People with cystic fibrosis are living longer than ever, but those in Canada live nearly 10 years longer than those in the United States, a new study finds.

Cystic fibrosis is a genetic disease that affects the lungs and digestive tract. It causes the production of a thick, sticky mucus that clogs the lungs. This may cause life-threatening lung infections. People with cystic fibrosis also have difficulty properly breaking down and absorbing nutrients from food, the researchers explained.

Between 2009 and 2013, the average Canadian with cystic fibrosis lived to just under 51 years. In the United States, someone with the lung disorder could expect to live an average of close to 41 years, the study found.

Why the difference?

Although the study didn't specifically look at the reasons behind the gap, possible reasons include diet, better access to lung transplants and universal health insurance, according to study lead author Dr. Anne Stephenson and her colleagues. Stephenson is a cystic fibrosis researcher at St. Michael's Hospital in Toronto.

The study authors noted that people with cystic fibrosis in Canada began eating a high-fat diet in the 1970s, something not implemented in the United States until the 1980s. Consuming more calories improves nutrition, which has been linked to improved survival in people with cystic fibrosis, the researchers said.

Normally, progressive lung disease is a common cause of death for cystic fibrosis patients, the researchers added.

But, people with cystic fibrosis in Canada are more likely to receive a lung transplant. A transplant is one of the few treatments that can have an almost immediate positive impact on survival, the study authors explained.

"Achieving a better understanding of the drivers behind differences in survival rates is critical to our mission to improve and extend the lives of people with cystic fibrosis," said lead study investigator Dr. Bruce Marshall. He is senior vice president of clinical affairs for the Cystic Fibrosis Foundation.

"As a result of this study, we will be conducting further research to better understand the role of nutrition and insurance status -- and are encouraged that the findings reinforce the central goal of our lung transplant initiative, a comprehensive effort to improve transplant outcomes for people with cystic fibrosis in the United States," he concluded in a St. Michael's Hospital news release.

The study included data from more than 45,000 people in the United States and nearly 6,000 people in Canada with cystic fibrosis. The study data stretched from 1990 to 2013.

After taking into account factors such as age and how sick a person was, the risk of death among patients was 34 percent lower in Canada than in the United States, the findings showed.

Canada has universal health care. When Canadians with cystic fibrosis were compared to people in the United States with the disease who had private health insurance, there was no survival difference, the study authors said.

But the risk of death for Canadians with the lung condition was 44 percent lower than for U.S. cystic fibrosis patients who had continuous Medicaid or Medicare coverage, 36 percent lower than for people with intermittent Medicaid or Medicare coverage, and 77 percent lower than for people without health insurance or unknown coverage status, the researchers reported.

The study was published March 14 in the journal Annals of Internal Medicine.