Alternative ways of expressing forced expiratory volume in the first second and long-term mortality in elderly patients with asthma

Background Clinical and epidemiologic evidence on asthma in the elderly is scant. There is evidence that forced expiratory volume in the first second (FEV₁), a commonly used indicator of overall pulmonary function, might not be an independent predictor of 5-year mortality in elderly patients with asthma. Objective To investigate the association between FEV₁ expressed using 3 alternative methods and 5-, 10-, and 15-year mortality in a population of elderly patients with asthma. Methods Participants in the Salute Respiratoria nell' Anziano study were included. Asthma was diagnosed at baseline according to spirometric and clinical data. Vital status at 15 years was assessed using death registries. FEV₁ was expressed as percentage of predicted, divided by height cubed, and as a multiple of the sex-specific first percentile. The association between FEV₁ and mortality was evaluated using Cox proportional hazard models. Results Two hundred patients were studied (52% women, mean age 73.1 years, standard deviation 6.2 years). All FEV ₁ measurements were associated with mortality at unadjusted analysis. After correction for potential confounders, no association was found between FEV₁ and 5-year mortality. Only FEV₁ as a multiple of the sex-specific first percentile was independently associated with 10-year (hazard ratio 0.35, 95% confidence interval 0.14-0.87) and 15-year (hazard ratio 0.38, 95% confidence interval 0.19-0.79) mortality. Conclusion Although extensively used, FEV₁ expressed as percentage of predicted does not seem to be the best predictor of mortality in elderly patients with asthma. Although no spirometric index can predict 5-year mortality in this population, FEV ₁ as a multiple of the sex-specific first percentile should be considered when longer-term prognostic stratification is needed.