The American Lung Association released a study Thursday that found a link between smoking and cancer, but it was not definitive.
The study is the latest to link cigarette smoking to lung cancer, which has become a leading cause of death in the United States.
Researchers analyzed data from more than 10,000 lung cancer cases, including more than 5,000 in California and the nation’s largest state.
They concluded that smoking may be responsible for around 20% of lung cancer deaths in the state.
“The findings support the concept that tobacco smoking is a cause of lung disease and that it is the primary contributor to lung disease,” Dr. Richard A. Kranish, the lead author of the study and an assistant professor at the University of California, Davis School of Medicine, said in a statement.
“While tobacco smoking has been associated with increased risk for lung cancer for years, this is the first time we have shown that the smoking behavior itself is the cause of this increased risk.
Kranis findings were confirmed by another study released Thursday, which found that a cigarette smoker who had been smoking regularly for 20 years was 10 times more likely to develop lung cancer than someone who had never smoked. “
In general, the risk of developing lung cancer increases with increasing smoking frequency.”
Kranis findings were confirmed by another study released Thursday, which found that a cigarette smoker who had been smoking regularly for 20 years was 10 times more likely to develop lung cancer than someone who had never smoked.
The other study, published in the Journal of the American Medical Association, found that smokers who started smoking within five years of the start of their studies were three times more than those who started after the age of 25.
Krantish said the new study was not able to determine the exact cause of the lung cancer risk in smokers who quit smoking after 20 years of regular smoking, but the researchers said their analysis found that smoking was linked to the development of lung tumors in those who stopped smoking at least five years after starting.
“What we know is that smoking increases the risk for developing lung tumors,” he said.
“We’re not saying it causes them, but we’re not going to say it’s the cause either.”
The findings were based on a large study of more than 8,500 people from California.
The researchers said they wanted to see if the association between lung cancer and smoking was more pronounced in smokers younger than 25, but did not find evidence to support this finding.
The authors said they did not have any data to link smoking to a specific type of cancer, only to a link to increased risk of lung cancers.
The American Cancer Society said in its statement that it was concerned about the findings.
“This is the biggest study ever conducted on lung cancer in adults and will help us better understand the risk factors and preventative measures that can reduce lung cancer risks,” said Dr. Robert J. Friedlander, president and CEO of the A.C.S., in a press release.
“Lung cancer is one of the leading causes of death worldwide and smoking has become the leading cause for smoking-related death, costing the lives of thousands of Americans each year.
We are concerned about how this study was done, how the findings are extrapolated and whether the results are reliable or not.”
In a statement, the American Lung Associations National Institute on Drug Abuse said it was working with the researchers to find the most effective way to prevent lung cancer.
“As a nation, we have seen a rise in lung cancer since the 1970s and the burden of this disease is rising,” said A.J. Laughlin, the executive director of the association.
“Today’s research is important to us and to help us understand how to prevent it from spreading.
We will continue to work to prevent the spread of this deadly disease.”
The American Academy of Family Physicians said it supports the findings of the research, but said it would be premature to make any definitive recommendations about the best way to discourage smoking.
“Smoking is associated with a range of cancers, including lung cancer,” said Ann Burdett, a spokeswoman for the group.
“If we do not act now, smoking will become a major killer of young adults.”
The association said it wants to make sure tobacco companies do not target smokers who have been exposed to asbestos or other harmful chemicals, but that some companies have tried to limit access to their products by making it harder to get an early warning about potential problems.
“It’s important that we get the message out that smoking is dangerous,” Burdets said.
The Associated Press writer Elizabeth Slattery contributed to this report.