Causes of Diseases
Measures of associations remind us that diseases are not random events but results of the interplay between genes and environmental factors. We are therefore able to prevent a number of some diseases, or at least to delay their time of onset by reducing the causes that are reducible. If we could convince smokers to stop smoking, provide basic health care to all, make the inactive be more physically active, reduce air pollution, eliminate the most dangerous occupational exposures, encourage people on an unhealthy diet to eat more fruit and vegetables, and make the poor more wealthy, we could prolong life substantially for many people. If we only did this by taking away exposures that people like, many would feel life was prolonged even if it was not and that is not our aim. In public health and clinical medicine we try to add life to years as well as years to life.