CT Shows Exercise Reduces Long-Term Risk of Airway Disease

Maintaining cardiorespiratory fitness can reduce a patient’s risk for developing bronchiectasis later in life.

In a new article published April 27 in Radiology, a team of investigators from Harvard Medical School and Brigham and Women’s Hospital revealed that staying active and maintaining an elevated level of cardiorespiratory fitness can reduce the risk of developing the disease – which causes inflammation, enlarged airways, scarring, and structural damage – by more than 10 percent.

“These results amplify the benefits of fitness to human health when a sedentary lifestyle is a concerning world epidemic,” said lead author Alejandro A. Diaz, M.D., MPH, assistant professor of medicine at Harvard Medical School and associate scientist in pulmonary and critical care medicine at Brigham and Women’s. “It also highlights that fitness might be a tool to preserve lung health. The airways are challenged by what we breathe in every minute, and fitness may help to preserve lung health from injuries.”

CT scans are typically used to confirm or rule out bronchiectasis when a patient presents with shortness of breath or mucus congestion. But, to date, little has been determined about how cardiorespiratory fitness impacts a patient’s risk of developing the disease.

To answer this question, Diaz’s team conducted a secondary analysis of a prospective observational study designed to examine coronary artery disease risk factors in young people – the Coronary Artery Disease in Young Adults (CARDIA) study that began in 1984. For their investigation, they focused on 2,177 healthy adults between ages 18 and 30, following them for 30 years and conducting both fitness tests and CT scans.

They captured fitness levels at year 0 and year 20 by having participants walk on a treadmill for nine 2-minute stages of increasing difficulty. Individuals began at 3 mph at a 2-percent incline and progressed to 5.6 mph at a 25-percent incline. Diaz’s team compared the differences in performance, and they also captured images of the participants at year 25 using a non-contrast electrocardiography-gated CT. The images were reconstructed at 2.5-3 mm section thickness.

According to their analysis, 209 participants (9.6 percent) had developed bronchiectasis at year 25. From what they saw, having a higher level or cardiorespiratory fitness was protective and reduced the patient’s risk.

“In an adjusted model, one minute longer treadmill duration between year zero and year 20 was associated with 12-percent lower odds of bronchiectasis on CT at year 25,” Diaz said. “Having preserved fitness at middle age is associated with lower chances of bronchiectasis.”

Specifically, the team saw a drop in bronchiectasis prevalence among both men and women as their cardiorespiratory fitness improved. For men, incidence of the disease dropped from 13.2 percent for males who had sustained low fitness to 7.1 percent for those who had sustained high fitness. Women were similar – rates dropped from 13.2 percent for individuals with sustained low fitness to 5.6 percent for those with sustained high fitness.

Overall, the team learned bronchiectasis appeared more often in the lower lobes (130 of 209 – 62.2 percent), followed by the middle and lingula (105 of 209 – 50.2 percent) and the upper lobes (33 of 209 – 15.8 percent). In addition, they discovered that interleukin-6 was directly related to bronchiectasis at CT, contributing 11 percent to the 20-year fitness change effect on the odds of the disease being present on the 25-year CT scan.

The team did note, however, that their results pinpointed a higher incidence of bronchiectasis than the previously reported level – 9.6 percent compared to 0.043 percent, respectively. The difference likely exists, they said, because they used CT to detect bronchiectasis rather than relying solely on physician-based diagnoses.

“This study suggests that bronchiectasis on CT scans might be more frequent than previously that,” Diaz said. “However, the clinical implications of finding bronchiectasis on CT scans in people with no or mild symptoms remains to be determined.”

This link between cardiorespiratory fitness and bronchiectasis reduction could exist for several reasons, they explained. First, high cardiorespiratory fitness is already associated with lower levels of systemic inflammation, helping to preserve airway health. Second, it also lowers the risk of other bronchiectasis-associated diseases, including asthma and pneumonia. And, lastly, maintaining a high level of cardiorespiratory fitness improves a patient’s ability to clear his or her airway of mucus.

The results of this study are compelling said Jadranka Stojanovska, M.D., MS, assistant professor of radiology and director of the cardiothoracic MRI program at Michigan Medicine.

“The corollary of these results suggests that high cardiorespiratory fitness decreases systemic and airway inflammation improves the capacity and efficiency of cardiorespiratory systems with improved airway perfusion, including mucociliary system, and, therefore, prevents the development of bronchiectasis,” she said in an accompanying editorial. “These results also add decreased risk of bronchiectasis to the myriad of health benefits achieved by staying fit.”

Clinically, she said, the findings could be impactful because they could affect the use of preventive strategies that can increase cardiorespiratory fitness. In fact, she said, the study outcomes highlight the need for personalized preventive treatments for patients with sedentary lifestyles.

Diaz’s team agreed the results could be beneficial at the clinical level.

“The underlying premise is that improving cardiorespiratory fitness presents health professionals with unique opportunities to encourage lifestyle-based strategies designed to reduce the risk of respiratory diseases, including bronchiectasis,” the team said.

Still, the study does leave behind lingering questions, Stojanovska said. Does baseline cardiorespiratory fitness predict bronchiectasis presence at year 25? Is there a minimum treadmill duration that is protective against clinical and radiologic bronchiectasis? And, how does cardiorespiratory fitness affect quality of life for patients who develop the disease?

As a next step, Diaz's team is already studying bronchiectasis with other populations, such as smokers, to learn more about the presentation of the disease.

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