Cystic Fibrosis Patients Survive Ten Years Longer in Canada than in US Interview with:
Dr. Anne L. Stephenson, MD, PhD

St. Michael’s Hospital
Toronto Canada What is the background for this study? What are the main findings?

Response: Both Canada and the US have maintained national registries on individuals with cystic fibrosis (CF) dating back to the 1970s. Previous reports suggested that survival differed between the two countries however direct comparisons of survival estimates between national registry reports were limited because of differences in methodologies used, data processing techniques and possible differences in the patients captured within each registry.

We aimed to compare survival in  cystic fibrosis between Canada and the US to determine if differences existed when we applied a systematic and standardized approach.

Our analysis showed that between 1990 and 2013, survival for individuals with CF increased in both countries, however, the rate of increase was faster in Canada compared to the USA. The survival gap widened at two distinct time points: 1995 and 2005.

In the contemporary period between 2009 and 2013, the median age of survival for individuals with cystic fibrosis in Canada was found to be 50.9 years compared to 40.6 years in the US. Overall, the risk of death was 34% lower for Canadians compared Americans with CF after adjusting for markers of disease severity. When US CF subjects were classified by insurance status, we found a 77% lower risk of death among Canadians with CF compared to Americans who indicated unknown or no insurance, a 44% lower risk compared to Americans receiving continuous Medicare/Medicaid, and a 36% lower risk in Canadians compared to Americans receiving intermittent Medicare/Medicaid. The risk of death for Americans with private insurance was not statistically different from that of Canadians with cystic fibrosis . What should readers take away from your report?

Response: There is a significant gap in cystic fibrosis survival between Americans and Canadians that cannot be explained by differences in statistical methodologies or patient characteristics. The results were consistent across multiple sub-group analyses.

Although our study was not designed to answer the question of why the Canadian survival advantage exists, analyzing the data has generated a few hypotheses that require further testing. Few therapies immediately impact survival with the exception of lung transplantation. Our data showed that there were proportionally more transplants in Canada compared to the US. There is also a substantial difference between how people are prioritized on the transplant list between the two countries. The US system for prioritization on the list was put in place in 2005 which is the point at which the survival gap widened significantly. This system is not used in Canada.

The differences between the health care systems is another possible contributing factor suggested by the differences in survival by US health insurance status compared to Canadians.

Finally, the different approach to nutrition implemented in Canada in the 1970s may be impacting the health of individuals later in life. The high fat diet was implemented in the US about a decade later. What recommendations do you have for future research as a result of this study?

Response: Additional research is required in order to understand the factors that contribute to the survival gap identified in our study. We are continuing to examine differences in health outcomes in  cystic fibrosis between Canada and the US. Both countries are examining the role of transplant in survival and the US CF Foundation has launched an initiative to improve lung transplant outcomes for individuals with CF in the US. Is there anything else you would like to add?

Response: This study was funded by a research grant from the US CF Foundation. Thank you for your contribution to the community.


Survival Comparison of Patients With Cystic Fibrosis in Canada and the United States
A Population-Based Cohort Study

Anne L. Stephenson, MD, PhD; Jenna Sykes, MMath; Sanja Stanojevic, PhD; Bradley S. Quon, MD, MSc; Bruce C. Marshall, MD; Kristofer Petren, BA, BSc; Josh Ostrenga, MSc; Aliza K. Fink, DSc; Alexander Elbert, PhD; Christopher H. Goss, MD, MSc
Annals of Internal Medicine 14 MARCH 2017

Note: Content is Not intended as medical advice. Please consult your health care provider regarding your specific medical condition and questions.

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