Abstract
The Global Lung Initiative (GLI 2012) recently developed new multi-ethnic reference values for spirometry, based on cross-sectional data sets and covering the age range of 3 to 95 years (Quanjer et al., Eur Respir J. 2012, 40(6):1324-43). The equations are less reliable for subjects aged >75 years and it is unknown if these cross-sectionally based values are suitable for the evaluation of longitudinal data. The SALIA-study (Study on the influence of Air pollution on Lung function, Inflammation and Aging) (Schikowski et al., Respir Res. 2010, 11:113) is a population-based cohort study in elderly women (age at baseline 55 years) with lung function measurements at baseline (1985-1990) and follow-up (2008-2009) covering more than 20 years performed in a rural reference area and the Rhine-Ruhr Basin of Germany.
We analyse whether the GLI reference values fit to the SALIA reference population and evaluate if the GLI values can be used to describe longitudinal change in lung function during aging.
In the reference population the mean GLI-z-score (SD) for FVC was 0.04 (0.94) at baseline (n=709) and 0.33 (0.94) at follow-up (n=355). For FEV1 the mean z-score (SD) at baseline was -0.11 (1.04) and 0.25 (1.01) at follow-up. Only considering the baseline population with follow-up measurement (n=333) the mean GLI-z-score (SD) at baseline for FVC was 0.11 (0.96) and for FEV1 -0.04 (0.96).
The differences between the SALIA reference population and the GLI values are not physiologically relevant (|mean z-scores|<0.5). At age 55 years the values fit almost perfectly, at age 75 years they exceeded GLI values slightly, most likely due to healthy survivor bias in this cohort of elderly women.
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