Higher Levels of Cardiorespiratory Fitness Associated With Lower Long-Term Risk of COPD

Higher levels of cardiorespiratory fitness (CRF) are associated with lower long-term risk of chronic obstructive pulmonary disease (COPD) for middle-aged men, according to a new study.

Studying over 4000 men for up to 46 years, the researchers are the first to determine the relationship between CRF and very long-term risk of COPD among healthy middle-aged men. The long-term data revealed that men with high levels of CRF were 31% less likely than men with low levels of CRF to have COPD. Men with normal CRF were 21% less likely. Time to diagnosis of COPD was delayed by 1.79 years for normal CRF levels and by 1.8 years for high CRF levels.

Higher levels of CRF also yielded benefits for risk of death due to COPD, with study data revealing that high levels of CRF resulted in 62% decreased risk and normal levels of CRF resulted in 35% decreased risk compared with low levels of CRF.

These findings remained largely unchanged even after excluding the 386 men who were diagnosed with and died from COPD during the first 10 years of follow-up.

The men in the study were recreuited between 1970 and 1971, and CRF was determined as the maximal oxygen uptake capacity by ergometer test. During follow-up, 626 (13.2%) men were diagnosed with COPD and 233 (4.9%) died as a result of COPD. Men who had lower levels of CRF had higher body mass index, higher alcohol consumption, lower socioeconomic status, and higher incidence of diabetes and arterial hypertension.

“The mechanisms that connect CRF with the development and progression of COPD are unknown,” wrote the researchers. “CRF is a pivotal physiological indicator of the integrated ability if the cardiac, pulmonary, muscular, and cellular systems to transport oxygen from the inspired air to the mitochondria and produce adenosine triphosphate as the fuel for physical activity.”

To date, no studies have examined the link between CRF and COPD; however, several studies have suggested that high levels of physical activity may reduce lung function decline, thus delaying the progression of COPD.

Other potential mechanisms connecting the 2 include the notion that low-grade systemic inflammation could play a role. Physical inactivity is associated with high levels of markers of systematic inflammation, such as elevated levels of high-sensitivity C-reactive protein, fibrinogen, and interleukin 1 and 6. Meanwhile, regular physical activity reduces systemic inflammation and oxidative stress.

“Earlier studies have shown that increased levels of inflammatory markers are related to poorer prognosis of COPD due to increased number of exacerbations, higher prevalence of comorbidities, and higher mortality,” added the researchers. “Therefore, it is plausible that higher levels of physical activity among individuals with high levels of CRF can affect COPD development and progression.”

In the current study, the researchers were unable to study the relationship due to the lack of spirometric data in the cohort and the use of objectively measured CRF rather than self-reported physical activity.

Reference:

Hansen G, Marott J, Holtermann A, Gyntelberg F, Lange P, Jensen M. Midlife cardiorespiratory fitness and the long-term risk of chronic obstructive pulmonary disease [published online June 17, 2019]. Thorax. doi: 10.1136/thoraxjnl-2018-21282.