Coronary heart disease (CHD) still causes more deaths in the United States than any other condition. Several things, such as high cholesterol level, high blood pressure, diabetes, smoking, and physical inactivity, may lead to CHD. We commonly call such things risk factors for CHD. We know that middle-aged people who have these risk factors are more likely to have CHD later in life than are middle-aged people who do not have these risk factors. Whether having the risk factors during young adulthood predicts later CHD has been less clear.