centers for Disease Control and Prevention, National Heart, Lung and Blood Institute, University of Michigan Frankel Cardiovascular Center