Patients who have previously been diagnosed with a chronic respiratory disease, like bronchitis, are at an increased risk for lung cancer, according to a large study analysis conducted by the American Thoracic Society.

"Associations between various respiratory diseases and lung cancer have been shown in earlier studies, but few of these studies considered multiple respiratory diseases simultaneously," Dr. Ann Olsson, study author of the International Agency for Research in Cancer in Lyon, France, said in a press release. Olsson and her team analyzed seven case-control studies involving more than 25,000 patients. This means researchers compared patients who were diagnosed with a respiratory disease (case) and patients who were not (control).

The results showed, in addition to chronic bronchitis, emphysema and pneumonia were associated with a greater increased lung cancer risk among subjects. Even when researchers adjusted their analysis for other respiratory diseases and smoking, lung cancer risk was still prevalent.

"The variations in the associations between lung cancer and different patterns of previous respiratory diseases that we observed in our study may indicate differences in the underlying etiological mechanisms," Olsson said. "Better understanding of these associations may help guide the type and frequency of clinical surveillance needed for patients with each of these diseases."

Chronic Obstructive Pulmonary Disease (COPD) is the official term for these respiratory diseases. According to the American Lung Association (ALA), COPD is the third leading cause of death in America, with up to 12.7 million adults in the United States suffering from a disease in 2011.

The ALA says smoking is the number one risk factor for COPD, followed by exposure to air pollution, secondhand smoke, occupational dusts and chemicals, in addition to a family history of respiratory infections.

A separate study published in The Lancet adds alcohol misuse, increased sodium intake, high blood pressure, high blood sugar, and obesity to the risk list. And researchers concluded reducing just six of the total risks for COPD will prevent 37 million premature deaths over the next 15 years.

Early detection of COPD is key to being successfully treated, the ALA says. Preventing COPD, in turn, prevents lung cancer. So anyone experiencing COPD symptoms should consult their doctor. Don't forget to mention a family history if one exists. It's how doctors can narrow down the treatment that will work for you.