Lifestyle factors you can easily change account for more than 90 percent of heart attack risk, a landmark study of about 30,000 people in 52 countries suggests. And making small, positive changes in your everyday habits can have a surprisingly big impact on your heart health—or even save your life. Here’s a look at six of the worst habits for your heart, and how to turn them around. Being Glued to the Tube Spending too much time parked in front of the TV can actually be fatal, according to a 2011 study published in Journal of the American College of Cardiology. The researchers found that people who devoted four or more hours a day to screen-based entertainment—mainly watching the tube--had double the risk of a major cardiac event resulting in hospitalization, death or both, compared to those who spent less than two hours daily on these activities. Another compelling reason to limit TV time: Those who spent the most time on leisure-time screen-based entertainment had a 48 percent higher risk of dying prematurely, even if they also exercised. Recent research also shows that too much sitting can be just as bad for your heart as smoking. The Warning Signs of Heart Attack Having a Negative Attitude While stress and depression have long been linked to higher heart disease risk, a new Harvard review of more than 200 earlier studies, published this month in Psychological Bulletin, highlights the benefits of turning that frown upside-down: An optimistic outlook may cut heart disease and stroke danger by 50 percent. And while you may think that happy people are just healthier, the researchers found that the association between an upbeat attitude and reduced cardiovascular risk held true even when they took the person’s age, weight, smoking status, and other risk factors into account. Research also shows that laughter literally does the heart good, by expanding the linings of blood vessels and boosting blood flow. A fun way to add more joy to your life—and defuse stress--is laughter yoga, an exercise program that combines self-triggered mirth with deep yogic breathing to draw oxygen deeper into the body. Top 10 Simple Ways to Leave Stress Behind Ignoring Snoring Frequent loud snoring can trumpet obstructive sleep apnea (OSA), a dangerous disorder that magnifies heart attack and stroke risk, if untreated. OSA (bouts of interrupted breathing during sleep) frequently goes undiagnosed because people don’t recognize the symptoms, which include waking at night for no apparent reason and unexplained daytime drowsiness. If you fit this profile, ask your doctor to order a sleep study. Because OSA, which affects 18 million Americans, is most common in people who are heavy, treatment typically involves weight loss and in some cases, continuously positive airway pressure (CPAP), a device that blows moist, heated air in your nose and mouth as you sleep.