People with cystic fibrosis (CF) who live in Canada can statistically anticipate living about 10 years longer than CF patients with similar demographics and disease profiles living in the U.S., according to new research.
The study, “Survival Comparison of Patients With Cystic Fibrosis in Canada and the United States: A Population-Based Cohort Study,” was published March 14 in the journal Annals of Internal Medicine.
“In 2011, the median age of survival of patients with cystic fibrosis reported in the United States was 36.8 years, compared with 48.5 years in Canada,” the study reported.
In data from the last five years of the study, 2009 to 2013, the gap between the two countries was shorter and the median age of survival was longer — 50.9 years for CF patients in Canada compared to 40.6 years in the U.S., Dr. Anne Stephenson, a respirologist and CF researcher at St. Michael’s Hospital in Toronto, said in a press release. Stephenson was also the lead author of the study.
The authors caution that direct comparisons of lifespan estimates between national CF registries is a challenge due to inherent differences in the methods applied and different data-processing techniques. And they note that the life expectancy for people with CF is generally increasing.
However, the gap between the two countries’ respective CF survival expectancies began to widen in 1995 and accelerated in 2005. Even after taking into account factors such as age and disease severity, the risk of death among CF patients was 34 percent lower in Canada than in the U.S.
The study, funded by the U.S. Cystic Fibrosis Foundation, was conducted at 42 Canadian CF clinics and 110 U.S. CF care centers. It reviewed data from 45,456 patients in the U.S. Cystic Fibrosis Foundation Registry and 5,941 patients in the Canadian Cystic Fibrosis Registry from 1990 to 2013.
In a 2015 research article titled “A contemporary survival analysis of individuals with cystic fibrosis: a cohort study,“ Stephenson noted that Canadians with CF were living almost 20 years longer than they did two decades ago, with a median survival age of 49.7 years in 2012, a massive improvement from 31.9 years in 1990.
Since the article was written, she has updated the median survival age to include data from 2013, reporting that the median age of survival in Canada had reached 50.9 years.
Contributing factors
While the latest study was not designed to explain the CF lifespan disparity between the neighboring countries, Dr. Stephenson suggested several possible contributory factors, including the rate of transplants, diet and nutrition, and universal single-payer public medicare in Canada as opposed to the medical insurance hodgepodge in the U.S.
Lung transplants are one of a very few CF treatments that have an almost immediate impact on survival, and according to Stephenson, a greater proportion of CF patients in Canada received transplants compared to the U.S. during the study period (10.3% in Canad vs. 6.5% in the U.S.).
Also, the respective survival rate difference spike in 2005 coincided with the date the U.S. began using lung allocation scores to prioritize lung transplant waiting lists (a system not used in Canada), which may also be contributing to the lifespan gap.
Diet plays a role
Stephenson also noted that Canadian CF patients were recommended to eat a high-fat diet in the 1970s, a development not adopted by the U.S. until the 1980s. The theory is that a higher caloric intake results in better nutritional support for people with CF, a factor that has been associated in previous studies with improved survival rates.
Consequently, Canadians born in the 1970s who have received optimum nutrition from birth could account for why Canadian survival rates began improving in 1995, implying that CF survival expectancies in countries where more aggressive nutritional support has been implemented in later decades could begin seeing lifespan improvement in the near future.
The insurance factor
The study found no survival rate difference between U.S. CF patients who have private health insurance compared to Canadians with their universal, publicly-funded healthcare system. However, the researchers found that Canadians had a 44 percent lower risk of mortality compared to U.S. patients who are dependent on continuous Medicaid or Medicare; a 36 percent lower risk than those receiving intermittent Medicaid or Medicare; and a 77 percent lower risk of death than CF patients in the U.S. with unknown or no health insurance.
“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 Dr. Bruce Marshall, senior vice president of clinical affairs and lead study investigator 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 CF in the United States,” he said.
Dr. John Wallenburg, chief scientific officer for Cystic Fibrosis Canada, said the “fight against cystic fibrosis is a global one.”
“We are proud that Canadians with this disease are living longer than ever before,” he said. “International collaborations such as the one described in this publication have the potential to help advance care for people living with CF not only in Canada and the U.S., but other countries as well.”