Association of obstructive sleep apnoea with exercise capacity and mortality in a population-based study: results of...

Sleep and physical fitness are interrelated, with cardiovascular risk factors potentially influencing this relationship. Sleep disturbances and reduced exercise capacity are linked to higher mortality. This study examined associations between sleep characteristics, cardiopulmonary exercise testing (CPET) measures and all-cause mortality, and assessed whether reduced exercise capacity mediates the link between impaired sleep and mortality.

We analysed 1001 participants from the population-based SHIP-TREND cohort (2008-2012) who underwent single-night polysomnography and symptom-limited CPET. Associations between sleep and CPET measures, as well as mortality, were assessed using multivariable linear and Cox regression models.

The mean age of participants was 54 (range 44-63) years; 47.1% were women. The apnoea-hypopnoea index (AHI) was 4.9 (95% CI 1.4-13.7) events·h^-1 and higher in men (7.9, 95% CI 2.6-18.8) than in women (2.6, 95% CI 0.7-9.2; p<0.001). Peak oxygen uptake (V'_{O2 peak}) was lower in women (22 (95% CI 18-25) mL·min^-1·kg^-1) than in men (27 (95% 22-32) mL·min^-1·kg^-1; p<0.001). Higher AHI and oxygen desaturation index were inversely associated with V'_{O2 peak}. Over a median 10.3-year follow-up, 73 deaths occurred. AHI was significantly associated with all-cause mortality across models (hazard ratio 1.31-1.72). Mediation analysis demonstrated a significant direct effect, whereas the indirect effect via V'_{O2 peak} was not statistically significant.

In the SHIP-TREND-0 cohort, elevated AHI is associated with reduced V'_{O2 peak} and increased all-cause mortality. Mediation analysis suggested a possible, but not statistically significant, contribution of impaired cardiopulmonary fitness to the relationship between sleep apnoea and mortality, highlighting a potential role of fitness that warrants further investigation.