Three common respiratory diseases seem to be associated with an increased risk of lung cancer, researchers report.
The investigators analyzed data from seven studies that included more than 25,000 people and found that chronic bronchitis, emphysema and pneumonia were linked with a greater risk of developing lung cancer.
Having asthma or tuberculosis was not associated with a higher lung cancer risk, according to the study published in the Aug. 15 issue of the American Journal of Respiratory and Critical Care Medicine.
People who had all three -- chronic bronchitis, emphysema and pneumonia -- had a higher risk of lung cancer than those with chronic bronchitis only. There was no increased risk of lung cancer among those who had chronic bronchitis along with asthma or tuberculosis, the study found.
In a journal news release, study author Ann Olsson said the reason respiratory illnesses may affect lung cancer risk in different ways could have to do with underlying disease mechanisms.
A better understanding of the links between respiratory ailments and lung cancer may help inform doctors on how best to monitor and help patients, said Olsson, of the International Agency for Research in Cancer in Lyon, France.
Although the study found an association between certain respiratory diseases and lung cancer risk, it did not prove a cause-and-effect relationship.