3. Chronic lung diseases
> Total Deaths in 2013: 149,205

While cancer and heart disease death rates have decreased since 1999, the incidence of death attributable to chronic lung diseases has increased over the same time period. There were roughly 47.2 deaths for every 100,000 people due to chronic lung diseases in 2013, slightly more than the 44.5 deaths for every 100,000 people in 1999. The main contributors to this category of disease are emphysema and other chronic lower respiratory diseases. Smoking and secondhand smoke exposure, air pollution, toxin exposure, and obesity are all significant risks for chronic lung disease.

2. Cancer
> Total Deaths in 2013: 584,881

Cancer was the underlying cause of more than half a million deaths in 2013 — despite improving treatment and earlier detection methods. Such improvements certainly helped lower the incidence of cancer death during the last 15 years, from 197 to 185 deaths per 100,000 people. However, as the U.S. population ages, the total number of new cancer cases is expected to increase as age is the most important risk factor associated with cancer. According to the American Society of Clinical Oncology, cancer will overtake heart disease as the leading cause of death in the United States by 2030. While aging is unavoidable, there are multiple modifiable risk factors that can lower the risk of cancer; not smoking, minimal alcohol consumption, a healthy diet low in red and smoked meats, and avoiding radiation from the sun.

1. Heart disease
> Total Deaths in 2013: 611,105

The death rate from heart disease has decreased from 259.9 to 193.3 deaths per 100,000 people over the last decade and a half. This decline is likely due to lower smoking rates and improved medications for some modifiable risk factors such as high cholesterol and blood pressure, Allen explained. Despite recent improvements, heart disease is the leading cause of death in the United States. Diet is also a major factor. According to the CDC, 90% of Americans consume more sodium than is recommended. Excess sodium consumption can increase the risk of high blood pressure, which can in turn lead to heart disease and stroke. Cardiovascular diseases and stroke cost the nation an estimated $273 billion annually.