Alternative ways of expressing FEV1 and mortality in elderly people with and without COPD

Abstract

Expressing forced expiratory volume in 1 s (FEV1) as % predicted relies on the assumption of proportional variability and generalisability of prediction equations that may be unrealistic, especially for elderly people. We evaluated the prognostic implications of alternative ways of expressing FEV1. We enrolled 318 patients with chronic obstructive pulmonary disease (COPD) and 475 controls in the Salute Respiratoria nell'Anziano (SARA) study. The risk for 5-, 10- and 15-year mortality associated with FEV1 was studied by expressing FEV1 % pred, standardised by height cubed (FEV1 · Ht(-3)) and as a multiple of the sex-specific first percentile (FEV1 quotient (FEV1Q)). In the group with COPD, the incidence rate ratio for the worst versus the best quintile of FEV1Q was 4.65 (95% CI 2.33-10.37), compared to 2.98 (1.53-6.27) for FEV1 % pred and 3.95 (2.01-8.45) for FEV1 · Ht(-3). The corresponding incidence rate ratios at 15 years were 4.52 (2.84-7.43), 3.16 (2.02-5.07) and 3.52 (2.25-5.63), respectively. In the control group, even moderate reduction of FEV1Q was associated with long-term mortality, while FEV1 % pred was not associated with the outcome. FEV1Q may be more informative about prognosis in an elderly population compared to FEV1 % pred.