Differences in survival between adults with cystic fibrosis (CF) in Canada and the U.S. likely are explained by a delayed introduction of nutritional support for patients, according to a recent study.
However, the findings, presented at the 30th Annual North American Cystic Fibrosis Conference (NACFC), held in Orlando, Florida Oct. 27-29, also included encouraging data showing that gaps in nutrition and lung function between Canadian and U.S. patients are closing.
The study “Closing The Gap Between Canada And The US: Longitudinal Improvements In Nutrition And Lung Function,” was part of the “Epidemiology in CF” session on the last day of the NACFC meeting.
Studies have shown that patients in Canada with CF live for a median of 10 years longer than U.S. patients. Since both nutritional status and, in the extension, lung function, predict the survival in CF, Anne Stephenson, MD, PhD, of St. Michael’s Hospital in Canada, decided to explore if differences in these parameters could explain the survival gap between the countries.
Stephenson analyzed data from CF registries from the U.S. and Canada, using information gathered between 1990 and 2013. For each year, the percent of expected forced expiratory volume in one second (FEV1, a lung function measure) and body mass index (BMI percentiles for children), was calculated for each country. Patients were divided into three age groups: 6-19 years, 20-40 years, and more than 40 years.
The study used data from 7,940 Canadian and 55,054 American CF patients. In 1990, the median values for FEV1 and BMI were higher in Canada in all three groups. The largest difference in lung function was noted in people older than 40.
Nevertheless, both BMI and lung function improved at a higher rate in patients of all ages in the U.S. The gap in lung function disappeared in 2009 among patients aged 20-40, and in 2003 among children and adolescents. In the oldest patients, however, a gap remained until the end of the study.
The study revealed similar trends for nutrition. However, better nutrition also was seen to benefit the oldest patients, in which the difference disappeared by 2012. Also, during the most recent period, U.S. children had higher BMI than Canadian children.
Researchers believe that the data reflect the fact that Canada introduced improved nutritional support for CF patients in the 1970s, while such interventions were not established in the U.S. until the late 1980s.