It’s no secret that smoking tobacco products is the leading cause of preventable disease in the U.S., and a new study suggests that tobacco is linked to 14 million medical conditions.

Researchers analyzed National Health Interview Survey data from 2006 through 2012, and National Health and Nutrition Examination Survey data to determine the extent to which tobacco harms the body. They discovered that 6.9 million U.S. adults suffered a combined 10.9 million smoking-attributable medical conditions, and 14 million cases of chronic obstructive pulmonary disease (COPD) in 2009 were found to be linked to tobacco smoking.

The researchers also discovered that emphysema is still the leading cause of smoking-attributable illness in the U.S., which affects 7.5 million people. However, the prevalence of emphysema may actually be 70 percent higher than estimated following analysis of the self-reported information.

The burden that cigarette smoking has in the U.S. still remains significant, and current estimates of COPD may actually be underreported in health survey data.

COPD a progressive disease that makes it difficult to breathe. Cigarette smoking is the leading cause of the disease – most people who have COPD smoke or used to smoke.

Tobacco control has been among the most important health successes over the past few decades; yet much more still must be done, considering the fact that the number of smokers across the globe is now just shy of 1 billion people.

The findings of the study are published in the journal JAMA Internal Medicine.