Study finds differences in lifespan between Canadians and Americans with cystic fibrosis

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Dr. Anne Stephenson, study lead author and respirologist at the Adult Cystic Fibrosis Center of St. Michael's Hospital in Toronto, believes several factors may influence the discrepancy between the two countries.

Canadians with cystic fibrosis, a life threatening inherited disorder of the lungs and digestive system, tend to survive about a decade longer than American patients, a new study suggests. Canada uses a different allocation criteria, based more on doctors' subjective assessment of an individual patient's critical need for a transplant.

Since the early 1970s, both nations have maintained cystic fibrosis patient data registries.

"We're about finding the best care wherever it is and trying to understand, if Canada's got better outcomes, how do they do that so we can copy it", said Dr. Bruce Marshall of the U.S. Cystic Fibrosis Foundation, which funded the study.

Research showed the median survival age recorded in Canada between 2009 and 2013 was 50.9 years, whereas USA patient registries documented an average life expectancy of only 40.6 years.

"We don't know what the cause is, but we hypothesized that there are certain factors that may be contributing to the differences between the two countries".

Results indicated a strong "survival gap" during the later years of the study as well.

But the differences aren't just about math - they're real, the researchers soon discovered.

After taking into account factors like patient age and disease severity, researchers found the risk of death among people with CF was 34 per cent lower in Canada than in the United States. The 10-year difference in lifespan was based on data from the last five years.

In an accompanying editorial, Dr. Patrick Flume of the Medical University of SC and Donald VanDevanter of Case Western Reserve University applauded the study, saying researchers now must find and implement solutions to bridge the survival gap, "which seems to be based on fundamental differences in the two nations' health-care systems".

She has received personal fees from Cystic Fibrosis Canada for work unrelated to this study.

"We used insurance status as a surrogate marker for the USA health care system compared to the universal health care system in Canada", Stephenson said by email.

-A higher proportion of Canadian CF patients receive a life-prolonging lung transplant, 10.3 percent compared to 6.5 percent of USA patients.

In 2005, when the United States began using a lung allocation score to prioritize people on the transplant waiting list, the survival gap also increased dramatically, the authors noted.

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

"So we're thinking the effect of that may be a bit delayed in the USA because of the different approaches to nutrition in those early days", Stephenson said.

Half of the Canadians survived past age 51, whereas half of the USA patients had died by age 41.

In the study group, Canadian CF patients as a whole had a 77 per cent lower risk for death than US patients with no health insurance or who health insurance status was unknown.

However, Canadians had a 44 percent lower risk for death than USA patients receiving continuous Medicaid or Medicare, a 36 percent lower risk than those receiving intermittent Medicaid or Medicare coverage, and a 77 percent lower risk than those with unknown or no health insurance.

Overall, the risk for death was 34 percent lower in Canada than in the USA, researchers report in the Annals of Internal Medicine. "The impact of US health insurance/health care policy and survival in U.S".

One of them was Canada's adoption in the 1970s of a high-fat, high-calorie diet that resulted in patients being better nourished, said Stephenson, director of the Canadian Cystic Fibrosis Registry. People with cystic fibrosis also have difficulty properly breaking down and absorbing nutrients from food, the researchers explained. The high-fat diet, which increases nutritional absorption, prevents malnutrition and so probably helps explain improved survival rates north of the border starting in 1995, Stephenson said.

Dr. Stephenson says that while it is good that Canadian CF patients have a higher median life expectancy than they did a few decades ago, it is still lower than the average person. "This approach to nutrition was adopted by the U.S.in the 1980s and is considered standard of care for CF patients worldwide". This score is not used in Canada. "(U.S.) Medicaid and Medicare together had a similar effect to Canadians, but not as dramatic.