The figure of 14 million smoking-attributable major medical conditions was much higher than the previous estimate of 12.7 million medical conditions in 2000.
The findings of the study, published in JAMA Internal Medicine, suggest that the disease burden of cigarette smoking in the US "remains immense," write the authors.
Cigarette smoking is acknowledged as the leading cause of preventable deaths in the US, with experts finding cigarette smoke capable of harming almost every organ and organ system within the body.
The Centers for Disease Control and Prevention (CDC) regularly publish their estimates of mortality attributable to smoking, along with its economic cost. However, the population disease burden tends to receive less focus, despite smoking's status as a leading cause for many major medical conditions.
In 2000, the CDC published estimates of smoking-attributable mortality and reported that 8.6 million individuals suffered from a total of 12.7 million medical conditions attributable to smoking.
"Most of these conditions were chronic bronchitis and emphysema, often classified as chronic obstructive pulmonary disease (COPD)," write the authors, "but these estimates and methods, to our knowledge, have not been subsequently updated or refined."
Concerned that previous estimates of the disease burden of smoking could have been underestimated due to the absence of several major medical conditions caused by smoking, a study was conducted in order to produce estimates for smoking-attributable mortality for 2009.
The study was led by Dr. Brian L. Rostron of the Center for Tobacco Products, US Food and Drug Administration (FDA), in Silver Spring, MD.
A high estimate but 'generally conservative'
For the study, the researchers utilized data from the National Health Interview Survey (NHIS) from 2006-2012 and the National Health and Nutrition Examination Survey (NHANES). Population estimates were taken from the US Census Bureau in 2009.
Using NHIS data, the authors assessed smoking prevalence, disease prevalence and disease relative risk estimates. They estimated that 6.9 million American adults had reported a total of 10.9 million smoking-attributable medical conditions.
COPD estimates were then taken from NHANES spirometry readings and self-reported data. The data acquired from the medical examination of surveyed adults were adjusted to account for underreporting of this particular condition.
Combining the data, the researchers estimated that adults in the US had developed approximately 14 million major medical conditions in 2009 as a result of smoking.
The authors believe that this figure is "generally conservative," due to the existence of other conditions and medical events that were not included in the analysis. One such condition is ovarian cancer, which has been identified by cancer researchers as a disease that can be caused by smoking.
The report is also unable to quantify the contribution of secondhand smoking to the overall total of smoking-attributable major medical conditions.
'More than 40 million smokers in the US'
In an accompanying editorial, Dr. Steven A. Schroeder, of the University of California, San Francisco, states that the findings of the study should serve to keep smoking prevention and cessation as "the most important clinical and public health priorities for the foreseeable future."
Dr. Schroeder writes that a drop in smoking prevalence should not lead to the study's findings being discounted:
"Does it make any difference that smoking is even riskier than previously assumed? Given that adult and youth prevalence rates are at modern lows, would not the current trends take care of the problem? Unfortunately, no. Although prevalence is declining, that decline is excruciatingly slow, and there are still more than 40 million smokers in the United States."
He also suggests that "a long lag time" exists between changes in the habits of the population and changes in the prevalence of medical conditions. "Thus," he writes, "a decade from now we can predict that overall smoking-related deaths and morbidity rates should also have declined."
So, despite the numbers of smoke-free homes doubling in the past 20 years and record low levels of teen cigarette smoking, with approximately 1 billion smokers worldwide there remains much to be done to bring down figures such as the one provided by Dr. Rostron and colleagues.