Exercise as it relates to Disease/The importance of aerobic fitness in patients with Cystic Fibrosis

Nixon, A Patricia., Orenstein, M David., Kelsey, F Sheryl., Doershuk, F Carl. (1992) The Prognostic Value of Exercise Testing in Patients with Cystic Fibrosis. The New England Journal of Medicine. Pages 1785 – 1788.

1. What is the background to this research?
The Prognosis value of exercise testing in patients with cystic fibrosis (Nixon, 1992) is a journal article focusing on the link between aerobic fitness and mortality in cystic fibrosis patients. This study was an extremely important medical breakthrough showing there is a significant relationship between aerobic fitness and enhanced health outcomes in individuals with cystic fibrosis, and has been supported by many recent studies.

Prior to the release of this study in 1992, there was limited research looking into impacts of cystic fibrosis. The only other related study was one conducted on cystic fibrosis patients over 3 years with a 26 month follow up period to investigate differences between mortality and respiratory function in individuals using the humidified oxygen or air concentrators overnight. This study concluded there were no difference in the groups in terms of mortality, progression of the disease and/or hospitalization.

Following these studies there has been many related studies conducted and released since.

2.      Where is the research from?
This study was published in The New England Journal of Medicine and was conducted in Pittsburgh, Pennsylvania, USA. This is a peer reviewed journal that is a highly reputable and reliable source of scientific articles, including 2,167 articles on cystic fibrosis.

All the authors of this article are well respected with many of them working at universities and/ or being doctors in fields related to cystic fibrosis (e.g., pediatrics pulmonary).

There are no organizations or sponsorships that may influence or bias the results.

3.      What kind of research was this?
This study was a longitudinal study that was conducted in the late 1970s as individuals were followed over 8-years to assess how their condition/ health developed over this period. The calculation of survival rates was done with the standard life-table methods, and then Chi-square analysis was used to establish whether there was a significant trend in the participants that died in the 8-year follow up.

A similar level of evidence has been shown through the benefits of aerobic fitness on lung functions and reduced mortality in many other studies. As demonstrated by one published in 2020 showing exercise is used with patients with cystic fibrosis to act as an airways clearance technique that enhances the elimination of mucosal cilia. Another study claimed enhanced exercise capacity is related to a greater quality of life in patients with cystic fibrosis.

4.      What did the research involve?
This study included 109 participants, aged 7-35 years with cystic fibrosis. These participants performed pulmonary function and progressive exercise testing on electronically braked cycle ergometers. These tests consisted of starting at 0 watts then increase by 10-20 watts each minute until the participants physically could not continue (VO2max test).

The method used was innovative to obtain baseline values and their relationship to mortality over the following 8 years as this type of testing had not been done before in relation to cystic fibrosis. The participants were put into groups depending on their VO2 peak and examined survival rates for the different aerobic groups.

5.      What were the basic results?
One of the most important findings from this study was that in the 8 years follow up period the individuals characterized as having the greatest aerobic fitness had at least an 82% chance of survival while the individuals characterized as having the lowest aerobic fitness only had a 28% chance of survival. There was a greater risk of mortality with lower aerobic fitness, lower SAO2, lower pulmonary function and high-end tidal volume according to the univariate analysis. Individuals were more than 3 times as likely to die if they were categorized as the lowest fitness group compared to the highest.

The researchers concluded that there is a significant relationship between survival in patients with cystic fibrosis and aerobic fitness (VO2peak).

6.      What conclusions can we take from this research?
This study has demonstrated the importance of aerobic fitness which is both an environmental and genetic (30%) factor. This study shows there is a strong correlation between enhanced aerobic fitness and increased lifespan with individuals with cystic fibrosis, although more research is needed to further look into this conclusion.

More recent research has supported the findings of this study as they also showed that there is a strong relationship between aerobic fitness and respiratory health of individuals with cystic fibrosis.

This study could have been further enhanced by placing individuals into different exercise groups for an extended period and see what effect this had on their aerobic fitness and overall mortality. The analysis presented in the article could have been strengthened by conducting multivariate analysis to test whether there was a significant relationship between mortality, aerobic fitness, and age, given that older patients (those over 25 years of age) are are at increased risk of mortality than younger patients. Further, the article should also have defined the expected VO2peak value and the percentage VO2peak, to enable the results to be compared to other studies that have examined the same issues.

7.      Practical advice
The real-world implication of this research is that aerobic exercise should be prescribed to all individuals with cystic fibrosis to help manage this chronic and deadly disease. This study showed that there is a relationship between aerobic fitness, ventilatory muscle endurance, and cardiovascular efficiency in people with cystic fibrosis. The enhancement of ventilatory muscle endurance can help delay the occurrence of respiratory failure and muscle fatigue. This study showed an association between aerobic exercise training and slowing the progression of this disease, as respiratory failure is the main cause of deaths from cystic fibrosis.

It is important to undertake exercise testing before the commencement of an exercise program. The Godfrey Cycle Ergometer Protocol with ventilatory gas exchange and oxygen saturation monitoring is advised for those undertaking exercise testing over the age of 10. For children with cystic fibrosis it is important that there is ongoing support and encouragement from their health care team and family. It is attainable for relatively healthy cystic fibrosis patients to achieve 30 minutes per day of moderate-vigorous physical activity, although increased amounts are associated with enhanced outcomes over 1 year.

8.      Further information/resources
The diagnosis and treatment of Cystic Fibrosis

Why exercise is used as a intervention for Cystic Fibrosis Patients

Cystic Fibrosis information and support groups for patients and their families

About Cystic Fibrosis: What it is, life with CF, how to get involved and connect with others suffering from this disease and their families.