Respiratory impairment and COPD hospitalisation in older persons: a competing risk analysis.

The aim of the present study was to evaluate, among older persons, the association between respiratory impairment and hospitalisation for chronic obstructive pulmonary disease (COPD), based on spirometric Z-scores, i.e. the LMS (lambda, mu, sigma) method, and a competing risk approach. Using data on 3,563 white participants aged 65-80 yrs (from the Cardiovascular Health Study) we evaluated the association of LMS-defined respiratory impairment with the incident of COPD hospitalisation and the competing outcome of death without COPD hospitalisation, over a 5-yr period. Respiratory impairment included airflow limitation (mild, moderate or severe) and restrictive pattern. Over a 5-yr period, 276 (7.7%) participants had a COPD hospitalisation incident, whereas 296 (8.3%) died without COPD hospitalisation. The risk of COPD hospitalisation was elevated more than two-fold in LMS-defined mild and moderate airflow limitation and restrictive pattern (adjusted HR (95% CI): 2.25 (1.25-4.05), 2.54 (1.53- 4.22) and 2.65 (1.82-3.86), respectively), and more than eight-fold in LMS-defined severe airflow limitation (adjusted HR (95% CI) 8.33 (6.24-11.12)). Conversely, only LMS-defined restrictive-pattern was associated with the competing outcome of death without COPD hospitalisation (adjusted HR (95% CI) 1.68 (1.22-2.32)). In older white persons, LMS-defined respiratory impairment is strongly associated with an increased risk of COPD hospitalisation. These results support the LMS method as a basis for defining respiratory impairment in older persons.