Introduction: Lung diffusion capacity (D LCO) declines with age. A significant proportion of older endurance athletes develop exercise-induced hypoxemia (SaO2<95%).

Aim:We hypothesised that master endurance athletes have a lower D LCO than age-matched non-athletes.

Matherial and method: We recruited 166 male endurance elite alhletes who competed in international level (80 young; 86 old) and the same number of age mached sedentary control (82 young; 84 old). Nine different endurance sports disciplines were included in the study. To measure D LCO the participant exhaled to residual volume and then quickly inhaled to ? 90% total lung capacity from a gas source with 0.3% carbon monoxide. The DLCO and transfer coefficient (K CO) were corrected for the actual haemoglobin concentration.

Results:Spirometric function was similar in athletes and age-matched controls. D LCO and K CO were 39% and 31% lower in old and young controls, respectively (P<0.001). Although predicted D LCO and K CO were 11%-points higher in athletes than age-matched controls (P<0.001), they were 25% and 18% lower in old athletes than young controls, respectively (P<0.001).

Conclusion:D LCO did not correlate with age-graded performance or weekly training hours. The better lung diffusion capacity in male endurance athletes than age-matched controls might be an adaptation to training, self-selection and/or attrition bias. However, the diffusion capacity of the older athlete is lower than that of the young non-athlete.