The cut-off for forced expiratory volume in 1 s (FEV1)/forced vital capacity (FVC) defining airflow limitation for chronic obstructive pulmonary disease (COPD) is still contested. We assessed airflow limitation prevalence by the lower limit of normal (LLN) of Global Lungs Initiative (GLI) 2012 reference values and its predictive ability for all-cause mortality and hospitalisation in very old adults (aged ≥80 years) compared with the fixed cut-off. In a Belgian population-based prospective cohort of 411 very old adults, airflow limitation prevalence by the 5th percentile of GLI 2012 z-scores (GLI-LLN) and fixed cut-off (0.70) were compared with COPD reported by general practitioners (GPs). Survival and Cox regression multivariable analysis assessed the association of airflow limitation by both cut-offs with 5-year all-cause mortality and first hospitalisation at 3 years. 9.2% had airflow limitation by GLI-LLN and 27% by fixed cut-off, without good agreement (kappa coefficient ⩽0.40) with GP-reported COPD (9%). Only airflow limitation by GLI-LLN was independently associated with mortality (adjusted hazard ratio 2.10, 95% CI 1.30-3.38). FEV1/FVC