Good cardiorespiratory fitness in midlife may lower the risk of developing and dying from COPD, a prospective cohort study from Denmark has found.

The Copenhagen Male Study recruited 5,286 men aged 40-59 years, mean 48.7, from 14 large workplaces in the city from 1970 to 1971.

The men completed a questionnaire and were asked to describe themselves as never smokers, former smokers or active smokers. Tobacco consumption was calculated from the number of cigarettes smoked a day. Leisure time physical activity was self-reported as low, moderate or high. Those with preexisting COPD, asthma or chronic cough symptoms were excluded.

VO₂ max was measured by standard bicycle ergometer test to determine cardiorespiratory fitness. Categories of cardiorespiratory fitness (low, normal, high) were defined as ± 1 Z-score (± 1 SD) above or below the age-adjusted mean.

The study endpoints were incident COPD, and death from COPD.

The sensitivity analyses included tests for reverse causation, which were performed by excluding participants who died within ten years of recruitment.

Participants were followed up for up to 46 (mean 28.3) years. Of 4,730 participants, 4,338 (91.7%) had died by the end of the study. There were 626 (13.2%) participants diagnosed with COPD, and 233 (4.9%) were registered with COPD as a cause of death.

Poor cardiorespiratory fitness was associated with lower levels of self-reported physical activity, higher body mass index, higher alcohol consumption, lower socioeconomic status, and higher incidence of diabetes and arterial hypertension.

An age-adjusted Cox proportional hazard model demonstrated a reduced risk of incident COPD with increased levels of cardiorespiratory fitness. When compared with low cardiorespiratory fitness, the risk of incident COPD was reduced by 18% in participants with normal cardiorespiratory fitness; HR 0.82 (95% CI: 0.66-1.01, P = 0.07), and by 22% for participants with high cardiorespiratory fitness; HR 0.78 (95% CI: 0.60-1.02, P = 0.08).

The age-adjusted risk of death from COPD, relative to low cardiorespiratory fitness, was estimated to be reduced by 27% in participants with normal cardiorespiratory fitness; HR 0.73 (95% CI: 0.52-1.01, P = 0.058) and by 50% in participants with high cardiorespiratory fitness levels; HR 0.50 (95% CI: 0.32-0.80, P = 0.003).

Higher levels of cardiorespiratory fitness were associated with a delay to both diagnosis of COPD and death from COPD. Time to diagnosis was delayed by 1.79 years for men with normal vs low cardiorespiratory fitness (95% CI: 0.14-3.45, P = 0.034), and 1.45 years (95% CI: −0.71 to –3.60, P = 0.19) for those with high vs low cardiorespiratory fitness.

Death from COPD was delayed by 1.28 years (95% CI: 0.04-2.52, P = 0.042) for normal vs low cardiorespiratory fitness, and by 1.8 years (95% CI: 0.19-3.42, P = 0.028) for high vs low cardiorespiratory fitness. Tests for reverse causation did not alter the results.

While no previous studies have examined the association between cardiorespiratory fitness and COPD specifically, several studies have suggested that high levels of physical activity may reduce decline in lung function thereby delaying the progression of COPD. This study offers good evidence in support of that premise.

The message to all individuals at risk from COPD is that maximising cardiorespiratory fitness from middle age onwards can effectively reduce the risk of developing or dying from the condition.

The study authors conclude:

‘In individuals at risk of developing COPD, fitness enhancing physical activity should be encouraged not only to reduce dyspnoea but also to delay development, progression and death from COPD.’

Dr Peter Saul