There are approximately 14 million major medical conditions that can be attributed to smoking, according to a recent study.

Smoking is the leading cause of preventable disease in the United States. Cigarette smoking harms nearly every organ and organ system in the body.

"The disease burden of cigarette smoking in the United States remains immense and updated estimates indicate that [chronic obstructive pulmonary disease] COPD may be substantially underreported in health survey data," researchers said.

For the study, the research team collected and analyzed data from the U.S. Census Bureau in 2009, National Health Interview Survey data from 2006 through 2012 and data from the National Health and Nutrition Examination Survey.

First, they used National Health Interview Survey data to estimate that 6.9 million American adults had a combined 10.9 million self-reported smoking-attributable medical conditions. Then, they used COPD prevalence estimates from the National Health and Nutrition Examination Survey of self-reported and spirometry (a test of lung function) data to estimate that adults had a combined 14 million smoking attributable-conditions in 2009.

The largest cause of smoking-attributable illness in the United States was still COPD (emphysema) with an estimated 7.5 million cases attributable to smoking, but this number is 70 percent higher than the estimated cases based on self-reported prevalence data.

The findings were recently published in JAMA Intern Med.