Cholesterol is a fatty substance in your blood. It can build up inside your arteries and block the blood flow to your heart or brain. Your risk of heart disease goes up if you don’t have enough HDL cholesterol (“good” cholesterol that clears the bad cholesterol away). You’re also at risk if you have high levels of LDL (“bad”) cholesterol or triglycerides (another substance that can build up).

This is the most important risk factor you can change. Smoking damages your arteries. It reduces blood flow to your heart and brain. It greatly increases your risk of heart disease, stroke, lung disease, and cancer. If you keep smoking after a heart attack, you can double your risk of a second heart attack.

High blood pressure occurs when blood pushes too hard against artery walls as it passes through the arteries. This damages the artery lining. High blood pressure raises your risk of heart attack and especially stroke.

Stress, pent-up anger, and other negative emotions have been linked to heart disease. Over time, these emotions could raise your heart disease risk.

This is caused by a combination of certain risk factors. It puts you at extra high risk of heart disease, stroke, and diabetes. You have metabolic syndrome if you have three or more of the following: low HDL cholesterol; high triglycerides; high blood pressure; high blood sugar; extra weight around the waist.

Diabetes occurs when you have high levels of sugar (glucose) in your blood. This can damage arteries if not kept under control. Having diabetes also makes you more likely to have a silent heart attack—one without any symptoms.

Excess weight makes other risk factors, such as diabetes, more likely. Excess weight around the waist or stomach increases your heart disease risk the most.

When you’re not active, you’re more likely to develop diabetes, high blood pressure, abnormal cholesterol levels, and excess weight.