This is important to know not just from a statistical point of view but also to do patient counseling. For instance saying that "smoking is the most important preventable contributor to the leading causes of death and disability (1. Coronary artery disease, 2. Lung Cancer & 3. Stroke)"

Leading causes of death in the United States rank as follows
1. Coronary artery disease.
2. Lung Cancer - it is now the commonest cancer in both men and women (used to be breast cancer in women)
3. Stroke
4. Breast Cancer
5. Colon cancer

In Young adults: 20-40
1. MVA
2. Homicide
3. Suicide

Preterm birth complicates 11 percent of all pregnancies in the U.S. and remains the leading cause of infant morbidity and mortality.